U.S. patent application number 15/342663 was filed with the patent office on 2017-06-22 for method for automatically adjusting tunable passive antennas, and automatically tunable antenna array using this method.
This patent application is currently assigned to Tekcem. The applicant listed for this patent is TEKCEM. Invention is credited to Frederic BROYDE, Evelyne CLAVELIER.
Application Number | 20170179601 15/342663 |
Document ID | / |
Family ID | 55697249 |
Filed Date | 2017-06-22 |
United States Patent
Application |
20170179601 |
Kind Code |
A1 |
BROYDE; Frederic ; et
al. |
June 22, 2017 |
METHOD FOR AUTOMATICALLY ADJUSTING TUNABLE PASSIVE ANTENNAS, AND
AUTOMATICALLY TUNABLE ANTENNA ARRAY USING THIS METHOD
Abstract
The invention relates to a method for automatically adjusting a
plurality of tunable passive antennas, for instance a plurality of
tunable passive antennas of a radio transceiver using several
antennas simultaneously. The invention also relates to an
automatically tunable antenna array using this method. An
automatically tunable antenna array of the invention has 4 user
ports, and comprises: 4 tunable passive antennas, the 4 tunable
passive antennas operating simultaneously in a given frequency band
and forming a multiport antenna array; 4 sensing units; 4 feeders;
a signal processing unit delivering a tuning instruction; and a
tuning control unit, the tuning control unit receiving the tuning
instruction from the signal processing unit, the tuning control
unit delivering tuning control signals to the tunable passive
antennas, the tuning control signals being determined as a function
of the tuning instruction.
Inventors: |
BROYDE; Frederic; (Maule,
FR) ; CLAVELIER; Evelyne; (Maule, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TEKCEM |
Maule |
|
FR |
|
|
Assignee: |
Tekcem
|
Family ID: |
55697249 |
Appl. No.: |
15/342663 |
Filed: |
November 3, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15337595 |
Oct 28, 2016 |
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15342663 |
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PCT/IB2016/051400 |
Mar 11, 2016 |
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15337595 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01Q 9/0442 20130101;
H01Q 21/00 20130101; H01Q 21/0006 20130101; H04B 1/0458 20130101;
H04B 1/18 20130101; H01Q 21/28 20130101; H01Q 9/14 20130101 |
International
Class: |
H01Q 9/04 20060101
H01Q009/04; H01Q 21/00 20060101 H01Q021/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 17, 2015 |
FR |
1502633 |
Claims
1. A method for automatically adjusting n tunable passive antennas,
where n is an integer greater than or equal to 2, each of then
tunable passive antennas comprising at least one antenna control
device, one or more characteristics of said each of the n tunable
passive antennas being controlled using said at least one antenna
control device, said at least one antenna control device having at
least one parameter having an influence on said one or more
characteristics, said at least one parameter being adjustable by
electrical means, the method comprising the steps of: applying
excitations to m user ports, where m is an integer greater than or
equal to 2, one and only one of the excitations being applied to
each of the user ports, each of the excitations having one and only
one complex envelope, the m complex envelopes of them excitations
being linearly independent in the set of complex functions of one
real variable, regarded as a vector space over the field of complex
numbers, the m user ports presenting, at a given frequency, an
impedance matrix referred to as the impedance matrix presented by
the user ports; estimating q real quantities depending on the
impedance matrix presented by the user ports, where q is an integer
greater than or equal to m, by utilizing the m excitations;
utilizing the q real quantities depending on the impedance matrix
presented by the user ports, to obtain tuning control signals; and
applying each of the tuning control signals to one or more of the
antenna control devices, each of said parameters being mainly
determined by one or more of the tuning control signals.
2. The method of claim 1, wherein two or more of the excitations
are applied simultaneously to the user ports.
3. An automatically tunable antenna array having m user ports,
where m is an integer greater than or equal to 2, the m user ports
presenting, at a given frequency, an impedance matrix referred to
as the impedance matrix presented by the user ports, the
automatically tunable antenna array comprising: n tunable passive
antennas, where n is an integer greater than or equal to 2, each of
the n tunable passive antennas comprising at least one antenna
control device, one or more characteristics of said each of the n
tunable passive antennas being controlled using said at least one
antenna control device, said at least one antenna control device
having at least one parameter having an influence on said one or
more characteristics, said at least one parameter being adjustable
by electrical means; at least m sensing units, each of the sensing
units delivering one or more sensing unit output signals, each of
the sensing unit output signals being mainly determined by one or
more electrical variables; a signal processing unit, the signal
processing unit estimating q real quantities depending on the
impedance matrix presented by the user ports, where q is an integer
greater than or equal to m, by utilizing the sensing unit output
signals obtained for m excitations applied to the user ports, one
and only one of the excitations being applied to each of the user
ports, each of the excitations having one and only one complex
envelope, the m complex envelopes of the m excitations being
linearly independent in the set of complex functions of one real
variable, regarded as a vector space over the field of complex
numbers, the signal processing unit delivering a tuning instruction
as a function of the q real quantities depending on the impedance
matrix presented by the user ports; and a tuning control unit, the
tuning control unit receiving the tuning instruction from the
signal processing unit, the tuning control unit delivering tuning
control signals to the tunable passive antennas, the tuning control
signals being determined as a function of the tuning instruction,
each of said parameters being mainly determined by one or more of
the tuning control signals.
4. The automatically tunable antenna array of claim 3, wherein the
sensing unit output signals delivered by each of the sensing units
comprise: a first sensing unit output signal proportional to a
first electrical variable, the first electrical variable being a
voltage across one of the user ports; and a second sensing unit
output signal proportional to a second electrical variable, the
second electrical variable being a current flowing in said one of
the user ports.
5. The automatically tunable antenna array of claim 3, wherein the
sensing unit output signals delivered by each of the sensing units
comprise: a first sensing unit output signal proportional to a
first electrical variable, the first electrical variable being an
incident voltage at one of the user ports; and a second sensing
unit output signal proportional to a second electrical variable,
the second electrical variable being a reflected voltage at said
one of the user ports.
6. The automatically tunable antenna array of claim 3, further
comprising n feeders, each of the feeders having a first end
coupled to a signal port of one and only one of the tunable passive
antennas, each of the feeders having a second end coupled to one
and only one of the user ports, through one and only one of the
sensing units.
7. The automatically tunable antenna array of claim 3, further
comprising a multiple-input-port and multiple-output-port network
having m input ports, each of the m input ports being coupled to
one and only one of the user ports, through one and only one of the
sensing units.
8. The automatically tunable antenna array of claim 7, wherein the
multiple-input-port and multiple-output-port network is not
composed of a plurality of uncoupled single-input-port and
single-output-port networks.
9. The automatically tunable antenna array of claim 7, wherein the
multiple-input-port and multiple-output-port network is composed of
m uncoupled single-input-port and single-output-port networks.
10. The automatically tunable antenna array of claim 3, further
comprising a multiple-input-port and multiple-output-port tuning
unit having m input ports, each of the m input ports being coupled
to one and only one of the user ports through one and only one of
the sensing units, the multiple-input-port and multiple-output-port
tuning unit comprising p adjustable impedance devices, where p is
an integer greater than or equal to m, the p adjustable impedance
devices being referred to as the adjustable impedance devices of
the tuning unit and being such that, at said given frequency, each
of the adjustable impedance devices of the tuning unit has a
reactance, the reactance of any one of the adjustable impedance
devices of the tuning unit being adjustable by electrical means,
the automatically tunable antenna array being such that the tuning
control unit delivers tuning control signals to the
multiple-input-port and multiple-output-port tuning unit, the
reactance of each of the adjustable impedance devices of the tuning
unit being mainly determined by one or more of the tuning control
signals.
11. The automatically tunable antenna array of claim 10, wherein
the multiple-input-port and multiple-output-port tuning unit has a
plurality of output ports and is such that, at the given frequency,
there exists a diagonal impedance matrix referred to as the given
diagonal impedance matrix, the given diagonal impedance matrix
being such that, if an impedance matrix seen by the output ports is
equal to the given diagonal impedance matrix, then the reactance of
any one of the adjustable impedance devices of the tuning unit has
an influence on an impedance matrix presented by the input
ports.
12. The automatically tunable antenna array of claim 11, wherein
the multiple-input-port and multiple-output-port tuning unit is
such that, at the given frequency, if an impedance matrix seen by
the output ports is equal to the given diagonal impedance matrix,
then the reactance of at least one of the adjustable impedance
devices of the tuning unit has an influence on at least one
non-diagonal entry of the impedance matrix presented by the input
ports.
13. The automatically tunable antenna array of claim 10, wherein
the multiple-input-port and multiple-output-port tuning unit is
composed of m uncoupled single-input-port and single-output-port
tuning units, each comprising one or more of said adjustable
impedance devices of the tuning unit.
14. The automatically tunable antenna array of claim 3, wherein two
or more of the excitations are applied simultaneously to the user
ports.
15. The automatically tunable antenna array of claim 3, wherein the
tuning instruction is such that the impedance matrix presented by
the user ports is substantially equal to a wanted impedance
matrix.
16. The automatically tunable antenna array of claim 3, wherein the
signal processing unit uses a lookup table to determine the tuning
instruction.
17. The automatically tunable antenna array of claim 3, wherein the
signal processing unit delivers the tuning instruction as a
function of said q real quantities depending on the impedance
matrix presented by the user ports, and as a function of one or
more temperatures.
18. The automatically tunable antenna array of claim 3, wherein the
tuning control signals are determined as a function of the tuning
instruction and as a function of one or more temperatures.
19. The automatically tunable antenna array of claim 3, wherein the
tuning instruction is delivered repeatedly.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This is a Continuation Application of PCT application No.
PCT/IB2016/051400, filed 11 Mar. 2016, entitled "Method for
automatically adjusting tunable passive antennas, and automatically
tunable antenna array using this method", which in turn claims
priority to French patent application No. 15/02633 of 17 Dec. 2015,
entitled "Procede pour regler automatiquement des antennes passives
accordables et reseau d'antennes automatiquement accordable
utilisant ce procede", both of which are incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] The invention relates to a method for automatically
adjusting a plurality of tunable passive antennas, for instance a
plurality of tunable passive antennas of a radio transceiver using
several antennas simultaneously. The invention also relates to an
automatically tunable antenna array using this method.
PRIOR ART
[0003] A tunable passive antenna comprises at least one antenna
control device having at least one parameter having an effect on
one or more characteristics of said tunable passive antenna, said
at least one parameter being adjustable, for instance by electrical
means. Adjusting a tunable passive antenna means adjusting at least
one said at least one parameter. Each of said one or more
characteristics may for instance be an electrical characteristic
such as an impedance at a specified frequency, or an
electromagnetic characteristic such as a directivity pattern at a
specified frequency. A tunable passive antenna may also be referred
to as "reconfigurable antenna". Some authors consider three classes
of tunable passive antennas: polarization-agile antennas,
pattern-reconfigurable antennas and frequency-agile antennas. The
state of the art regarding frequency-agile antennas is for instance
described in the article of A. Petosa entitled "An Overview of
Tuning Techniques for Frequency-Agile Antennas", published in IEEE
Antennas and Propagation Magazine, vol. 54, No. 5, in October 2012.
As explained in this article, many different types of antenna
control device may be used to control one or more characteristics
of a tunable passive antenna. An antenna control device may for
instance be: [0004] an electrically controlled switch or
change-over switch, in which case a parameter of the antenna
control device having an effect on one or more characteristics of
the tunable passive antenna may be the state of the switch or
change-over switch; [0005] an adjustable impedance device, in which
case a parameter of the antenna control device having an effect on
one or more characteristics of the tunable passive antenna may be
the reactance or the impedance of the adjustable impedance device
at a specified frequency; or [0006] an actuator arranged to produce
a mechanical deformation of the tunable passive antenna, in which
case a parameter of the antenna control device having an effect on
one or more characteristics of the tunable passive antenna may be a
length of the deformation.
[0007] If an antenna control device is an electrically controlled
switch or change-over switch, it may for instance be an
electro-mechanical relay, or a microelectromechanical switch (MEMS
switch), or a circuit using one or more PIN diodes or one or more
insulated-gate field-effect transistors (MOSFETs) as switching
devices.
[0008] An adjustable impedance device is a component comprising two
terminals which substantially behave as the terminals of a passive
linear two-terminal circuit element, and which are consequently
fully characterized by an impedance which may depend on frequency,
this impedance being adjustable.
[0009] An adjustable impedance device having a reactance which is
adjustable by electrical means may be such that it only provides,
at a given frequency, a finite set of reactance values, this
characteristic being for instance obtained if the adjustable
impedance device is: [0010] a network comprising a plurality of
capacitors or open-circuited stubs and one or more electrically
controlled switches or change-over switches, such as
electro-mechanical relays, or microelectromechanical switches, or
PIN diodes or insulated-gate field-effect transistors, used to
cause different capacitors or open-circuited stubs of the network
to contribute to the reactance; or [0011] a network comprising a
plurality of coils or short-circuited stubs and one or more
electrically controlled switches or change-over switches used to
cause different coils or short-circuited stubs of the network to
contribute to the reactance.
[0012] An adjustable impedance device having a reactance which is
adjustable by electrical means may be such that it provides, at a
given frequency, a continuous set of reactance values, this
characteristic being for instance obtained if the adjustable
impedance device is based on the use of a variable capacitance
diode; or a MOS varactor; or a microelectromechanical varactor
(MEMS varactor); or a ferroelectric varactor.
[0013] Many methods exist for automatically adjusting a single
tunable passive antenna, for instance the methods disclosed in the
patent of the U.S. Pat. No. 8,063,839 entitled "Tunable antenna
system", and in the patent of the U.S. Pat. No. 8,325,097 entitled
"Adaptively tunable antennas and method of operation therefore".
Such methods cannot be used for automatically adjusting a plurality
of tunable passive antennas, when the interactions between the
tunable passive antennas are not negligible.
[0014] A method for automatically adjusting a plurality of tunable
passive antennas is disclosed in the patent of the U.S. Pat. No.
8,102,830 entitled "MIMO Radio Communication Apparatus and Method",
in which each tunable passive antenna comprises a main antenna
which is connected to the signal port of said each tunable passive
antenna, and two or more auxiliary antennas. Each of the auxiliary
antennas is connected to an adjustable impedance device, each of
the adjustable impedance devices having a reactance which is
adjustable by electrical means. Each of the tunable passive
antennas may be regarded as a pattern-reconfigurable antenna. This
method is only applicable to a radio receiver using a plurality of
antennas simultaneously for MIMO radio reception.
[0015] A method for automatically adjusting a plurality of tunable
passive antennas is disclosed in the French patent application No.
14/00666 of 20 Mar. 2014, which corresponds to the PCT application
No. PCT/IB2015/051644 of 6 Mar. 2015 (WO 2015/140660). In this
method, a tuning instruction has an effect on each parameter of a
plurality of tunable passive antennas. This method is applicable to
a radio receiver using a plurality of antennas simultaneously and
to a radio transmitter using a plurality of antennas
simultaneously. This method may be used when the interactions
between the tunable passive antennas are not negligible. In
particular, the ninth embodiment of the French patent application
No. 14/00666 and of the PCT application No. PCT/IB2015/051644
discloses a particular implementation of this method, which is
applicable to a radio transmitter connected to m radio ports of an
antenna tuning apparatus coupled to the tunable passive antennas,
where m is an integer greater than or equal to 2. In this
implementation, the tuning instruction is a function of q real
quantities depending on an impedance matrix presented by the radio
ports, where q is an integer greater than or equal to m, these q
real quantities being estimated using m or more different
excitations applied successively to the radio ports. Unfortunately,
this technique is usually not compatible with the specification of
a radio transmitter used for MIMO wireless communication, because
the generation of a sequence of m or more different excitations
entails an emission of electromagnetic waves, which is usually not
compatible with the requirements of all MIMO emission modes of
applicable standards, for instance the LTE-Advanced standards.
[0016] Consequently, there is no known solution to the problem of
automatically adjusting the plurality of tunable passive antennas
coupled to a radio transmitter used for MIMO wireless
communication, in a manner that complies with standards typically
applicable to MIMO wireless networks.
SUMMARY OF THE INVENTION
[0017] The purpose of the invention is a method for automatically
adjusting a plurality of tunable passive antennas, without the
above-mentioned limitations of known techniques, and also an
automatically tunable antenna array using this method.
[0018] In what follows, "having an influence" and "having an
effect" have the same meaning.
[0019] The method of the invention is a method for automatically
adjusting n tunable passive antennas, where n is an integer greater
than or equal to 2, each of the n tunable passive antennas
comprising at least one antenna control device, one or more
characteristics of said each of the n tunable passive antennas
being controlled using said at least one antenna control device,
said at least one antenna control device having at least one
parameter having an influence on said one or more characteristics,
said at least one parameter being adjustable by electrical means,
the method comprising the steps of: [0020] applying excitations to
m user ports, where m is an integer greater than or equal to 2, one
and only one of the excitations being applied to each of the user
ports, the excitations being not applied successively, the m user
ports presenting, at a given frequency, an impedance matrix
referred to as "the impedance matrix presented by the user ports"
and denoted by Z.sub.U; [0021] estimating q real quantities
depending on the impedance matrix presented by the user ports,
where q is an integer greater than or equal to m, using said m
excitations; [0022] using said q real quantities depending on the
impedance matrix presented by the user ports, to obtain "tuning
control signals"; and [0023] applying each of the tuning control
signals to one or more of the antenna control devices, each of said
parameters being mainly determined by one or more of the tuning
control signals.
[0024] In the previous sentence, "each of said parameters" clearly
means "each said at least one parameter of each said at least one
antenna control device of each of the n tunable passive antennas".
According to the invention, the given frequency is for instance a
frequency greater than or equal to 150 kHz. The specialist
understands that the impedance matrix presented by the user ports
is a complex matrix of size m by m.
[0025] Each of the n tunable passive antennas has a port, referred
to as "the signal port of the antenna", comprising two terminals,
which can be used to receive and/or to emit electromagnetic waves.
Each of the n tunable passive antennas comprises at least one
antenna control device, which may comprise one or more other
terminals used for other electrical connections. It is assumed that
each of the n tunable passive antennas behaves, at the given
frequency, with respect to the signal port of the antenna,
substantially as a passive antenna, that is to say as an antenna
which is linear and does not use an amplifier for amplifying
signals received by the antenna or signals emitted by the antenna.
As a consequence of linearity, it is possible to define an
impedance matrix presented by the tunable passive antennas, the
definition of which only considers, for each of the tunable passive
antennas, the signal port of the antenna. This matrix is
consequently of size n x n. Because of the interactions between the
tunable passive antennas, this matrix need not be diagonal. In
particular, the invention may be such that this matrix is not a
diagonal matrix.
[0026] As said above in the prior art section, each of said one or
more characteristics may for instance be an electrical
characteristic such as an impedance at a specified frequency, or an
electromagnetic characteristic such as a directivity pattern at a
specified frequency.
[0027] As shown below in the first embodiment, each of the n
tunable passive antennas may for instance be coupled, directly or
indirectly, to one and only one of the user ports. More precisely,
for each of the n tunable passive antennas, the signal port of the
antenna may for instance be coupled, directly or indirectly, to one
and only one of the user ports. For instance, an indirect coupling
may be a coupling through a feeder and/or through a directional
coupler and/or through a sensing unit. As shown below in the
eleventh embodiment, it is for instance possible that each of the n
tunable passive antennas is coupled, directly or indirectly, to one
or more of the user ports, and that at least one of the n tunable
passive antennas is coupled, directly or indirectly, to two or more
of the user ports. More precisely, it is for instance possible
that: (a) for each of the n tunable passive antennas, the signal
port of the antenna is coupled, directly or indirectly, to one or
more of the user ports; and (b) for at least one of the n tunable
passive antennas, the signal port of the antenna is coupled,
directly or indirectly, to two or more of the user ports.
[0028] One and only one of the excitations is applied to each of
the m user ports, so that there are m excitations applied to the
user ports. These m excitations are not applied successively, that
is to say: them excitations are not applied one after another.
Thus, it is for instance possible that two or more of the
excitations are applied simultaneously. Thus, it is for instance
possible that the m excitations are applied simultaneously.
[0029] According to the invention, each of the excitations may for
instance be a bandpass signal. This type of signal is also
sometimes improperly referred to as "passband signal" or
"narrow-band signal" (in French: "signal a bande etroite"). A
bandpass signal is any real signal s(t), where t denotes the time,
such that the spectrum of s(t) is included in a frequency interval
[f.sub.C-W/2, f.sub.C+W/2], where f.sub.C is a frequency referred
to as "carrier frequency" and where W is a frequency referred to as
"bandwidth", which satisfies W<2f.sub.C. Thus, the Fourier
transform of s(t), denoted by S(f), is non-negligible only in the
frequency intervals [-f.sub.C-W/2, -f.sub.C+W/2] and [f.sub.C-W/2,
f.sub.C+W/2]. The complex envelope of the real signal s(t), also
referred to as "complex baseband equivalent" or
"baseband-equivalent signal", is a complex signal s.sub.B(t) whose
Fourier transform S.sub.B(f) is non-negligible only in the
frequency interval [-W/2, W/2] and satisfies S.sub.B(f)=k
S(f.sub.C+f) in this interval, where k is a real constant which is
chosen equal to the square root of 2 by some authors. The real part
of s.sub.B(t) is referred to as the in-phase component, and the
imaginary part of s.sub.B(t) is referred to as the quadrature
component. The specialist knows that the bandpass signal s(t) may
for instance be obtained: [0030] as the result of a phase and
amplitude modulation of a single carrier at the frequency f.sub.C;
[0031] as a linear combination of a first signal and a second
signal, the first signal being the product of the in-phase
component and a first sinusoidal carrier of frequency f.sub.C, the
second signal being the product of the quadrature component and a
second sinusoidal carrier of frequency f.sub.C, the second
sinusoidal carrier being 90.degree. out of phase with respect to
the first sinusoidal carrier; [0032] in other ways, for instance
without using any carrier, for instance using directly a filtered
output of a digital-to-analog converter.
[0033] The frequency interval [f.sub.C-W/2, f.sub.C-W/2] is a
passband of the bandpass signal. From the definitions, it is clear
that, for a given bandpass signal, several choices of carrier
frequency f.sub.C and of bandwidth W are possible, so that the
passband of the bandpass signal is not uniquely defined. However,
any passband of the bandpass signal must contain any frequency at
which the spectrum of s(t) is not negligible.
[0034] According to the invention, each of the excitations could
for instance be a bandpass signal, the bandpass signal having a
passband which contains said given frequency. In this case, it
would be possible to consider that said given frequency is a
carrier frequency. Thus, in this case, each of the excitations
could for instance be obtained: [0035] as the result of a phase and
amplitude modulation of a single carrier at said given frequency;
[0036] as a linear combination of a first signal and a second
signal, the first signal being the product of the in-phase
component and a first sinusoidal carrier at said given frequency,
the second signal being the product of the quadrature component and
a second sinusoidal carrier at said given frequency; [0037] in
other ways, for instance without using any carrier.
[0038] The complex envelope of the real signal s(t) clearly depends
on the choice of a carrier frequency f.sub.C. However, for a given
carrier frequency, the complex envelope of the real signal s(t) is
uniquely defined, for a given choice of the real constant k.
[0039] According to the invention, for a given choice of the real
constant k, it is possible that, said given frequency being
considered as a carrier frequency, each of the excitations has one
and only one complex envelope, the m complex envelopes of the m
excitations being linearly independent in the set of complex
functions of one real variable, regarded as a vector space over the
field of complex numbers. It was found that this characteristic can
be used in such a way that the effects of each of the excitations
can be identified with suitable signal processing, as if the
excitations had been applied successively to the user ports, so
that, as explained below in the presentation of the first
embodiment, said m excitations can be used to estimate the q real
quantities depending on the impedance matrix presented by the user
ports. The specialist understands that this characteristic of the
method of the invention cannot be obtained with a plurality of
apparatuses for automatically adjusting a single tunable passive
antenna, used for automatically adjusting a plurality of tunable
passive antennas, as presented above in the prior art section. The
specialist also understands that this characteristic of the method
of the invention avoids the interferences which wreak havoc on the
operation of a plurality of apparatuses for automatically adjusting
a single tunable passive antenna, used for automatically adjusting
a plurality of tunable passive antennas, in the case where the
interactions between the tunable passive antennas are not very
small. Moreover, as discussed below in the presentations of the
first and third embodiments, this characteristic is compatible with
the requirements of typical specifications of radio transmitters
used for MIMO wireless communication, because the generation of
excitations having this characteristic is compatible with the
requirements of standards typically applicable to MIMO wireless
networks. For instance, this characteristic is compatible with all
MIMO emission modes of the LTE-Advanced standards. Consequently,
the invention overcomes the above-mentioned limitations of prior
art.
[0040] According to the invention, for a given choice of the real
constant k, it is possible that, said given frequency being
considered as a carrier frequency, each of the excitations has one
and only one complex envelope, the m complex envelopes being
orthogonal to one another for a given scalar product ("scalar
product" is also referred to as "inner product"). The advantage of
this characteristic will be explained below in the presentation of
the second embodiment.
[0041] According to the invention, each of said q real quantities
depending on the impedance matrix presented by the user ports may
for instance be a real quantity representative of the impedance
matrix presented by the user ports.
[0042] According to the invention, each of said q real quantities
depending on the impedance matrix presented by the user ports may
for instance be substantially proportional to the absolute value,
or the phase, or the real part, or the imaginary part of an entry
of the impedance matrix presented by the user ports, or of an entry
of the inverse of the impedance matrix presented by the user ports
(that is, the admittance matrix presented by the user ports), or of
an entry of a matrix of the voltage reflection coefficients at the
user ports, defined as being equal to (Z.sub.U-Z.sub.O)
(Z.sub.U+Z.sub.O).sup.-1, where Z.sub.O is a reference impedance
matrix.
[0043] The specialist understands that the tuning control signals
have an effect on each of said parameters, so that they may have an
influence on the impedance matrix presented by the user ports.
According to the invention, it is possible that the tuning control
signals are such that the impedance matrix presented by the user
ports decreases or minimizes a norm of the image of the impedance
matrix presented by the user ports under a matrix function, the
matrix function being a function from a set of square complex
matrices into the same set of square complex matrices. For
instance, this norm may be a vector norm or a matrix norm. For
instance, if we define a wanted impedance matrix, the wanted
impedance matrix being denoted by Z.sub.W, said matrix function may
be defined by
f(Z.sub.U)=Z.sub.U-Z.sub.W (1)
in which case the image of Z.sub.U under the matrix function is a
difference of impedance matrices, or by
f(Z.sub.U)=Z.sub.U.sup.-1-Z.sub.W.sup.-1 (2)
in which case the image of Z.sub.U under the matrix function is a
difference of admittance matrices, or by
f(Z.sub.U)=(Z.sub.U-Z.sub.W)(Z.sub.U+Z.sub.W).sup.-1 (3)
in which case the image of Z.sub.U under the matrix function is a
matrix of the voltage reflection coefficients at the user ports. We
note that each of these matrix functions is such that f(Z.sub.W) is
a null matrix, so that the norm of f(Z.sub.W) is zero.
[0044] An apparatus implementing the method of the invention is an
automatically tunable antenna array having m "user ports", where m
is an integer greater than or equal to 2, the m user ports
presenting, at a given frequency, an impedance matrix referred to
as "the impedance matrix presented by the user ports" and denoted
by Z.sub.U, the automatically tunable antenna array comprising:
[0045] n tunable passive antennas, where n is an integer greater
than or equal to 2, each of the n tunable passive antennas
comprising at least one antenna control device, one or more
characteristics of said each of the n tunable passive antennas
being controlled using said at least one antenna control device,
said at least one antenna control device having at least one
parameter having an influence on said one or more characteristics,
said at least one parameter being adjustable by electrical means;
[0046] at least m sensing units, each of the sensing units
delivering one or more "sensing unit output signals", each of the
sensing unit output signals being mainly determined by one or more
electrical variables; [0047] a signal processing unit, the signal
processing unit estimating q real quantities depending on the
impedance matrix presented by the user ports, where q is an integer
greater than or equal to m, using the sensing unit output signals
obtained form excitations applied to the user ports, one and only
one of the excitations being applied to each of the user ports, the
m excitations being not applied successively, the signal processing
unit delivering a "tuning instruction" as a function of said q real
quantities depending on the impedance matrix presented by the user
ports; and [0048] a tuning control unit, the tuning control unit
receiving the tuning instruction from the signal processing unit,
the tuning control unit delivering "tuning control signals" to the
tunable passive antennas, the tuning control signals being
determined as a function of the tuning instruction, each of said
parameters being mainly determined by one or more of the tuning
control signals.
[0049] In the previous sentence, "each of said parameters" clearly
means "each said at least one parameter of each said at least one
antenna control device of each of the n tunable passive
antennas".
[0050] The m excitations are not applied successively, that is to
say: the m excitations are not applied one after the other. Thus,
it is for instance possible that two or more of the excitations are
applied simultaneously.
[0051] It is for instance possible that each of the excitations is
a bandpass signal. It is for instance possible that each of these
bandpass signals has a passband which contains said given
frequency.
[0052] For instance, each of said electrical variables may be a
voltage, or an incident voltage, or a reflected voltage, or a
current, or an incident current, or a reflected current. For
instance, each of said electrical variables may be sensed (or
measured) at one of said user ports.
[0053] As explained above, it is for instance possible that each of
the n tunable passive antennas is coupled, directly or indirectly,
to one and only one of the user ports. As explained above, it is
for instance possible that each of the n tunable passive antennas
is coupled, directly or indirectly, to one or more of the user
ports, and that at least one of the n tunable passive antennas is
coupled, directly or indirectly, to two or more of the user
ports.
[0054] The specialist understands that the tunable passive antennas
may be such that the tuning control signals have an effect on the
impedance matrix presented by the user ports, so that a closed-loop
control scheme exists because each of the tuning control signals is
determined as a function of said real quantities depending on the
impedance matrix presented by the user ports. The specialist
understands that the automatically tunable antenna array of the
invention is adaptive in the sense that said parameters are varied
with time as a function of the sensing unit output signals, which
are each mainly determined by one or more electrical variables.
[0055] The specialist understands that, if the tuning control
signals have an effect on the impedance matrix presented by the
user ports, the tuning instruction may for instance be determined
as being a tuning instruction which, among a set of possible tuning
instructions, produces an impedance matrix presented by the user
ports which decreases or minimizes a norm of the image of the
impedance matrix presented by the user ports under a matrix
function, the matrix function being for instance one of the matrix
functions f such that f(Z.sub.U) is given by the equation (1) or
the equation (2) or the equation (3). The specialist also
understands that the tuning instruction may for instance be
determined as being a tuning instruction which provides an
impedance matrix presented by the user ports which is substantially
equal to the wanted impedance matrix, for instance a tuning
instruction such that Z.sub.U=Z.sub.W.
BRIEF DESCRIPTION OF THE DRAWINGS
[0056] Other advantages and characteristics will appear more
clearly from the following description of particular embodiments of
the invention, given by way of non-limiting examples, with
reference to the accompanying drawings in which:
[0057] FIG. 1 shows the block diagram of an automatically tunable
antenna array of the invention, comprising 4 tunable passive
antennas (first embodiment);
[0058] FIG. 2 shows the block diagram of a transmitter for radio
communication using the automatically tunable antenna array shown
in FIG. 1 (first embodiment);
[0059] FIG. 3 shows a first tunable passive antenna, which
comprises a single antenna control device (fourth embodiment);
[0060] FIG. 4 shows a second tunable passive antenna, which
comprises three antenna control devices (fifth embodiment);
[0061] FIG. 5 shows a third tunable passive antenna, which
comprises four antenna control devices (sixth embodiment);
[0062] FIG. 6 shows a fourth tunable passive antenna, which
comprises a single antenna control device (seventh embodiment);
[0063] FIG. 7 shows the block diagram of an automatically tunable
antenna array of the invention, comprising 4 tunable passive
antennas and a multiple-input-port and multiple-output-port
matching network (eighth embodiment);
[0064] FIG. 8 shows the block diagram of a transmitter for radio
communication using the automatically tunable antenna array shown
in FIG. 7 (eighth embodiment);
[0065] FIG. 9 shows the block diagram of an automatically tunable
antenna array of the invention, comprising 4 tunable passive
antennas and a multiple-input-port and multiple-output-port tuning
unit (ninth embodiment);
[0066] FIG. 10 shows the block diagram of a transmitter for radio
communication using the automatically tunable antenna array shown
in FIG. 9 (ninth embodiment);
[0067] FIG. 11 shows the block diagram of an automatically tunable
antenna array of the invention, comprising 4 tunable passive
antennas and a switching unit (thirteenth embodiment);
[0068] FIG. 12 shows the block diagram of a transmitter for radio
communication using the automatically tunable antenna array shown
in FIG. 11 (thirteenth embodiment).
DETAILED DESCRIPTION OF SOME EMBODIMENTS
First Embodiment
[0069] As a first embodiment of a device of the invention, given by
way of non-limiting example, we have represented in FIG. 1 the
block diagram of an automatically tunable antenna array having m=4
user ports (912) (922) (932) (942), the m user ports presenting, at
a given frequency greater than or equal to 30 MHz, an impedance
matrix referred to as "the impedance matrix presented by the user
ports" and denoted by Z.sub.U, the automatically tunable antenna
array comprising: [0070] n=m=4 tunable passive antennas (11) (12)
(13) (14), the n tunable passive antennas operating simultaneously
in a given frequency band, the n tunable passive antennas forming a
multiport antenna array (1), each ofthe tunable passive antennas
comprising at least one antenna control device, one or more
characteristics of said each of the tunable passive antennas being
controlled using said at least one antenna control device, said at
least one antenna control device having at least one parameter
having an effect on said one or more characteristics, said at least
one parameter being adjustable by electrical means; [0071] m
sensing units (91) (92) (93) (94), each of the sensing units
delivering two "sensing unit output signals", each of the sensing
unit output signals being determined by one electrical variable
sensed (or measured) at one of the user ports; [0072] n feeders
(21) (22) (23) (24), each of the feeders having a first end coupled
to a signal port of one and only one of the tunable passive
antennas, each of the feeders having a second end coupled to one
and only one of the user ports, through one and only one of the
sensing units; [0073] a signal processing unit (8), the signal
processing unit estimating q real quantities depending on the
impedance matrix presented by the user ports, where q is an integer
greater than or equal to m, using the sensing unit output signals
obtained for m excitations applied to the user ports, one and only
one of the excitations being applied to each user ports, each of
the excitations being a bandpass signal, the signal processing unit
delivering a "tuning instruction" as a function of said q real
quantities depending on the impedance matrix presented by the user
ports; and [0074] a tuning control unit (4), the tuning control
unit receiving the tuning instruction from the signal processing
unit (8), the tuning control unit delivering "tuning control
signals" to the tunable passive antennas (11) (12) (13) (14), the
tuning control signals being determined as a function of the tuning
instruction, each of said parameters being determined by one or
more of the tuning control signals.
[0075] Each of the sensing units (91) (92) (93) (94) may for
instance be such that the two sensing unit output signals delivered
by said each of the sensing units comprise: a first sensing unit
output signal proportional to a first electrical variable, the
first electrical variable being a voltage across one of the user
ports; and a second sensing unit output signal proportional to a
second electrical variable, the second electrical variable being a
current flowing in said one of the user ports. Said voltage across
one of the user ports may be a complex voltage and said current
flowing in said one of the user ports may be a complex current.
Alternatively, each of the sensing units (91) (92) (93) (94) may
for instance be such that the two sensing unit output signals
delivered by said each of the sensing units comprise: a first
sensing unit output signal proportional to a first electrical
variable, the first electrical variable being an incident voltage
(which may also be referred to as "forward voltage") at one of the
user ports; and a second sensing unit output signal proportional to
a second electrical variable, the second electrical variable being
a reflected voltage at said one of the user ports. Said incident
voltage at one of the user ports may be a complex incident voltage
and said reflected voltage at said one of the user ports may be a
complex reflected voltage.
[0076] Each of the electrical variables is substantially zero if no
excitation is applied to any one of the user ports and if the
tunable passive antennas are not excited by an incident
electromagnetic field.
[0077] The specialist understands that each of the n tunable
passive antennas is coupled, through one of the feeders and one
sensing unit, to one of the user ports. Consequently, each of the n
tunable passive antennas is coupled, indirectly, to one of the user
ports. As shown in FIG. 1, it is possible to consider that each of
the sensing units includes: a first port connected to said second
end of one of the feeders; and a second port which is one of the
user ports.
[0078] An external device has m output ports, each of the output
ports of the external device being coupled to one and only one of
the user ports, each of the user ports being coupled to one and
only one of the output ports of the external device. The external
device is not shown in FIG. 1. The external device applies m
excitations to the user ports, and informs the signal processing
unit (8) of this action. One and only one of said m excitations is
applied to each of the user ports, two or more of the excitations
being applied simultaneously. Each of said m excitations is a
bandpass signal having a passband which contains said given
frequency. Said given frequency being considered as a carrier
frequency, each of the excitations has one and only one complex
envelope (or complex baseband equivalent), the m complex envelopes
being linearly independent in E, where E is the set of complex
functions of one real variable, regarded as a vector space over the
field of complex numbers.
[0079] Let us number the user ports from 1 to m, and let us number
the excitations from 1 to m, in such a way that, if a is an integer
greater than or equal to 1 and less than or equal to m, the
excitation number a is applied to the user port number a. For
instance, if we use t to denote time, the excitations may be such
that, for any integer a greater than or equal to 1 and less than or
equal to m, the excitation number a consists of a current
i.sub.a(t), of complex envelope i.sub.E a(t), applied to the user
port number a, the complex envelopes i.sub.E 1(t), . . . , i.sub.E
m(t) being linearly independent in E. Let us use i.sub.E (t) to
denote the column vector of the complex envelopes i.sub.E 1(t), . .
. , i.sub.E m(t). Let us use u.sub.a(t) to denote the voltage
across the user port number a, and u.sub.Ea(t) to denote the
complex envelope of u.sub.a(t). Let us use u.sub.E (t) to denote
the column vector of the complex envelopes u.sub.E 1(t), . . . ,
u.sub.E m(t). It is possible to show that, if the bandwidth of the
complex envelopes i.sub.E 1(t), . . . , i.sub.E m(t) is
sufficiently narrow, we have
U.sub.E(t)=Z.sub.U i.sub.E(t) (4)
[0080] If we consider the equation (4) for a fixed value of t, then
the entries of u.sub.E(t) and i.sub.E(t) are complex numbers. In
this context, for m.gtoreq.2 it is not possible to solve the
equation (4) to derive Z.sub.U based on the knowledge of u.sub.E
(t) and i.sub.E (t) for a fixed value of t. In contrast, if we
consider the equation (4) where t is a variable, then the entries
of i.sub.E (t) are linearly independent vectors of E. Thus, if we
use S to denote the span of i.sub.E 1(t), . . . , i.sub.E m(t) in
E, we find that i.sub.E 1(t), . . . , i.sub.E m(t) is a basis of S.
In this context, the equation (4) teaches that each entry of
u.sub.E(t) lies in S, and that, for any integer a greater than or
equal to 1 and less than or equal to m, the coordinates of the
vector U.sub.E a(t) in the basis i.sub.E 1(t), . . . , i.sub.E m(t)
are the entries of the row a of Z.sub.U. Since these coordinates
are unique, the equation (4) can be used to derive Z.sub.U based on
the knowledge of (t) and i.sub.E(t), where t is a variable. Thus,
the effects of the different excitations can be identified with
suitable signal processing, as if the different excitations had
been applied successively to the user ports, so that the m
excitations can be used to estimate the impedance matrix presented
by the user ports, and any real quantity depending on the impedance
matrix presented by the user ports. Thus, m excitations which are
not applied successively can be used in the invention, whereas they
cannot be used in the method disclosed in the ninth embodiment of
said French patent application No. 14/00666 and of said PCT
application No. PCT/M2015/051644.
[0081] We have just considered, as an example, the case in which
the excitations are such that, for any integer a greater than or
equal to 1 and less than or equal to m, the excitation number a
consists of a current i.sub.a(t), of complex envelope i.sub.E a(t),
applied to the user port number a, the complex envelopes i.sub.E
1(t), . . . , i.sub.E m (t) being linearly independent in E.
Alternatively, the excitations could for instance be such that, for
any integer a greater than or equal to 1 and less than or equal to
m, the excitation number a consists of a voltage u.sub.a(t), of
complex envelope u.sub.E a(t), applied to the user port number a,
the complex envelopes u.sub.E 1(t), . . . , u.sub.E m(t) being
linearly independent in E. In this case, using a proof similar to
the one presented above for applied currents, we can show that the
effects of the different excitations can be identified with
suitable signal processing, as if the different excitations had
been applied successively to the user ports, so that the m
excitations can be used to estimate the impedance matrix presented
by the user ports, and any real quantity depending on the impedance
matrix presented by the user ports.
[0082] We observe that, in standards typically applicable to MIMO
wireless networks, signals having complex envelopes which are
linearly independent in E are used as reference signals (also
referred to as pilot signals) for MIMO channel estimation. We see
that these signals used as reference signals, if they are applied
to the user ports, can be used as excitations having complex
envelopes which are linearly independent in E. Consequently, this
first embodiment is compatible with the requirements of standards
typically applicable to MIMO wireless networks. This question is
further discussed below, in the third embodiment.
[0083] The specialist understands how the signal processing unit
(8) can use the sensing unit output signals obtained for the m
excitations applied to the user ports, them excitations being
bandpass signals having complex envelopes which are linearly
independent in E, to estimate q real quantities depending on the
impedance matrix presented by the user ports. In this first
embodiment, q=2m.sup.2 and the q real quantities depending on the
impedance matrix presented by the user ports fully determine the
impedance matrix presented by the user ports. For instance, let us
consider the case where the two sensing unit output signals of any
one of said sensing units are proportional to a complex voltage
across one of the user ports and to a complex current flowing in
said one of the user ports, respectively, and where the excitation
number a consists of a current applied to the user port number a,
as explained above. Based on the explanations about the equation
(4), the specialist understands that all entries of Z.sub.U can be
determined once the m excitations have been applied. For instance,
said q real quantities depending on the impedance matrix presented
by the user ports may consist of m.sup.2 real numbers each
proportional to the real part of an entry of Z.sub.U and of m.sup.2
real numbers each proportional to the imaginary part of an entry of
Z.sub.U. For instance, said q real quantities depending on the
impedance matrix presented by the user ports may consist of m.sup.2
real numbers each proportional to the absolute value of an entry of
Z.sub.U and of m.sup.2 real numbers each proportional to the
argument of an entry of Z.sub.U.
[0084] For instance, if the sensing units (91) (92) (93) (94) are
numbered from 1 to m, we may consider the special case in which,
for any integer a greater than or equal to 1 and less than or equal
to m, the sensing unit number a delivers: a first sensing unit
output signal proportional to the voltage u.sub.a(t) across the
user port number a ; and a second sensing unit output signal
proportional to the current i.sub.a(t) flowing in this user port.
In this case, the signal processing unit (8) may for instance
perform an in-phase/quadrature (I/Q) demodulation (homodyne
reception) of all sensing unit output signals, to obtain, for any
integer a greater than or equal to 1 and less than or equal to m,
four analog signals: the real part of u.sub.E a(t); the imaginary
part of u.sub.E a(t); the real part of i.sub.E a(t); and the
imaginary part of i.sub.E a(t). These analog signals may then be
converted into digital signals and further processed in the digital
domain, to estimate said q real quantities depending on the
impedance matrix presented by the user ports, which fully
characterize the impedance matrix presented by the user ports.
[0085] The multiport antenna array (1) is such that each said at
least one parameter of each said at least one antenna control
device of each of the n tunable passive antennas has an effect on
Z.sub.U. Since each of said parameters is determined by one or more
of the tuning control signals, the tuning control signals have an
effect on Z.sub.U. Thus, the tuning instruction has an effect on
Z.sub.U. In this first embodiment, the tuning instruction is such
that the impedance matrix presented by the user ports approximates
a wanted impedance matrix Z.sub.W.
[0086] Since, as explained above, the q real quantities depending
on the impedance matrix presented by the user ports fully determine
Z.sub.U, the signal processing unit determines and delivers a
tuning instruction such that the resulting tuning control signals
produce a Z.sub.U such that a norm of Z.sub.U-Z.sub.W is
sufficiently small. The specialist understands how the tuning
instruction can be determined. The operation of the signal
processing unit is such that a tuning instruction is generated at
the end of a tuning sequence, and is valid until a next tuning
instruction is generated at the end of a next tuning sequence.
[0087] The external device also delivers "instructions of the
external device" to the signal processing unit (8), said
instructions of the external device informing the signal processing
unit that said excitations have been applied, or are being applied,
or will be applied. For instance, the external device may initiate
a tuning sequence when it informs the signal processing unit that
it will apply the excitations to the user ports. For instance, the
signal processing unit may end the tuning sequence when, after the
excitations have been applied, a tuning instruction has been
delivered. Additionally, the external device provides other signals
to the signal processing unit, and/or receives other signals from
the signal processing unit. The electrical links needed to deliver
said instructions of the external device and to carry such other
signals are not shown in FIG. 1.
[0088] The tuning instruction may be of any type of digital
message. In this first embodiment, an adaptive process is carried
out by the signal processing unit, during each tuning sequence. The
adaptive process is the following: during each tuning sequence, the
signal processing unit estimates the q real quantities depending on
the impedance matrix presented by the user ports, and uses an
algorithm to determine a tuning instruction such that the impedance
matrix presented by the user ports approximates Z.sub.U. The
algorithm is based on the frequency of operation and on the q real
quantities depending on the impedance matrix presented by the user
ports, and it takes into account the tuning instruction which was
applicable while the sensing units delivered the sensing unit
output signals used to estimate the q real quantities depending on
the impedance matrix presented by the user ports.
[0089] If the tuning control unit (4) was not present, the tuning
instruction would have no effect on Z.sub.U. The specialist
understands that, in this case, Z.sub.U would depend on the
frequency of operation and on the electromagnetic characteristics
of the volume surrounding the antennas. In particular, if the
multiport antenna array (1) was built in a portable transceiver,
for instance a user equipment (UE) of an LTE wireless network,
Z.sub.U would depend on the position of the body of the user, a
phenomenon referred to as "user interaction". The specialist
understands that the automatically tunable antenna array shown in
FIG. 1 may be used to automatically reduce or cancel any variation
in Z.sub.U caused by a variation in the frequency of operation,
and/or caused by the user interaction.
[0090] In this first embodiment, n=m=4. Thus, it is possible that n
is greater than or equal to 3, it is possible that n is greater
than or equal to 4, it is possible that m is greater than or equal
to 3, and it is possible that m is greater than or equal to 4.
[0091] As an example, FIG. 2 shows the block diagram of a
transmitter for radio communication (or a transceiver for radio
communication) using the automatically tunable antenna array shown
in FIG. 1. The transmitter for radio communication (or transceiver
for radio communication) shown in FIG. 2 comprises: [0092] the
tunable passive antennas (11) (12) (13) (14) forming a multiport
antenna array (1) of FIG. 1; [0093] the sensing units (91) (92)
(93) (94) of FIG. 1; [0094] the feeders (21) (22) (23) (24) of FIG.
1; [0095] the signal processing unit (8) of FIG. 1; [0096] the
tuning control unit (4) of FIG. 1; and [0097] a radio device (5)
which consists of all parts of the transmitter (or transceiver)
which are not shown elsewhere in FIG. 2, the radio device having
m=4 radio ports, the radio device delivering "tuning sequence
instructions" which indicate when a tuning sequence is being
performed, m excitations being delivered by the radio ports during
said tuning sequence, one and only one of the excitations being
delivered by each of the radio ports.
[0098] In FIG. 2, each of the feeders has a first end coupled to a
signal port of one and only one of the tunable passive antennas,
and each of the feeders has a second end coupled to one and only
one of the radio ports, through one and only one of the sensing
units. The m radio ports see, at the given frequency, an impedance
matrix referred to as "the impedance matrix seen by the radio
ports", which clearly may be considered as being the impedance
matrix presented by the user ports and denoted by Z.sub.U.
[0099] The radio device (5) performs functions which were, in the
explanations provided above about FIG. 1, assigned to the external
device. The tuning sequence instructions are delivered to the
signal processing unit (8). They perform functions which were, in
the explanations provided above about FIG. 1, assigned to the
instructions of the external device. Additionally, the radio device
provides other signals to the signal processing unit, and/or
receives other signals from the signal processing unit.
[0100] The signal processing unit (8) also estimates one or more
quantities each depending on the power delivered by the radio
ports. Information on said quantities each depending on the power
delivered by the output ports is sent to the radio device (5), in
which it may be used for radiated power control when the
transmitter (or transceiver) transmits.
[0101] The transmitter (or transceiver) is used for MIMO wireless
transmission in a cellular network. The excitations have complex
envelopes which are compatible with the requirements of standards
typically applicable to MIMO wireless networks.
[0102] In the automatically tunable antenna array, automatic
adjustment of the parameters of the antenna control devices are
used to reduce or cancel any variation in Z.sub.U caused by a
variation in the frequency of operation, and/or caused by the user
interaction. Consequently, this first embodiment provides a
solution to the problem of automatically adjusting the plurality of
tunable passive antennas coupled to a radio transmitter used for
MIMO wireless communication, in a manner that complies with
standards typically applicable to MIMO wireless networks.
Second Embodiment
[0103] The second embodiment of a device of the invention, given by
way of non-limiting example, also corresponds to the automatically
tunable antenna array having m=4 user ports (912) (922) (932) (942)
shown in FIG. 1, and all explanations provided for the first
embodiment are applicable to this second embodiment. Additionally,
in this second embodiment, the complex envelopes of the m
excitations are orthogonal to each other. More precisely, the
complex envelopes of the m excitations are orthogonal to one
another, for a given scalar product. Moreover, the scalar product
of any one of the m complex envelopes and itself is nonzero, so
that the orthogonality requirements entail that the m complex
envelopes are linearly independent. We may use <f|g> to
denote the scalar product of two functions f and g, which may be
any scalar product satisfying the properties of conjugate symmetry,
linearity in the second argument, and positivity (we do not require
positive definiteness). For instance, we may consider that each of
said complex envelope is square-integrable, and that the scalar
product is the usual scalar product of the Hilbert space of
square-integrable functions of a real variable, which, for two
square-integrable functions f and g, is given by
f | g = .intg. - .infin. .infin. f ( x ) _ g ( x ) dx ( 5 )
##EQU00001##
in which the bar above f(x) denotes the complex conjugate.
Alternatively, we may for instance consider that two functions f
and g are sampled at the same points in time, to obtain the samples
f[j] off and the samples g[j] of g, where j is an integer, and that
the scalar product is the usual scalar product of finite energy
sequences, which is given by
f | g = j = - .infin. .infin. f [ j ] _ g [ j ] ( 6 )
##EQU00002##
[0104] Let us for instance consider the case in which the
excitations are such that, for any integer a greater than or equal
to 1 and less than or equal to m, the excitation number a consists
of a current i.sub.a(t), of complex envelope i.sub.E a(t), applied
to the user port number a, the complex envelopes i.sub.E 1(t), . .
. , i.sub.E m(t) being orthogonal to each other. In this case, the
equation (4) is applicable, and the coordinates of the vector
u.sub.E a(t) in the basis i.sub.E 1(t), . . . , i.sub.E m(t) of S
can be easily computed, since, for any integer b greater than or
equal to 1 and less than or equal to m, the b-th coordinate of the
vector u.sub.E a(t) in the basis i.sub.E 1(t), . . . , i.sub.E
m(t), denoted by z.sub.a b is clearly given by
z ab = i Eb | u Ea i Eb | i Eb ( 7 ) ##EQU00003##
[0105] Moreover, in this case, the coordinates of the vector
u.sub.E a(t) in the basis i.sub.E 1(t), . . . , i.sub.E m(t) being
the entries of the row a of Z.sub.U, we find that z.sub.a b is the
entry of the row a and the column b of Z.sub.U. Thus, the equation
(7) can be used to derive Z.sub.U based on the knowledge of
u.sub.E(t) and i.sub.E(t), where t is a variable. Thus, the effects
of the different excitations can be identified with suitable signal
processing, as if the different excitations had been applied
successively to the user ports, so that the m excitations can be
used to estimate the impedance matrix presented by the user ports,
and any real quantity depending on the impedance matrix presented
by the user ports.
[0106] We have just considered, as an example, the case in which
the excitations are such that, for any integer a greater than or
equal to 1 and less than or equal to m, the excitation number a
consists of a current i.sub.a(t), of complex envelope i.sub.E a(t),
applied to the user port number a, the complex envelopes
i.sub.E1(t), . . . , i.sub.Em(t) being orthogonal to each other.
Alternatively, the excitations could for instance be such that, for
any integer a greater than or equal to 1 and less than or equal to
m, the excitation number a consists of a voltage u.sub.a(t), of
complex envelope u.sub.E a(t), applied to the user port number a,
the complex envelopes u.sub.E 1(t), . . . , u.sub.E m(t) being
orthogonal to each other. In this case, using a proof similar to
the one presented above for applied currents, we can show that the
effects of the different excitations can be identified with
suitable signal processing, as if the different excitations had
been applied successively to the user ports, so that the m
excitations can be used to estimate the impedance matrix presented
by the user ports, and any real quantity depending on the impedance
matrix presented by the user ports.
[0107] The specialist understands how to generate m excitations
having complex envelopes which are orthogonal to one another. For
instance, let us consider m arbitrary sequences of data symbols,
each sequence being modulated on a single sub-carrier of an
orthogonal frequency division multiplexing (OFDM) signal, different
sequences being modulated on different sub-carriers. These m
modulated sub-carriers are orthogonal to one another, so that each
of these modulated sub-carriers could be used as the complex
envelope of one of them excitations. For instance, orthogonality
also exists between any two different resource elements of an OFDM
signal (a resource element means one OFDM sub-carrier for the
duration of one OFDM symbol), so that m different resource elements
could each be used to obtain the complex envelope of one of them
excitations.
[0108] The specialist understands how the signal processing unit
(8) can use the sensing unit output signals obtained for them
excitations applied to the user ports, them excitations being
bandpass signals having complex envelopes which are orthogonal to
one another, to estimate q real quantities depending on the
impedance matrix presented by the user ports. For instance, let us
consider the case where the two sensing unit output signals of any
one of said sensing units are proportional to a complex voltage
across one of the user ports and to a complex current flowing in
said one of the user ports, respectively, and where the excitation
number a consists of a current applied to the user port number a.
Based on the explanations about the equation (7), the specialist
understands that all entries of Z.sub.U can be determined once the
m different excitations have been applied.
[0109] For instance, if the sensing units (91) (92) (93) (94) are
numbered from 1 to m, we may consider the special case in which,
for any integer a greater than or equal to 1 and less than or equal
to m, the sensing unit number a delivers: a first sensing unit
output signal proportional to the voltage u.sub.a(t) across the
user port number a; and a second sensing unit output signal
proportional to the current i.sub.a(t) flowing in the user port
number a. In this case, the signal processing unit (8) may for
instance perform a down-conversion of all sensing unit output
signals, followed by an in-phase/quadrature (I/Q) demodulation
(heterodyne reception), to obtain, for any integer a greater than
or equal to 1 and less than or equal to m, four analog signals: the
real part of u.sub.E a(t); the imaginary part of u.sub.E a(t); the
real part of i.sub.E a(t); and the imaginary part of i.sub.E a(t).
These analog signals may then be converted into digital signals and
further processed in the digital domain, based on equation (6) and
on equation (7) as explained above, to estimate said q real
quantities depending on the impedance matrix presented by the user
ports, which fully characterize the impedance matrix presented by
the user ports.
Third Embodiment
Best Mode
[0110] The third embodiment of a device of the invention, given by
way of non-limiting example and best mode of carrying out the
invention, also corresponds to the automatically tunable antenna
array having m=4 user ports (912) (922) (932) (942) shown in FIG.
1, and all explanations provided for the first embodiment are
applicable to this third embodiment. Additionally, in this third
embodiment, each of the complex envelopes of the m excitations is
the sum of a first complex signal and a second complex signal, the
first complex signal being referred to as the primary component of
the complex envelope, the second complex signal being referred to
as the secondary component of the complex envelope, the primary
components of the m complex envelopes being orthogonal to each
other, each of the primary components of the m complex envelopes
being orthogonal to each of the secondary components of the m
complex envelopes. More precisely, the primary components of the m
complex envelopes are orthogonal to one another, for a given scalar
product, and each of the primary components of the m complex
envelopes is orthogonal to each of the secondary components of the
m complex envelopes, for the given scalar product. Moreover, the
scalar product of any one of the primary components of the m
complex envelopes and itself is nonzero, so that the orthogonality
requirements entail that the m complex envelopes are linearly
independent.
[0111] Let us for instance consider the case in which the
excitations are such that, for any integer a greater than or equal
to l and less than or equal to m, the excitation number a consists
of a current i.sub.a(t), of complex envelope i.sub.E a(t), applied
to the user port number a, the complex envelope i.sub.E a(t) being
of the form
i.sub.E a(t)=i.sub.C a(t)+i.sub.D a(t) (8)
where i.sub.C a (t) is the primary component of the complex
envelope, and i.sub.D a (t) is the secondary component of the
complex envelope, the primary components i.sub.C 1(t), . . . ,
t.sub.Cm(t) of them complex envelopes being orthogonal to each
other, and each of the primary components i.sub.C 1(t), . . . ,
i.sub.C m(t) of the m complex envelopes being orthogonal to each of
the secondary components i.sub.D 1(t), . . . , i.sub.D m(t) of the
m complex envelopes. In this case, the equation (4) is applicable,
and the coordinates of the vector u.sub.E a(t) in the basis
i.sub.E1(t), . . . , i.sub.E m(t) of S can be easily computed,
since, for any integer b greater than or equal to 1 and less than
or equal to m, the b-th coordinate of the vector u.sub.E a(t) in
the basis i.sub.E 1(t), . . . , i.sub.E m(t), denoted by z.sub.a b,
is clearly given by
z ab = i Cb | u Ea i Cb | i Cb ( 9 ) ##EQU00004##
[0112] Moreover, in this case, the coordinates of the vector
u.sub.E a(t) in the basis i.sub.E 1(t), . . . , i.sub.E m(t) being
the entries of the row a of Z.sub.U, we find that z.sub.a b is the
entry of the row a and the column b of Z.sub.U. Thus, the equation
(9) can be used to derive Z.sub.U based on the knowledge of
u.sub.E(t) and i.sub.C 1(t), . . . , i.sub.C m(t), where t is a
variable. Thus, the effects of the different excitations can be
identified with suitable signal processing, as if the different
excitations had been applied successively to the user ports, so
that the m excitations can be used to estimate the impedance matrix
presented by the user ports, and any real quantity depending on the
impedance matrix presented by the user ports.
[0113] We have just considered, as an example, the case in which
the excitations are such that, for any integer a greater than or
equal to 1 and less than or equal to m, the excitation number a
consists of a current i.sub.a(t), of complex envelope i.sub.E a(t),
applied to the user port number a, the complex envelope i.sub.E
a(t) being the sum of i.sub.C a(t) and i.sub.D a (t), where i.sub.C
a(t) is the primary component of the complex envelope, and i.sub.D
a(t) is the secondary component of the complex envelope, the
primary components i.sub.C1(t), . . . , i.sub.Cm(t) of the m
complex envelopes being orthogonal to each other, each of the
primary components i.sub.C1(t), . . . , i.sub.Cm(t) of the m
complex envelopes being orthogonal to each of the secondary
components i.sub.D1(t), . . . , i.sub.Dm(t) of the m complex
envelopes. Alternatively, the excitations could for instance be
such that, for any integer a greater than or equal to 1 and less
than or equal to m, the excitation number a consists of a voltage
u.sub.a(t), of complex envelope u.sub.E a(t), applied to the user
port number a, the complex envelope u.sub.E a(t) being the sum of
u.sub.C a(t) and u.sub.D a(t), where u.sub.C a(t) is the primary
component of the complex envelope, and u.sub.D a(t) is the
secondary component of the complex envelope, the primary components
u.sub.C1(t), . . . , u.sub.Cm(t) of them complex envelopes being
orthogonal to each other, each of the primary components u.sub.C
1(t), . . . , u.sub.C m(t) of the m complex envelopes being
orthogonal to each of the secondary components u.sub.D1(t), . . . ,
u.sub.Dm(t) of the m complex envelopes. In this case, using a proof
similar to the one presented above for applied currents, we can
show that the effects of the different excitations can be
identified with suitable signal processing, as if the different
excitations had been applied successively to the user ports, so
that the m excitations can be used to estimate the impedance matrix
presented by the user ports, and any real quantity depending on the
impedance matrix presented by the user ports.
[0114] We observe that the type of excitations used in the second
embodiment is a special case of the more general type of
excitations used in this third embodiment, since excitations used
in this third embodiment and having zero secondary components can
be used in the second embodiment.
[0115] The specialist understands how to generate m excitations
having complex envelopes, each of said complex envelopes being the
sum of a first complex signal and a second complex signal, the
first complex signal being referred to as the primary component of
the complex envelope, the second complex signal being referred to
as the secondary component of the complex envelope, the primary
components of the m complex envelopes being orthogonal to each
other, each of the primary components of the m complex envelopes
being orthogonal to each of the secondary components of the m
complex envelopes. For instance, let us consider m arbitrary
sequences of data symbols, each sequence being modulated on a
single sub-carrier of an OFDM signal, different sequences being
modulated on different sub-carriers. The sub-carriers modulated by
the m arbitrary sequences are orthogonal to one another, and each
of them is orthogonal to any combination of sub-carriers which are
not modulated by any one of the m arbitrary sequences, and which
may carry any data. Thus, each of the sub-carriers modulated by the
m arbitrary sequences could be used as the primary component of the
complex envelope of one of the m excitations, and any combination
of sub-carriers which are not modulated by any one of the m
arbitrary sequences, and which may carry any data, could be used as
the secondary component of the complex envelope of any one of them
excitations. For instance, let us consider m different resource
elements of an OFDM signal. The m different resource elements are
orthogonal to one another, and each of the m different resource
elements is orthogonal to any combination of resource elements
which are not one of said m different resource elements. Thus, each
of said m different resource elements could be used to obtain the
primary component of the complex envelope of one of them
excitations, and any combination of resource elements which are not
one of said m different resource elements could be used to obtain
the secondary component of the complex envelope of any one of the m
excitations.
[0116] We observe that, in typical standards applicable to MIMO
wireless networks, OFDM or single carrier frequency domain
equalization (SC-FDE) is used for transmission, and different
resource elements in different spatial layers (also referred to as
"spatial streams") are used to provide reference signals (also
referred to as "pilots") for MIMO channel estimation. Such a
reference signal, considered in a given spatial layer, can be used
as the primary component of the complex envelope of one of the m
excitations, and any combination of resource elements which are not
used by such a reference signal, considered in a given spatial
layer and carrying any data symbols, can be used to obtain the
secondary component of the complex envelope of any one of the m
excitations. This is because the reference signals meet suitable
orthogonality relations. Consequently, this third embodiment is
compatible with the requirements of standards typically applicable
to MIMO wireless networks.
[0117] The specialist understands how the signal processing unit
(8) can use the sensing unit output signals obtained for them
excitations applied to the user ports, them excitations being
bandpass signals having complex envelopes which are the sum of a
first complex signal and a second complex signal meeting the
requirements of this third embodiment, to estimate q real
quantities depending on the impedance matrix presented by the user
ports. For instance, let us consider the case where the two sensing
unit output signals of any one of said sensing units are
proportional to a complex voltage across one of the user ports and
to a complex current flowing in said one of the user ports,
respectively, and where, for any integer a greater than or equal to
1 and less than or equal tom, the excitation number a consists of a
current applied to the user port number a. Based on the
explanations about the equation (9), the specialist understands
that all entries of Z.sub.U can be determined once the m different
excitations have been applied.
[0118] For instance, if the sensing units (91) (92) (93) (94) are
numbered from 1 to m, we may consider the special case in which,
for any integer a greater than or equal to 1 and less than or equal
to m, the sensing unit number a delivers: a first sensing unit
output signal proportional to the voltage u.sub.a(t) across the
user port number a ; and a second sensing unit output signal
proportional to the current i.sub.a(t) flowing in the user port
number a. In this case, the signal processing unit (8) may for
instance perform a down-conversion of all sensing unit output
signals, followed by a conversion into digital signals using
bandpass sampling, and by a digital quadrature demodulation, to
obtain, for any integer a greater than or equal to 1 and less than
or equal to m, four digital signals: the samples of the real part
of u.sub.E a(t); the samples of the imaginary part of u.sub.E a(t);
the samples of the real part of i.sub.E a(t); and the samples of
the imaginary part of i.sub.E a(t). OFDM demodulation may for
instance be used to obtain, for any integer a greater than or equal
to 1 and less than or equal to m, the samples of the real part of
i.sub.C a(t) and the samples of the imaginary part of i.sub.C a(t).
These digital signals may then be further processed, based on
equation (6) and on equation (9) as explained above, to estimate
said q real quantities depending on the impedance matrix presented
by the user ports, which fully characterize the impedance matrix
presented by the user ports.
Fourth Embodiment
[0119] The fourth embodiment of a device of the invention, given by
way of non-limiting example, also corresponds to the automatically
tunable antenna array having m=4 user ports shown in FIG. 1, and
all explanations provided for the first embodiment are applicable
to this fourth embodiment.
[0120] A tunable passive antenna (11) used in this fourth
embodiment is shown in FIG. 3. The other tunable passive antennas
(12) (13) (14) used in this fourth embodiment may be identical to
the tunable passive antenna shown in FIG. 3. The tunable passive
antenna shown in FIG. 3 comprises a planar metallic structure (111)
built above a ground plane (115), a feeder connection point (116)
where an unbalanced feeder is connected to the metallic structure,
and an antenna control device (112). The metallic structure is
slotted and such that, if the antenna control device was not
present, the tunable passive antenna would be an example of a
planar inverted-F antenna, also referred to as PIFA. The antenna
control device is a MEMS switch comprising a first terminal (113)
connected to the metallic structure (111) at a first side of the
slot, and a second terminal (114) connected to the metallic
structure (111) at a second side of the slot. The specialist
understands that the self-impedance of the tunable passive antenna,
in a given test configuration and at a given frequency, is a
characteristic of the tunable passive antenna which may be varied
using said antenna control device, so that this characteristic is
controlled using said antenna control device. The state of the MEMS
switch (on or off) is a parameter of the antenna control device
which has an influence on said characteristic. This parameter of
the antenna control device is adjustable by electrical means, but
the circuits and the control links needed to determine the state of
the antenna control device are not shown in FIG. 3.
Fifth Embodiment
[0121] The fifth embodiment of an apparatus of the invention, given
by way of non-limiting example, also corresponds to the
automatically tunable antenna array having m=4 user ports shown in
FIG. 1, and all explanations provided for the first embodiment are
applicable to this fifth embodiment.
[0122] A tunable passive antenna (11) used in this fifth embodiment
is shown in FIG. 4. The other tunable passive antennas (12) (13)
(14) used in this fifth embodiment may be identical to the tunable
passive antenna shown in FIG. 3 or to the tunable passive antenna
shown in FIG. 4. The tunable passive antenna shown in FIG. 4
comprises a planar metallic structure (111) built above a ground
plane (115), a feeder connection point (116) where an unbalanced
feeder is connected to a metallic strip (117) lying between the
ground plane and the metallic structure, and three antenna control
devices (112). Each of the antenna control devices is an adjustable
impedance device having a reactance at a given frequency,
comprising a first terminal (113) connected to the metallic
structure (111), and a second terminal (114) connected to the
ground plane (115). The specialist understands that the
self-impedance of the tunable passive antenna, in a given test
configuration and at the given frequency, is a characteristic of
the tunable passive antenna which may be varied using said antenna
control devices, so that this characteristic is controlled using
said antenna control devices. Each of the antenna control devices
has a reactance at the given frequency, this reactance being a
parameter of said each of the antenna control devices, this
parameter having an influence on said characteristic. This
parameter of each of the antenna control devices is adjustable by
electrical means, but the circuits and the control links needed to
determine the reactance of each of the antenna control devices are
not shown in FIG. 4.
Sixth Embodiment
[0123] The sixth embodiment of an apparatus of the invention, given
by way of non-limiting example, also corresponds to the
automatically tunable antenna array having m=4 user ports shown in
FIG. 1, and all explanations provided for the first embodiment are
applicable to this sixth embodiment.
[0124] A tunable passive antenna (11) used in this sixth embodiment
is shown in FIG. 5. The other tunable passive antennas (12) (13)
(14) used in this sixth embodiment may be identical to the tunable
passive antenna shown in FIG. 3, or to the tunable passive antenna
shown in FIG. 4, or to the tunable passive antenna shown in FIG. 5.
The tunable passive antenna (11) shown in FIG. 5 has a plane of
symmetry orthogonal to the drawing. Thus, the tunable passive
antenna has a first half-antenna, on the left in FIG. 5, and a
second half-antenna, on the right in FIG. 5. The tunable passive
antenna comprises a first terminal (118) where a first conductor of
a balanced feeder is connected to the first half-antenna, and a
second terminal (119) where a second conductor of the balanced
feeder is connected to the second half-antenna. Each half-antenna
includes three segments and two antenna control devices (112). Each
of the antenna control devices is an adjustable impedance device
having a reactance at a given frequency, comprising a first
terminal connected to a segment of an half-antenna, and a second
terminal connected to another segment of this half-antenna. The
specialist understands that the self-impedance of the tunable
passive antenna, in a given test configuration and at the given
frequency, is a characteristic of the tunable passive antenna which
may be varied using said antenna control devices, so that this
characteristic is controlled using said antenna control devices.
Each of the antenna control devices has a reactance at the given
frequency, this reactance being a parameter of said each of the
antenna control devices, this parameter having an influence on said
characteristic. This parameter of each of the antenna control
devices is adjustable by electrical means, but the circuits and the
control links needed to determine the reactance of each of the
antenna control devices are not shown in FIG. 5.
Seventh Embodiment
[0125] The seventh embodiment of an apparatus of the invention,
given by way of non-limiting example, also corresponds to the
automatically tunable antenna array having m=4 user ports shown in
FIG. 1, and all explanations provided for the first embodiment are
applicable to this seventh embodiment.
[0126] A tunable passive antenna (12) used in this seventh
embodiment is shown in FIG. 6. The other tunable passive antennas
(11) (13) (14) used in this seventh embodiment may be identical to
the tunable passive antenna shown in FIG. 6. The tunable passive
antenna (12) shown in FIG. 6 comprises a main antenna (121), a
parasitic antenna (122), a feeder connection point (127) where an
unbalanced feeder (128) is connected to the main antenna and to
ground (126), and an antenna control device (123). The antenna
control device is an adjustable impedance device having a reactance
at a given frequency, comprising a first terminal (124) connected
to the parasitic antenna (122), and a second terminal (125)
connected to ground (126). The specialist understands that the
directivity pattern of the tunable passive antenna (12), in a given
test configuration and at the given frequency, is a characteristic
of the tunable passive antenna which may be varied using said
antenna control device, so that this characteristic is controlled
using said antenna control device. The reactance of the antenna
control device at the given frequency is a parameter of said
antenna control device which has an influence on said
characteristic. This parameter of the antenna control device is
adjustable by electrical means, but the circuits and the control
links needed to determine the reactance of the antenna control
device are not shown in FIG. 6.
[0127] However, the specialist understands that this parameter also
has an influence on the self-impedance of the tunable passive
antenna, so that the self-impedance of the tunable passive antenna,
in a given test configuration and at the given frequency, is also a
characteristic of the tunable passive antenna which may be varied
using said antenna control device. The tunable passive antenna (12)
could also comprise other parasitic antennas each coupled to an
antenna control device.
Eighth Embodiment
[0128] As an eighth embodiment of a device of the invention, given
by way of non-limiting example, we have represented in FIG. 7 the
block diagram of an automatically tunable antenna array having m=4
user ports (912) (922) (932) (942), the m user ports presenting, at
a given frequency greater than or equal to 300 MHz, an impedance
matrix referred to as "the impedance matrix presented by the user
ports" and denoted by Z.sub.U, the automatically tunable antenna
array comprising: [0129] n=4 tunable passive antennas (11) (12)
(13) (14), then tunable passive antennas operating simultaneously
in a given frequency band, the n tunable passive antennas forming a
multiport antenna array (1), each of the tunable passive antennas
comprising at least one antenna control device, said at least one
antenna control device having at least one parameter having an
effect on one or more characteristics of said each of the tunable
passive antennas, said at least one parameter being adjustable by
electrical means; [0130] m sensing units (91) (92) (93) (94), each
of the sensing units delivering two "sensing unit output signals",
each of the sensing unit output signals being determined by one
electrical variable measured at one of the user ports; [0131] a
multiple-input-port and multiple-output-port network (3) having m
input ports and n output ports, each of the m input ports being
coupled to one and only one of the user ports, through one and only
one of the sensing units; [0132] n feeders (21) (22) (23) (24),
each of the feeders having a first end coupled to a signal port of
one and only one of the tunable passive antennas, each of the
feeders having a second end coupled to one and only one of the n
output ports; [0133] a signal processing unit (8), the signal
processing unit estimating q real quantities depending on the
impedance matrix presented by the user ports, where q is an integer
greater than or equal to m, using the sensing unit output signals
obtained for m excitations applied by an external device to the
user ports (the external device is not shown in FIG. 7), one and
only one of the excitations being applied to each user ports, the
excitations being not applied successively, the signal processing
unit delivering a "tuning instruction" as a function of said q real
quantities depending on the impedance matrix presented by the user
ports; and [0134] a tuning control unit (4), the tuning control
unit receiving the tuning instruction from the signal processing
unit (8), the tuning control unit delivering "tuning control
signals" to the tunable passive antennas (11) (12) (13) (14), the
tuning control signals being determined as a function of the tuning
instruction, each of said parameters being mainly determined by one
or more of the tuning control signals.
[0135] The multiple-input-port and multiple-output-port network (3)
is a circuit which behaves, at the given frequency, with respect to
its input ports and output ports, substantially as a passive linear
device, where "passive" is used in the meaning of circuit theory.
More precisely, the multiple-input-port and multiple-output-port
network behaves, at the given frequency, with respect to the n
output ports and the m input ports, substantially as a passive
linear (n+m)-port device. As a consequence of linearity, it is
possible to define the impedance matrix presented by the input
ports. As a consequence of passivity, the multiple-input-port and
multiple-output-port network does not provide amplification.
[0136] The multiple-input-port and multiple-output-port network (3)
allows, at the given frequency, transfers of power from its input
ports to its output ports and from its output ports to its input
ports, these transfers of power being ideally lossless, or nearly
lossless. A suitable multiple-input-port and multiple-output-port
network may be such that it is not composed of a plurality of
independent and uncoupled single-input-port and single-output-port
networks. Conversely, in the case n=m, a suitable
multiple-input-port and multiple-output-port network may be such
that it is composed of m independent and uncoupled
single-input-port and single-output-port networks.
[0137] The multiple-input-port and multiple-output-port network is
such that, at the given frequency, an impedance matrix presented by
the input ports (the sensing units are such that this impedance
matrix is close to Z.sub.U) is different from an impedance matrix
seen by the output ports. Thus, the multiple-input-port and
multiple-output-port network contributes to the design goal of this
eighth embodiment: being able to obtain, at any frequency in a
specified frequency interval, a tuning instruction such that an
impedance matrix presented by the user ports approximates a wanted
impedance matrix Z.sub.W, the wanted impedance matrix being a
diagonal matrix. For this reason, the multiple-input-port and
multiple-output-port network may be regarded as a matching network,
or as a matching and decoupling network, and it may for instance be
referred to as "multiple-input-port and multiple-output-port
matching network".
[0138] The specialist understands that each of the n tunable
passive antennas is coupled, through one of the feeders, the
multiple-input-port and multiple-output-port network and one or
more sensing units, to one or more of the user ports. Consequently,
each of the n tunable passive antennas is coupled, indirectly, to
one or more of the user ports. As shown in FIG. 7, it is possible
to consider that each of the sensing units includes: a first port
connected to one of said input ports; and a second port which is
one of the user ports.
[0139] The tuning instruction may be of any type of digital
message. In this eighth embodiment, an adaptive process is carried
out by the signal processing unit, during one or more tuning
sequences. The adaptive process is the following: during each of
said tuning sequences, the signal processing unit estimates the q
real quantities depending on the impedance matrix presented by the
user ports, and uses a lookup table (also spelled "look-up table")
to determine the tuning instruction, based on the frequency of
operation, on the q real quantities depending on the impedance
matrix presented by the user ports, and on the tuning instruction
which was applicable while the sensing units were delivering the
sensing unit output signals used to estimate the q real quantities
depending on the impedance matrix presented by the user ports. The
specialist understands how to build and use such a lookup table.
The lookup table is such that the adjustment of the tunable passive
antennas is always optimal or almost optimal.
[0140] In this eighth embodiment, each of the antenna control
devices is an adjustable impedance device providing an adjustable
reactance. The reactance of an adjustable impedance device may
depend on the ambient temperature, for some types of adjustable
impedance devices. If such a type of adjustable impedance device is
used in the tunable passive antennas, it is possible that the
tuning control signals are determined as a function of the tuning
instruction and as a function of one or more temperatures, to
compensate the effect of temperature on the reactance of each of
the adjustable impedance devices of the tunable passive antennas.
If such a type of adjustable impedance device is used in the
tunable passive antennas, it is also possible that one or more
temperatures are taken into account to obtain the tuning
instruction, to compensate the effect of temperature on the
reactance of each of the adjustable impedance devices of the
tunable passive antennas. In this case, the signal processing unit
delivers a tuning instruction as a function of said q real
quantities depending on the impedance matrix presented by the user
ports, and as a function of said one or more temperatures.
[0141] In order to respond to variations in the electromagnetic
characteristics of the volume surrounding the antennas and/or in
said one or more temperatures, the tuning instruction may be
generated repeatedly. For instance, a new tuning sequence ending
with the delivery of a new tuning instruction may start
periodically, for instance every 10 milliseconds.
[0142] As an example, FIG. 8 shows the block diagram of a
transmitter for radio communication (or of a transceiver for radio
communication) using the automatically tunable antenna array shown
in FIG. 7. The transmitter for radio communication (or transceiver
for radio communication) shown in FIG. 8 comprises: [0143] the
tunable passive antennas (11) (12) (13) (14) forming a multiport
antenna array (1) of FIG. 7; [0144] the sensing units (91) (92)
(93) (94) of FIG. 7; [0145] the multiple-input-port and
multiple-output-port network (3) of FIG. 7; [0146] the feeders (21)
(22) (23) (24) of FIG. 7; [0147] the signal processing unit (8) of
FIG. 7; [0148] the tuning control unit (4) of FIG. 7; and [0149] a
radio device (5) which consists of all parts of the transmitter (or
transceiver) which are not shown elsewhere in FIG. 8, the radio
device having m=4 radio ports, the radio device delivering "tuning
sequence instructions" which indicate when a tuning sequence is
being performed, m excitations being delivered by the radio ports
during said tuning sequence, one and only one of the excitations
being delivered by each of the radio ports.
[0150] In FIG. 8, each of the input ports of the
multiple-input-port and multiple-output-port network (3) is coupled
to one and only one of the radio ports, through one and only one of
the sensing units. The m radio ports see, at the given frequency,
an impedance matrix referred to as "the impedance matrix seen by
the radio ports", which clearly may be considered as being the
impedance matrix presented by the user ports and denoted by
Z.sub.U.
[0151] The radio device (5) performs functions which were, in the
explanations provided above about FIG. 7, assigned to the external
device. The tuning sequence instructions are delivered to the
signal processing unit (8). Additionally, the radio device provides
other signals to the signal processing unit, and/or receives other
signals from the signal processing unit.
Ninth Embodiment
[0152] As a ninth embodiment of a device of the invention, given by
way of non-limiting example, we have represented in FIG. 9 the
block diagram of an automatically tunable antenna array having m=4
user ports (912) (922) (932) (942), the m user ports presenting, at
a given frequency greater than or equal to 30 MHz, an impedance
matrix referred to as "the impedance matrix presented by the user
ports" and denoted by Z.sub.U, the automatically tunable antenna
array comprising: [0153] n=4 tunable passive antennas (11) (12)
(13) (14), each of the tunable passive antennas comprising at least
one antenna control device having at least one parameter having an
effect on one or more characteristics of said each of the tunable
passive antennas, said at least one parameter being adjustable by
electrical means; [0154] m sensing units (91) (92) (93) (94), each
of the sensing units delivering one or more "sensing unit output
signals", each of the sensing unit output signals being determined
by one electrical variable measured (or sensed) at one of the user
ports; [0155] a multiple-input-port and multiple-output-port tuning
unit (6) having m input ports and n output ports, each of the m
input ports being coupled to one and only one of the user ports
through one and only one of the sensing units, the
multiple-input-port and multiple-output-port tuning unit
comprisingp adjustable impedance devices, wherep is an integer
greater than or equal to m, the p adjustable impedance devices
being referred to as "the adjustable impedance devices of the
tuning unit" and being such that, at said given frequency, each of
the adjustable impedance devices of the tuning unit has a
reactance, the reactance of any one of the adjustable impedance
devices of the tuning unit having an influence on the impedance
matrix presented by the user ports, the reactance of any one of the
adjustable impedance devices of the tuning unit being adjustable by
electrical means; [0156] n feeders (21) (22) (23) (24), each of the
feeders having a first end coupled to a signal port of one and only
one of the tunable passive antennas, each of the feeders having a
second end coupled to one and only one of the n output ports;
[0157] a signal processing unit (8), the signal processing unit
estimating q real quantities depending on the impedance matrix
presented by the user ports, where q is an integer greater than or
equal to m, using the sensing unit output signals obtained for m
excitations applied by an external device to the user ports (the
external device is not shown in FIG. 9), one and only one of the
excitations being applied to each user ports, the excitations being
not applied successively, each of the excitations being a bandpass
signal, the signal processing unit delivering a "tuning
instruction" as a function of said q real quantities depending on
the impedance matrix presented by the user ports; and [0158] a
tuning control unit (4), the tuning control unit receiving the
tuning instruction from the signal processing unit (8), the tuning
control unit delivering "tuning control signals" to the tunable
passive antennas (11) (12) (13) (14) and to the multiple-input-port
and multiple-output-port tuning unit (6), the tuning control
signals being determined as a function of the tuning instruction,
each of said parameters being mainly determined by one or more of
the tuning control signals, the reactance of each of the adjustable
impedance devices of the tuning unit being mainly determined by one
or more of the tuning control signals.
[0159] The multiple-input-port and multiple-output-port tuning unit
(6) behaves, at the given frequency, with respect to its input
ports and output ports, substantially as a passive linear device,
where "passive" is used in the meaning of circuit theory. More
precisely, the multiple-input-port and multiple-output-port tuning
unit behaves, at the given frequency, with respect to the n output
ports and the m input ports, substantially as a passive linear
(n+m)-port device. As a consequence of linearity, it is possible to
define the impedance matrix presented by the input ports. As a
consequence of passivity, the multiple-input-port and
multiple-output-port tuning unit does not provide
amplification.
[0160] The multiple-input-port and multiple-output-port tuning unit
(6) allows, at the given frequency, transfers of power from its
input ports to its output ports and from its output ports to its
input ports, these transfers of power being ideally lossless, or
nearly lossless.
[0161] As said above, the reactance of an adjustable impedance
device may depend on the ambient temperature, for some types of
adjustable impedance devices. If such a type of adjustable
impedance device is used in the multiple-input-port and
multiple-output-port tuning unit, it is possible that the tuning
control signals are determined as a function of the tuning
instruction and as a function of one or more temperatures, to
compensate the effect of temperature on the reactance of each of
the adjustable impedance devices of the tuning unit. If such a type
of adjustable impedance device is used in the multiple-input-port
and multiple-output-port tuning unit, it is also possible that one
or more temperatures are taken into account to obtain the tuning
instruction, to compensate the effect of temperature on the
reactance of each of the adjustable impedance devices of the tuning
unit. In this case, the signal processing unit delivers the tuning
instruction as a function of said q real quantities depending on
the impedance matrix presented by the user ports, and as a function
of said one or more temperatures.
[0162] As shown in FIG. 9, it is possible to consider that each of
the sensing units (91) (92) (93) (94) includes: a first port
connected to one of said input ports; and a second port which is
one of the user ports (912) (922) (932) (942).
[0163] In this ninth embodiment, the antenna control devices are
MEMS switches, and the tunable passive antennas are used to obtain
a coarse adjustment of Z.sub.U, whereas the multiple-input-port and
multiple-output-port tuning unit is used to obtain a fine
adjustment of Z.sub.U.
[0164] As an example, FIG. 10 shows the block diagram of a
transmitter for radio communication (or of a transceiver for radio
communication) using the automatically tunable antenna array shown
in FIG. 9. The transmitter for radio communication (or transceiver
for radio communication) shown in FIG. 10 comprises: [0165] the
tunable passive antennas (11) (12) (13) (14) of FIG. 9; [0166] the
sensing units (91) (92) (93) (94) of FIG. 9; [0167] the
multiple-input-port and multiple-output-port tuning unit (6) of
FIG. 9; [0168] the feeders (21) (22) (23) (24) of FIG. 9; [0169]
the signal processing unit (8) of FIG. 9; [0170] the tuning control
unit (4) of FIG. 9; and [0171] a radio device (5) which consists of
all parts of the transmitter (or transceiver) which are not shown
elsewhere in FIG. 10, the radio device having m=4 radio ports, the
radio device delivering "tuning sequence instructions" which
indicate when a tuning sequence is being performed, m excitations
being delivered by the radio ports during said tuning sequence, one
and only one of the excitations being delivered by each of the
radio ports.
[0172] In FIG. 10, each of the input ports of the
multiple-input-port and multiple-output-port tuning unit (6) is
coupled to one and only one of the radio ports, through one and
only one of the sensing units. The m radio ports see, at the given
frequency, an impedance matrix referred to as "the impedance matrix
seen by the radio ports", which clearly may be considered as being
the impedance matrix presented by the user ports and denoted by
Z.sub.U.
[0173] The radio device (5) performs functions which were, in the
explanations provided above about FIG. 9, assigned to the external
device. The tuning sequence instructions are delivered to the
signal processing unit (8). Additionally, the radio device provides
other signals to the signal processing unit, and/or receives other
signals from the signal processing unit.
[0174] During a tuning sequence, each of the radio ports presents a
known impedance and the short-circuit current of the Norton
equivalent circuit of each of the radio ports is also known. Thus,
the specialist understands that the measurement of complex voltages
at the radio ports is sufficient to derive all entries of Z.sub.U.
Consequently, each of the sensing units (91) (92) (93) (94) may for
instance deliver a single sensing unit output signal proportional
to an electrical variable, the electrical variable being a voltage
across one of the radio ports, or equivalently a voltage across one
of the user ports.
Tenth Embodiment
[0175] The tenth embodiment of a device of the invention, given by
way of non-limiting example, also corresponds to the automatically
tunable antenna array having m=4 user ports (912) (922) (932) (942)
shown in FIG. 9, and all explanations provided for the ninth
embodiment are applicable to this tenth embodiment.
[0176] In this tenth embodiment, n=m, and the multiple-input-port
and multiple-output-port tuning unit is composed of m
single-input-port and single-output-port tuning units, each
comprising one or more of said adjustable impedance devices of the
tuning unit, or two or more of said adjustable impedance devices of
the tuning unit, these single-input-port and single-output-port
tuning units being independent and uncoupled. Such a
multiple-input-port and multiple-output-port tuning unit is for
instance considered in the section III of the article of F. Broyde
and E. Clavelier entitled "Two Multiple-Antenna-Port and
Multiple-User-Port Antenna Tuners", published in Proc. 9th European
Conference on Antenna and Propagation, EuCAP 2015, in April
2015.
[0177] The specialist understands that each of the n tunable
passive antennas is coupled, through one of the feeders, the
multiple-input-port and multiple-output-port tuning unit and one
and only one sensing unit, to one and only one of the user ports.
Consequently, each of the n tunable passive antennas is coupled,
indirectly, to one and only one of the user ports.
[0178] In this tenth embodiment, an adaptive process is implemented
by the signal processing unit, during one or more tuning sequences.
The adaptive process is the following: during each of said tuning
sequences, the signal processing unit estimates a norm of the
matrix of the voltage reflection coefficients at the user ports,
for a finite set of tuning instructions, and a tuning instruction
producing the smallest norm is selected. The specialist understands
that this adaptive process is easier to implement in the case where
each of the sensing units is such that the two sensing unit output
signals delivered by said each of the sensing units comprise: a
first sensing unit output signal proportional to an incident
voltage at one of the user ports; and a second sensing unit output
signal proportional to a reflected voltage at said one of the user
ports.
Eleventh Embodiment
[0179] The eleventh embodiment of a device of the invention, given
by way of non-limiting example, also corresponds to the
automatically tunable antenna array having m=4 user ports (912)
(922) (932) (942) shown in FIG. 9, and all explanations provided
for the ninth embodiment are applicable to this eleventh
embodiment.
[0180] In this eleventh embodiment, the multiple-input-port and
multiple-output-port tuning unit (6) is not composed of m
independent and uncoupled single-input-port and single-output-port
tuning units, each comprising one or more of said adjustable
impedance devices of the tuning unit.
[0181] More precisely, the multiple-input-port and
multiple-output-port tuning unit is an antenna tuning apparatus
disclosed in the French patent application No. 12/02542 and in the
international application PCT/IB2013/058423, and explained in: the
article of F. Broyde and E. Clavelier, entitled "A New
Multiple-Antenna-Port and Multiple-User-Port Antenna Tuner",
published in Proc. 2015 IEEE Radio & Wireless Week, RWW 2015,
at the pages 41 to 43, in January 2015; the article of F. Broyde
and E. Clavelier entitled "Some Properties ofMultiple-Antenna-Port
and Multiple-User-Port Antenna Tuners", published in IEEE Trans. on
Circuits and Systems--I: Regular Papers, Vol. 62, No. 2, pp.
423-432, in February 2015; and in said article of F. Broyde and E.
Clavelier entitled "Two Multiple-Antenna-Port and
Multiple-User-Port Antenna Tuners". Thus, the multiple-input-port
and multiple-output-port tuning unit is such that the reactance of
any one of the adjustable impedance devices of the tuning unit has,
at said given frequency, if the impedance matrix seen by the output
ports is equal to a given diagonal impedance matrix, an influence
on the impedance matrix presented by the input ports, and such that
the reactance of at least one of the adjustable impedance devices
of the tuning unit has, at said given frequency, if the impedance
matrix seen by the output ports is equal to the given diagonal
impedance matrix, an influence on at least one non-diagonal entry
of the impedance matrix presented by the input ports. This must be
interpreted as meaning: the multiple-input-port and
multiple-output-port tuning unit is such that, at said given
frequency, there exists a diagonal impedance matrix referred to as
the given diagonal impedance matrix, the given diagonal impedance
matrix being such that, if an impedance matrix seen by the output
ports is equal to the given diagonal impedance matrix, then (a) the
reactance of any one of the adjustable impedance devices of the
tuning unit has an influence on an impedance matrix presented by
the input ports, and (b) the reactance of at least one of the
adjustable impedance devices of the tuning unit has an influence on
at least one non-diagonal entry of the impedance matrix presented
by the input ports.
[0182] The specialist understands that each of the n tunable
passive antennas is coupled, through one of the feeders, the
multiple-input-port and multiple-output-port tuning unit and one or
more sensing units, to one or more of the user ports, and that at
least one of the n tunable passive antennas is coupled, through one
of the feeders, the multiple-input-port and multiple-output-port
tuning unit and two or more sensing units, to two or more of the
user ports. Consequently, each of the n tunable passive antennas is
coupled, indirectly, to one or more of the user ports, and at least
one of the n tunable passive antennas is coupled, indirectly, to
two or more of the user ports.
[0183] In this eleventh embodiment, an adaptive process is
implemented by the signal processing unit, during one or more
tuning sequences. A first possible adaptive process is the
following: during each of said tuning sequences, the signal
processing unit estimates the real part and the imaginary part of
the m.sup.2 entries of Z.sub.U, which are q=2m.sup.2 real
quantities depending on the impedance matrix presented by the user
ports; the signal processing unit computes the real part and the
imaginary part of the m.sup.2 entries of the admittance matrix
presented by the user ports, which is equal to Z.sub.U.sup.-1; and
the signal processing unit determines a tuning instruction such
that a norm of the image of this admittance matrix, computed as
said above, under a matrix function is reduced (so that we can also
say that a norm of the image of Z.sub.U under a matrix function is
reduced). A second possible adaptive process is the following:
during each of said tuning sequences, the signal processing unit
estimates the real part and the imaginary part of the m.sup.2
entries of the admittance matrix presented by the user ports, which
are q=2m.sup.2 real quantities depending on the impedance matrix
presented by the user ports; and the signal processing unit
determines a tuning instruction such that a norm of the image of
this admittance matrix, estimated as said above, under a matrix
function is reduced (so that we can also say that a norm of the
image of Z.sub.U under a matrix function is reduced). A third
possible adaptive process is the following: during each of said
tuning sequences, the signal processing unit estimates the real
part and the imaginary part of the m.sup.2 entries of the
admittance matrix presented by the user ports ; and the signal
processing unit determines a tuning instruction such that the
admittance matrix presented by the user ports is substantially
equal to a wanted admittance matrix equal to the inverse of
Z.sub.W.
[0184] The specialist understands that, in many possible
applications, the impedance matrix seen by the output ports is a
symmetric matrix, so that the impedance matrix presented by the
user ports and the admittance matrix presented by the user ports
are symmetric matrices which are each fully defined by m (m+1) real
quantities. Thus, only m (m+1) real quantities depending on the
impedance matrix presented by the user ports are needed to fully
define the impedance matrix presented by the user ports and the
admittance matrix presented by the user ports. The specialist
understands how the three possible adaptive processes defined above
can use this property and/or be modified to take advantage of this
property.
Twelfth Embodiment
[0185] The twelfth embodiment of a device of the invention, given
by way of non-limiting example, also corresponds to the
automatically tunable antenna array having m=4 user ports (912)
(922) (932) (942) shown in FIG. 9, and all explanations provided
for the ninth embodiment are applicable to this twelfth embodiment.
Additionally, in this twelfth embodiment, the signal processing
unit (8) delivers the "tuning instruction" as a function of said q
real quantities depending on the impedance matrix presented by the
user ports, and as a function of one or more localization
variables, each of the localization variables depending on the
distance between a part of a human body and a zone of a transmitter
for radio communication in which the automatically tunable antenna
array is built and used.
[0186] It is said above that each of the localization variables
depends on the distance between a part of a human body and a zone
of the transmitter for radio communication. This must be
interpreted as meaning: each of the localization variables is such
that there exists at least one configuration in which the distance
between a part of a human body and a zone of the transmitter for
radio communication has an effect on said each of the localization
variables.
[0187] For instance, a "localization sensor unit" may estimate one
or more localization variables each depending, in a given use
configuration, on the distance between a part of a human body and a
zone of the transmitter for radio communication. The localization
sensor unit may comprise a plurality of localization sensors. Each
of said zones may be a part of the space occupied by the
corresponding localization sensor, this space being inside the
space occupied by the transmitter for radio communication, so that
in this case each of said zones has a volume much less than the
volume of the transmitter for radio communication. For each of the
antennas, at least one of the localization variables may depend on
the distance between a part of a human body and a small zone near
said each of the antennas. If a suitable localization sensor is
used, said zone may be a point, or substantially a point.
[0188] For instance, at least one of the localization variables may
be an output of a localization sensor responsive to a pressure
exerted by a part of a human body. For instance, at least one of
the localization variables may be an output of a proximity
sensor.
[0189] The localization sensor unit assesses (or equivalently,
estimates) a plurality of localization variables each depending, in
a given use configuration, on the distance between a part of a
human body and a zone of the transmitter for radio communication.
However, it is possible that one or more other localization
variables each depending, in a given use configuration, on the
distance between a part of a human body and a zone of the
transmitter for radio communication, are not estimated by the
localization sensor unit. For instance, at least one of the
localization variables may be determined by a change of state of an
output of a touchscreen. Thus, the localization sensor unit may be
regarded as a part of a localization unit which estimates (or
evaluates) a plurality of variables, each of said variables being
referred to as "localization variable", each of the localization
variables depending on the distance between a part of a human body
and a zone of the transmitter for radio communication. This part of
the localization unit may be the whole localization unit.
[0190] This twelfth embodiment may possibly use some aspects of the
technique disclosed in the French patent application No. 14/00606
of 13 March 2014 entitled "Communication radio utilisant des
antennes multiples et des variables de localisation", corresponding
to the international application No. PCT/IB2015/051548 of 3 Mar.
2015 entitled "Radio communication using multiple antennas and
localization variables".
Thirteenth Embodiment
[0191] As a thirteenth embodiment of a device of the invention,
given by way of non-limiting example, we have represented in FIG.
11 the block diagram of an automatically tunable antenna array
having m=2 user ports (912) (922), the m user ports presenting, at
a given frequency greater than or equal to 300 MHz, an impedance
matrix referred to as "the impedance matrix presented by the user
ports" and denoted by Z.sub.U, the automatically tunable antenna
array comprising: [0192] n=4 tunable passive antennas (11) (12)
(13) (14), the n tunable passive antennas forming a multiport
antenna array (1), each of the tunable passive antennas comprising
at least one antenna control device, said at least one antenna
control device having at least one parameter having an effect on
one or more characteristics of said each of the tunable passive
antennas, said at least one parameter being adjustable by
electrical means; [0193] a switching unit (7), the switching unit
receiving a "configuration instruction" delivered by an external
device (the external device is not shown in FIG. 11), the switching
unit comprising n antenna ports each coupled to one and only one of
the tunable passive antennas through a feeder (21) (22) (23) (24),
the switching unit comprising N=2 array ports, the switching unit
operating in an active configuration determined by the
configuration instruction, the active configuration being one of a
plurality of allowed configurations, the switching unit providing,
in any one of the allowed configurations, for signals in a given
frequency band and for any one of the array ports, a bidirectional
path between said any one of the array ports and one and only one
of the antenna ports; [0194] m sensing units (91) (92), each of the
sensing units delivering two or more "sensing unit output signals",
each of the sensing unit output signals being determined by one
electrical variable; [0195] a multiple-input-port and
multiple-output-port tuning unit (6) having m input ports and N
output ports, each of the m input ports being coupled to one and
only one of the user ports through one and only one of the sensing
units, each of the N output ports being coupled to one and only one
of the array ports, the multiple-input-port and
multiple-output-port tuning unit comprisingp adjustable impedance
devices, where p is an integer greater than or equal to m, the p
adjustable impedance devices being referred to as "the adjustable
impedance devices of the tuning unit" and being such that, at said
given frequency, each of the adjustable impedance devices of the
tuning unit has a reactance, the reactance of any one of the
adjustable impedance devices of the tuning unit having an influence
on the impedance matrix presented by the user ports, the reactance
of any one of the adjustable impedance devices of the tuning unit
being adjustable by electrical means; [0196] a signal processing
unit (8), the signal processing unit estimating q real quantities
depending on the impedance matrix presented by the user ports,
where q is an integer greater than or equal to m, using the sensing
unit output signals obtained for m excitations applied by said
external device to the user ports, one and only one of the
excitations being applied to each user ports, the excitations being
not applied successively, each of the excitations being a bandpass
signal, the signal processing unit delivering a "tuning
instruction" as a function of said q real quantities depending on
the impedance matrix presented by the user ports; and [0197] a
tuning control unit (4), the tuning control unit receiving the
tuning instruction from the signal processing unit (8), the tuning
control unit delivering "tuning control signals" to the tunable
passive antennas (11) (12) (13) (14) and to the multiple-input-port
and multiple-output-port tuning unit (6), the tuning control
signals being determined as a function of the tuning instruction,
each of said parameters being mainly determined by one or more of
the tuning control signals, the reactance of each of the adjustable
impedance devices of the tuning unit being mainly determined by one
or more of the tuning control signals.
[0198] The switching unit operates (or is used) in an active
configuration determined by the configuration instruction, the
active configuration being one of a plurality of allowed
configurations, the switching unit providing, in any one of the
allowed configurations, for signals in the given frequency band and
for any one of the array ports, a path between said any one of the
array ports and one of the antenna ports. Thus, the switching unit
operates in an active configuration which is one of the allowed
configurations, and each allowed configuration corresponds to a
selection of N antenna ports among the n antenna ports. It is also
possible to say that the switching unit operates in an active
configuration corresponding to a selection of N antenna ports among
the n antenna ports.
[0199] Each allowed configuration corresponds to a selection of N
antenna ports among the n antenna ports, the switching unit
providing, for signals in the given frequency band and for any one
of the array ports, a path between said any one of the array ports
and one of the selected antenna ports. This path may preferably be
a low loss path for signals in the given frequency band. The
specialist understands that a suitable switching unit may comprise
one or more electrically controlled switches and/or change-over
switches (here, "electrically controlled" means "controlled by
electrical means"). In this case, one or more of said electrically
controlled switches and/or change-over switches may for instance be
an electro-mechanical relay, or a microelectromechanical switch, or
a circuit using one or more PIN diodes and/or one or more
insulated-gate field-effect transistors as switching devices.
[0200] In this embodiment, it is not possible to say that, for each
of the n tunable passive antennas, the signal port of the antenna
is coupled, directly or indirectly, to one and only one of the user
ports. However, in this embodiment, for each of the m user ports,
the user port is indirectly coupled to one and only one of the n
tunable passive antennas.
[0201] For instance, the configuration instruction may be
determined as a function of: [0202] one or more localization
variables defined as in the twelfth embodiment; [0203] the
frequencies used for radio communication with the tunable passive
antennas; [0204] one or more additional variables, each of the
additional variables lying in a set of additional variables, the
elements of the set of additional variables comprising:
communication type variables which indicate whether a radio
communication session is a voice communication session, a data
communication session or another type of communication session; a
speakerphone mode activation indicator; a speaker activation
indicator; variables obtained using one or more accelerometers;
user identity variables which depend on the identity of the current
user; reception quality variables; and emission quality
variables.
[0205] The elements of said set of additional variables may further
comprise one or more variables which are different from the
localization variables and which characterize the grip with which a
user is holding the transmitter for radio communication.
[0206] The configuration instruction may for instance be determined
using a lookup table.
[0207] In order to respond to variations in the electromagnetic
characteristics of the volume surrounding the antennas, the
configuration instruction and/or the tuning instruction and/or the
tuning control signals may be generated repeatedly and delivered
repeatedly, for instance every 10 milliseconds.
[0208] As an example, FIG. 12 shows the block diagram of a
transmitter for radio communication (or of a transceiver for radio
communication) using the automatically tunable antenna array shown
in FIG. 11. The transmitter for radio communication (or transceiver
for radio communication) shown in FIG. 12 comprises: [0209] the
tunable passive antennas (11) (12) (13) (14) forming a multiport
antenna array (1) of FIG. 11; [0210] the switching unit (7) of FIG.
11; [0211] the feeders (21) (22) (23) (24) of FIG. 11; [0212] the
sensing units (91) (92) of FIG. 11; [0213] the multiple-input-port
and multiple-output-port tuning unit (6) of FIG. 11; [0214] the
signal processing unit (8) of FIG. 11; [0215] the tuning control
unit (4) of FIG. 11; and [0216] a radio device (5) which consists
of all parts of the transmitter (or transceiver) which are not
shown elsewhere in FIG. 12, the radio device having m=2 radio
ports, the radio device delivering the configuration instruction,
the radio device delivering "tuning sequence instructions" which
indicate when a tuning sequence is being performed, m excitations
being delivered by the radio ports during said tuning sequence, one
and only one of the excitations being delivered by each of the
radio ports.
[0217] In FIG. 12, each of the input ports of the
multiple-input-port and multiple-output-port tuning unit (6) is
coupled to one and only one of the radio ports, through one and
only one of the sensing units. The m radio ports see, at the given
frequency, an impedance matrix referred to as "the impedance matrix
seen by the radio ports", which clearly may be considered as being
the impedance matrix presented by the user ports and denoted by
Z.sub.U.
[0218] The radio device (5) performs functions which were, in the
explanations provided above about FIG. 11, assigned to the external
device. The configuration instruction is delivered to the switching
unit (7). The tuning sequence instructions are delivered to the
signal processing unit (8). Additionally, the radio device provides
other signals to the signal processing unit, and/or receives other
signals from the signal processing unit.
[0219] This thirteenth embodiment may possibly use some aspects of
the technique disclosed in the French patent application No.
14/01221 of 28 May 2014, entitled "Communication radio utilisant
une pluralite d'antennes selectionnees", corresponding to the
international application No. PCT/IB2015/052974 of 23 Apr. 2015,
entitled "Radio communication using a plurality of selected
antennas".
INDICATIONS ON INDUSTRIAL APPLICATIONS
[0220] The method of the invention is suitable for optimally and
automatically adjusting a plurality of tunable passive antennas,
and the automatically tunable antenna array of the invention can
optimally and automatically adjust its tunable passive
antennas.
[0221] The automatically tunable antenna array of the invention may
for instance be a part of a radio transmitter using a plurality of
antennas simultaneously, or of a radio transceiver using a
plurality of antennas simultaneously. In such applications, each
user port of the automatically tunable antenna array of the
invention may be coupled to one of the radio-frequency signal
output ports of the radio transmitter using a plurality of antennas
simultaneously, or to one of the radio-frequency signal
input/output ports of the radio transceiver using a plurality of
antennas simultaneously. Thus, the method and the automatically
tunable antenna array of the invention are suitable for MIMO radio
communication.
[0222] The method and the automatically tunable antenna array of
the invention provide the best possible characteristics using very
close tunable passive antennas, hence presenting a strong
interaction between them. The invention is therefore particularly
suitable for mobile radio transmitters and transceivers, for
instance those used in portable radiotelephones or portable
computers.
[0223] The method and the automatically tunable antenna array of
the invention provide the best possible characteristics using a
very large number of tunable passive antennas in a given volume,
hence presenting a strong interaction between them. The invention
is therefore particularly suitable for high-performance radio
transmitters and transceivers, for instance those used in the fixed
stations of cellular radiotelephony networks.
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