U.S. patent application number 15/670872 was filed with the patent office on 2017-11-23 for antennaless wireless device.
The applicant listed for this patent is Fractus Antennas, S.L.. Invention is credited to Aurora ANDUJAR LINARES, Jaume ANGUERA PROS, Josep MUMBRU, Carles PUENTE BALIARDA.
Application Number | 20170338561 15/670872 |
Document ID | / |
Family ID | 42370950 |
Filed Date | 2017-11-23 |
United States Patent
Application |
20170338561 |
Kind Code |
A1 |
ANGUERA PROS; Jaume ; et
al. |
November 23, 2017 |
Antennaless Wireless Device
Abstract
A radiating system of a wireless device transmits and receives
electromagnetic wave signals in a frequency region and comprises an
external port, a radiating structure, and a radiofrequency system.
The radiating structure includes: a ground plane layer with a
connection point; a radiation booster with a connection point and
being smaller than 1/30 of a free-space wavelength corresponding to
a lowest frequency of the frequency region; and an internal port
between the radiation booster connection point and the ground plane
layer connection point. The radiofrequency system includes: a first
port connected to the radiating structure's internal port; and a
second port connected to the external port. An input impedance at
radiating structure's disconnected internal port has a non-zero
imaginary part across the frequency region. The radiofrequency
system modifies impedance of the radiating structure to provide
impedance matching to the radiating system within the frequency
region at the external port.
Inventors: |
ANGUERA PROS; Jaume;
(Vinaros, ES) ; ANDUJAR LINARES; Aurora;
(Barcelona, ES) ; PUENTE BALIARDA; Carles;
(Barcelona, ES) ; MUMBRU; Josep;
(Asnieres-sur-Seine, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Fractus Antennas, S.L. |
Sant Cugat del Valles |
|
ES |
|
|
Family ID: |
42370950 |
Appl. No.: |
15/670872 |
Filed: |
August 7, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
15004151 |
Jan 22, 2016 |
9761944 |
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15670872 |
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|
14738115 |
Jun 12, 2015 |
9276307 |
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|
15004151 |
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|
|
13476503 |
May 21, 2012 |
9130259 |
|
|
14738115 |
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12669147 |
Jan 14, 2010 |
8203492 |
|
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PCT/EP09/05579 |
Jul 31, 2009 |
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13476503 |
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61142523 |
Jan 5, 2009 |
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61086838 |
Aug 7, 2008 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01Q 1/243 20130101;
H01Q 5/00 20130101; H01Q 1/50 20130101; H01Q 1/48 20130101; H01Q
9/0407 20130101; H05K 999/99 20130101; H01Q 5/50 20150115; H01Q
5/35 20150115; H01Q 5/335 20150115 |
International
Class: |
H01Q 5/50 20060101
H01Q005/50; H01Q 5/00 20060101 H01Q005/00; H01Q 1/48 20060101
H01Q001/48; H01Q 5/335 20060101 H01Q005/335; H01Q 1/24 20060101
H01Q001/24; H01Q 5/35 20060101 H01Q005/35; H01Q 9/04 20060101
H01Q009/04; H01Q 1/50 20060101 H01Q001/50 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 4, 2008 |
EP |
08161722.7 |
Dec 24, 2008 |
EP |
08172925.3 |
Jul 13, 2009 |
ES |
P200930444 |
Jul 24, 2009 |
ES |
P200930499 |
Claims
1. A radiation booster comprising: a volumetric geometry including
a first conductive part on one surface of the radiation booster,
and a second conductive part on a second surface of the radiation
booster parallel to the first surface, both of the first and second
conductive parts including a polygonal contour, the second
conductive part including a soldering pad connected to the first
conductive part by a conductive circuit, the soldering pad and
conductive circuit being located substantially close to a corner of
the radiation booster, wherein the distance between the first
conductive part and the soldering pad is 5 mm or less, wherein a
longest edge of the radiation booster is shorter than 1/30 of a
longest operating wavelength of a lowest operating frequency band
at which the radiation booster operates, wherein the radiation
booster is configured to being mounted near an edge of a ground
plane layer on a printed circuit board of a wireless device, such
that a gap with no conductor is between the edge and the radiation
booster and no projection of the radiation booster onto the printed
circuit board intersects the ground plane, and wherein the
radiation booster is configured to be connected to a matching
network, the matching network providing impedance matching in at
least a first frequency region of operation, the matching network
including at least three circuit components including an inductor
and a capacitor.
2. The radiation booster according to claim 1, wherein the first
frequency region includes the 824-960 MHz frequency range.
3. The radiation booster according to claim 1, wherein the first
frequency region includes the LTE frequency band.
4. The radiation booster according to claim 3, wherein the LTE
frequency band includes the 700 MHz frequency.
5. The radiation booster according to claim 1, wherein the
polygonal shape is rectangular.
6. The radiation booster according to claim 1, wherein the
radiation booster is configured to operate at a second frequency
band.
7. The radiation booster according to claim 6, wherein the second
frequency band includes the 1710-1890 MHz frequency range.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 15/004,151, filed Jan. 22, 2016, which is a
continuation of U.S. patent application Ser. No. 14/738,115 filed
Jun. 12, 2015, issued as U.S. Pat. No. 9,276,307, on Mar. 1, 2016,
which is a continuation of U.S. patent application Ser. No.
13/476,503 filed May 21, 2012, issued as U.S. Pat. No. 9,130,259,
on Sep. 8, 2015, which is a continuation of U.S. patent application
Ser. No. 12/669,147 filed Jan. 14, 2010, issued as U.S. Pat. No.
8,203,492, on Jun. 19, 2012, which is a 371 national phase of
International application No. PCT/EP2009/005579, filed Jul. 31,
2009, which claims the benefit of U.S. Provisional Application No.
61/142,523, filed on Jan. 5, 2009, and also claims the benefit of
U.S. Provisional Application No. 61/086,838, filed on Aug. 7, 2008,
the entire contents of which are hereby incorporated by
reference.
FIELD OF THE INVENTION
[0002] The present invention relates to the field of wireless
handheld devices, and generally to wireless portable devices which
require the transmission and reception of electromagnetic wave
signals.
BACKGROUND
[0003] Wireless handheld or portable devices typically operate one
or more cellular communication standards and/or wireless
connectivity standards, each standard being allocated in one or
more frequency bands, and said frequency bands being contained
within one or more regions of the electromagnetic spectrum.
[0004] For that purpose, a space within the wireless handheld or
portable device is usually dedicated to the integration of a
radiating system. The radiating system is, however, expected to be
small in order to occupy as little space as possible within the
device, which then allows for smaller devices, or for the addition
of more specific equipment and functionality into the device.
[0005] At the same time, it is sometimes required for the radiating
system to be flat since this allows for slim devices or in
particular, for devices which have two parts that can be shifted or
twisted against each other.
[0006] Many of the demands for wireless handheld or portable
devices also translate to specific demands for the radiating
systems thereof.
[0007] A typical wireless handheld device must include a radiating
system capable of operating in one ore more frequency regions with
good radioelectric performance (such as for example in terms of
input impedance level, impedance bandwidth, gain, efficiency, or
radiation pattern). Moreover, the integration of the radiating
system within the wireless handheld device must be correct to
ensure that the wireless device itself attains a good radioelectric
performance (such as for example in terms of radiated power,
received power, or sensitivity).
[0008] This is even more critical in the case in which the wireless
handheld device is a multifunctional wireless device.
Commonly-owned patent U.S. Pat. No. 8,738,103 and patent
publication WO2008/009391 and describe a multifunctional wireless
device. The entire disclosure of said patent publication numbers
WO2008/009391 and U.S. Pat. No. 8,738,103 are hereby incorporated
by reference.
[0009] For a good wireless connection, high gain and efficiency are
further required. Other more common design demands for radiating
systems are the voltage standing wave ratio (VSWR) and the
impedance which is supposed to be about 50 ohms.
[0010] Other demands for radiating systems for wireless handheld or
portable devices are low cost and a low specific absorption rate
(SAR).
[0011] Furthermore, a radiating system has to be integrated into a
device or in other words a wireless handheld or portable device has
to be constructed such that an appropriate radiating system may be
integrated therein which puts additional constraints by
consideration of the mechanical fit, the electrical fit and the
assembly fit.
[0012] Of further importance, usually, is the robustness of the
radiating system which means that the radiating system does not
change its properties upon smaller shocks to the device.
[0013] A radiating system for a wireless device typically includes
a radiating structure comprising an antenna element which operates
in combination with a ground plane layer providing a determined
radioelectric performance in one or more frequency regions of the
electromagnetic spectrum. This is illustrated in FIG. 28, in which
it is shown a conventional radiating structure 2800 comprising an
antenna element 2801 and a ground plane layer 2802. Typically, the
antenna element has a dimension close to an integer multiple of a
quarter of the wavelength at a frequency of operation of the
radiating structure, so that the antenna element is at resonance at
said frequency and a radiation mode is excited on said antenna
element.
[0014] Although the radiating structure is usually very efficient
at the resonance frequency of the antenna element and maintains a
similar performance within a frequency range defined around said
resonance frequency (or resonance frequencies), outside said
frequency range the efficiency and other relevant antenna
parameters deteriorate with an increasing distance to said
resonance frequency.
[0015] Furthermore, the radiating structure operating at a
resonance frequency of the antenna element is typically very
sensitive to external effects (such as for instance the presence of
plastic or dielectric covers that surround the wireless device), to
components of the wireless device (such as for instance, but not
limited to, a speaker, a microphone, a connector, a display, a
shield can, a vibrating module, a battery, or an electronic module
or subsystem) placed either in the vicinity of, or even underneath,
the antenna element, and/or to the presence of the user of the
wireless device.
[0016] Any of the above mentioned aspects may alter the current
distribution and/or the electromagnetic field distribution of a
radiation mode of the antenna element, which usually translates
into detuning effects, degradation of the radioelectric performance
of the radiating structure and/or the radioelectric performance
wireless device, and/or greater interaction with the user (such as
an increased level of SAR).
[0017] A further problem associated to the integration of the
radiating structure, and in particular to the integration of the
antenna element, in a wireless device is that the volume dedicated
for such an integration has continuously shrunk with the appearance
of new smaller and/or thinner form factors for wireless devices,
and with the increasing convergence of different functionality in a
same wireless device.
[0018] Some techniques to miniaturize and/or optimize the multiband
behavior of an antenna element have been described in the prior
art. However, the radiating structures therein described still rely
on exciting a radiation mode on the antenna element.
[0019] For example, commonly-owned patent U.S. Pat. No. 7,554,490
describes a new family of antennas based on the geometry of
space-filling curves. Also, commonly-owned patent U.S. Pat. No.
7,528,782 relates to a new family of antennas, referred to as
multilevel antennas, formed by an electromagnetic grouping of
similar geometrical elements. The entire disclosures of the
aforesaid patent numbers U.S. Pat. No. 7,554,490 and U.S. Pat. No.
7,528,782 are hereby incorporated by reference.
[0020] Some other attempts have focused on antenna elements not
requiring a complex geometry while still providing some degree of
miniaturization by using an antenna element that is not resonant in
the one or more frequency ranges of operation of the wireless
device.
[0021] For example, WO2007/128340 discloses a wireless portable
device comprising a non-resonant antenna element for receiving
broadcast signals (such as, for instance, DVB-H, DMB, T-DMB or FM).
The wireless portable device further comprises a ground plane layer
that is used in combination with said antenna element. Although the
antenna element has a first resonance frequency above the frequency
range of operation of the wireless device, the antenna element is
still the main responsible for the radiation process and for the
electromagnetic performance of the wireless device. This is clear
from the fact that no radiation mode can be excited on the ground
plane layer because the ground plane layer is electrically short at
the frequencies of operation (i.e., its dimensions are much smaller
than the wavelength).
[0022] With such limitations, while the performance of the wireless
portable device may be sufficient for reception of electromagnetic
wave signals (such as those of a broadcast service), the antenna
element could not provide an adequate performance (for example, in
terms of input return losses or gain) for a cellular communication
standard requiring also the transmission of electromagnetic wave
signals.
[0023] Commonly-owned patent publication WO2008/119699 and
US2010/0109955 describe a wireless handheld or portable device
comprising a radiating system capable of operating in two frequency
regions. The radiating system comprises an antenna element having a
resonance frequency outside said two frequency regions, and a
ground plane layer. In this wireless device, while the ground plane
layer contributes to enhance the electromagnetic performance of the
radiating system in the two frequency regions of operation, it is
still necessary to excite a radiation mode on the antenna element.
In fact, the radiating system relies on the relationship between a
resonance frequency of the antenna element and a resonance
frequency of the ground plane layer in order for the radiating
system to operate properly in said two frequency regions.
[0024] The entire disclosure of the aforesaid patent publication
number WO2008/119699 and US2010/0109955 are hereby incorporated by
reference.
[0025] Some further techniques to enhance the behavior of an
antenna element relate to optimizing the geometry of a ground plane
layer associated to said antenna element. For example,
commonly-owned patent U.S. Pat. No. 7,688,276 describes a new
family of ground plane layers based on the geometry of multilevel
structures and/or space-filling curves. The entire disclosure of
the aforesaid patent U.S. Pat. No. 7,688,276 is hereby incorporated
by reference.
[0026] Another limitation of current wireless handheld or portable
devices relates to the fact that the design and integration of an
antenna element for a radiating structure in a wireless device is
typically customized for each device. Different form factors or
platforms, or a different distribution of the functional blocks of
the device will force to redesign the antenna element and its
integration inside the device almost from scratch.
[0027] For at least the above reasons, wireless device
manufacturers regard the volume dedicated to the integration of the
radiating structure, and in particular the antenna element, as
being a toll to pay in order to provide wireless capabilities to
the handheld or portable device.
SUMMARY
[0028] Therefore, a wireless device not requiring an antenna
element would be advantageous as it would ease the integration of
the radiating structure into the wireless handheld or portable
device. The volume freed up by the absence of the antenna element
would enable smaller and/or thinner devices, or even to adopt
radically new form factors which are not feasible today due to the
presence of an antenna element. Furthermore, by eliminating
precisely the element that requires customization, a standard
solution is obtained which only requires minor adjustments to be
implemented in different wireless devices.
[0029] A wireless handheld or portable device that does not require
of an antenna element, yet the wireless device featuring an
adequate radioelectric performance would be an advantageous
solution. This problem is solved by an antennaless wireless
handheld or portable device according to the present invention.
[0030] It is an object of the present invention to provide a
wireless handheld or portable device (such as for instance but not
limited to a mobile phone, a smartphone, a PDA, an MP3 player, a
headset, a USB dongle, a laptop computer, a gaming device, a
digital camera, a PCMCIA or Cardbus 32 card, or generally a
multifunction wireless device) which does not require an antenna
element for the transmission and reception of electromagnetic wave
signals. Such an antennaless wireless device is yet capable of
operation in one or more frequency regions of the electromagnetic
spectrum with enhanced radioelectric performance, increased
robustness to external effects and neighboring components of the
wireless device, and/or reduced interaction with the user.
[0031] Another object of the invention relates to a method to
enable the operation of a wireless handheld or portable device in
one or more frequency regions of the electromagnetic spectrum with
enhanced radioelectric performance, increased robustness to
external effects and neighboring components of the wireless device,
and/or reduced interaction with the user, without requiring the use
of an antenna element.
[0032] An antennaless wireless handheld or portable device
according to the present invention operates one, two, three, four
or more cellular communication standards (such as for example GSM
850, GSM 900, GSM 1800, GSM 1900, UMTS, HSDPA, CDMA, W-CDMA, LTE,
CDMA2000, TD-SCDMA, etc.), wireless connectivity standards (such as
for instance WiFi, IEEE802.11 standards, Bluetooth, ZigBee, UWB,
WiMAX, WiBro, or other high-speed standards), and/or broadcasts
standards (such as for instance FM, DAB, XDARS, SDARS, DVB-H, DMB,
T-DMB, or other related digital or analog video and/or audio
standards), each standard being allocated in one or more frequency
bands, and said frequency bands being contained within one, two,
three or more frequency regions of the electromagnetic
spectrum.
[0033] In the context of this document, a frequency band preferably
refers to a range of frequencies used by a particular cellular
communication standard, a wireless connectivity standard or a
broadcast standard; while a frequency region preferably refers to a
continuum of frequencies of the electromagnetic spectrum. For
example, the GSM 1800 standard is allocated in a frequency band
from 1710 MHz to 1880 MHz while the GSM 1900 standard is allocated
in a frequency band from 1850 MHz to 1990 MHz. A wireless device
operating the GSM 1800 and the GSM 1900 standards must have a
radiating system capable of operating in a frequency region from
1710 MHz to 1990 MHz.
[0034] The antennaless wireless handheld or portable device
according to the present invention may have a candy-bar shape,
which means that its configuration is given by a single body. It
may also have a two-body configuration such as a clamshell,
flip-type, swivel-type or slider structure. In some other cases,
the device may have a configuration comprising three or more
bodies. It may further or additionally have a twist configuration
in which a body portion (e.g. with a screen) can be twisted (i.e.,
rotated around two or more axes of rotation which are preferably
not parallel).
[0035] For a wireless handheld or portable device which is slim
and/or whose configuration comprises two or more bodies, the
requirements on maximum height of the antenna element are very
stringent, as the maximum thickness of each of the two or more
bodies of the device may be limited to 5, 6, 7, 8 or 9 mm. The
technology disclosed herein makes it possible for a wireless
handheld or portable device to feature an enhanced radioelectric
performance without requiring an antenna element, thus solving the
space constraint problems associated to such devices.
[0036] In the context of the present document a wireless handheld
or portable device is considered to be slim if it has a thickness
of less than 14 mm, 13 mm, 12 mm, 11 mm, 10 mm, 9 mm or 8 mm.
[0037] According to the present invention, an antennaless wireless
handheld or portable device advantageously comprises at least five
functional blocks: a user interface module, a processing module, a
memory module, a communication module and a power management
module. The user interface module comprises a display, such as a
high resolution LCD, OLED or equivalent, and is an energy consuming
module, most of the energy drain coming typically from the
backlight use. The user interface module may also comprise a keypad
and/or a touchscreen, and/or an embedded stylus pen. The processing
module, that is a microprocessor or a CPU, and the associated
memory module are also major sources of power consumption. The
fourth module responsible of energy consumption is the
communication module, an essential part of which is the radiating
system. The power management module of the antennaless wireless
handheld or portable device includes a source of energy (such as
for instance, but not limited to, a battery or a fuel cell) and a
power management circuit that manages the energy of the device.
[0038] In accordance with the present invention, the communication
module of the antennaless wireless handheld or portable device
includes a radiating system capable of transmitting and receiving
electromagnetic wave signals in a first frequency region. Said
radiating system comprises a radiating structure comprising at
least one ground plane layer including a connection point, at least
one radiation booster including a connection point and an internal
port. The internal port is defined between the connection point of
the at least one radiation booster and the connection point of the
at least one ground plane layer. The radiating system further
comprises a radiofrequency system, and an external port.
[0039] In some cases, the radiating system of an antennaless
wireless handheld or portable device comprises a radiating
structure consisting of at least one ground plane layer including a
connection point, at least one radiation booster including a
connection point and an internal port.
[0040] The radiofrequency system comprises a first port connected
to the internal port of the radiating structure and a second port
connected to the external port of the radiating system. Said
radiofrequency system modifies the impedance of the radiating
structure, providing impedance matching to the radiating system in
the at least the first frequency region of operation of the
radiating system.
[0041] In this text, a port of the radiating structure is referred
to as an internal port; while a port of the radiating system is
referred to as an external port. In this context, the terms
"internal" and "external" when referring to a port are used simply
to distinguish a port of the radiating structure from a port of the
radiating system, and carry no implication as to whether a port is
accessible from the outside or not.
[0042] An aspect of the present invention relates to the use of the
ground plane layer of the radiating structure as an efficient
radiator to provide an enhanced radioelectric performance in one or
more frequency regions of operation of the wireless handheld or
portable device, eliminating thus the need for an antenna element.
A radiation mode of the ground plane layer can be advantageously
excited when a dimension of said ground plane layer is on the order
of, or even larger than, one half of the wavelength corresponding
to a frequency of operation of the radiating system.
[0043] Therefore, in an antennaless wireless device according to
the present invention, no other parts or elements of the wireless
handheld or portable device have significant contribution to the
radiation process.
[0044] In some embodiments, said radiation mode occurs at a
frequency advantageously located above (i.e., at a frequency higher
than) the first frequency region of operation of the wireless
handheld or portable device. In some other embodiments, the
frequency of said radiation mode is within said first frequency
region.
[0045] A ground plane rectangle is defined as being the
minimum-sized rectangle that encompasses a ground plane layer of
the radiating structure. That is, the ground plane rectangle is a
rectangle whose sides are tangent to at least one point of said
ground plane layer.
[0046] In some cases, the ratio between a side of the ground plane
rectangle, preferably a long side of the ground plane rectangle,
and the free-space wavelength corresponding to the lowest frequency
of the first frequency region is advantageously larger than a
minimum ratio. Some possible minimum ratios are 0.1, 0.16, 0.2,
0.3, 0.4, 0.5, 0.6, 0.8, 1, 1.2 and 1.4. Said ratio may
additionally be smaller than a maximum ratio (i.e., said ratio may
be larger than a minimum ratio but smaller than a maximum ratio).
Some possible maximum ratios are 0.4, 0.5, 0.6, 0.8, 1, 1.2, 1.4,
1.6, 2, 3, 4, 5, 6, 8 and 10.
[0047] Setting a dimension of the ground plane rectangle,
preferably the dimension of its long side, relative to the
wavelength within these ranges makes it possible for the ground
plane layer to support an efficient radiation mode, in which the
currents flowing on the ground plane layer are substantially
aligned and contribute in phase to the radiation process.
[0048] The gain of a radiating structure depends on factors such as
its directivity, its radiating efficiency and its input return
loss. Both the radiating efficiency and the input return loss of
the radiating structure are frequency dependent (even directivity
is strictly frequency dependent). A radiating structure is usually
very efficient around the frequency of a radiation mode excited in
the ground plane layer and maintains a similar radioelectric
performance within the frequency range defined by its impedance
bandwidth around said frequency. Since the dimensions of the ground
plane layer (or those of the ground plane rectangle) are comparable
to, or larger than, the wavelength at the frequencies of operation
of the wireless device, said radiation mode may be efficient over a
broad range of frequencies.
[0049] In this text, the expression impedance bandwidth is to be
interpreted as referring to a frequency region over which a
wireless handheld or portable device and a radiating system comply
with certain specifications, depending on the service for which the
wireless device is adapted. For example, for a device adapted to
transmit and receive signals of cellular communication standards, a
radiating system having a relative impedance bandwidth of at least
5% (and more preferably not less than 8%, 10%, 15% or 20%) together
with an efficiency of not less than 30% (advantageously not less
than 40%, more advantageously not less than 50%) can be preferred.
Also, an input return-loss of -3 dB or better within the
corresponding frequency region can be preferred.
[0050] A wireless handheld or portable device generally comprises
one, two, three or more multilayer printed circuit boards (PCBs) on
which to carry the electronics. In a preferred embodiment of an
antennaless wireless handheld or portable device, the ground plane
layer of the radiating structure is at least partially, or
completely, contained in at least one of the layers of a multilayer
PCB.
[0051] In some cases, a wireless handheld or portable device may
comprise two, three, four or more ground plane layers. For example
a clamshell, flip-type, swivel-type or slider-type wireless device
may advantageously comprise two PCBs, each including a ground plane
layer.
[0052] The at least one radiation booster couples the
electromagnetic energy from the radiofrequency system to the ground
plane layer in transmission, and from the ground plane layer to the
radiofrequency system in reception. Thereby the radiation booster
boosts the radiation or reception of electromagnetic radiation.
[0053] In some examples, the at least one radiation booster has a
maximum size smaller than 1/30, 1/40, 1/50, 1/60, 1/80, 1/100,
1/140 or even 1/180 times the free-space wavelength corresponding
to the lowest frequency of the first frequency region of operation
of the antennaless wireless handheld or portable device.
[0054] In the prior art in general an antenna element is said to be
small (or miniature) when it can be fitted in a small space
compared to a given operating wavelength. More precisely, a
radiansphere is usually taken as the reference for classifying
whether an antenna element is small. The radiansphere is an
imaginary sphere having a radius equal to said operating wavelength
divided by two times .pi.. Therefore, a maximum size of the antenna
element must necessarily be not larger than the diameter of said
radiansphere (i.e., approximately equal to 1/3 of the free-space
operating wavelength) in order to be considered small at said given
operating wavelength.
[0055] As established theoretically by H. Wheeler and L. J. Chu in
the mid 1940's, small antenna elements typically have a high
quality factor (Q) which means that most of the power delivered to
the antenna element is stored in the vicinity of the antenna
element in the form of reactive energy rather than being radiated
into space. In other words, an antenna element having a maximum
size smaller than 1/3 of the free-space operating wavelength may be
regarded as radiating poorly by a skilled-in-the-art person.
[0056] The at least one radiation booster for a radiating structure
according to the present invention has a maximum size at least
smaller than 1/30 of the free-space wavelength corresponding to the
lowest frequency of the first frequency region of operation. That
is, said radiation booster fits in an imaginary sphere having a
diameter ten (10) times smaller than the diameter of a radiansphere
at said same operating wavelength.
[0057] Setting the dimensions of the radiation booster to such
small values is advantageous because the radiation booster
substantially behaves as a non-radiating element for all the
frequencies of the first frequency region, thus substantially
reducing the loss of energy into free space due to undesired
radiation effects of the radiation booster, and consequently
enhancing the transfer of energy between the radiation booster and
the ground plane layer. Therefore, the skilled-in-the-art person
could not possibly regard the radiation booster as being an antenna
element.
[0058] Said maximum size is preferably defined by the largest
dimension of a booster box that completely encloses said radiation
booster, and in which the radiation booster is inscribed.
[0059] More specifically, a booster box for a radiation booster is
defined as being the minimum-sized parallelepiped of square or
rectangular faces that completely encloses the radiation booster
and wherein each one of the faces of said minimum-sized
parallelepiped is tangent to at least a point of said radiation
booster. Moreover, each possible pair of faces of said minimum-size
parallelepiped sharing an edge forms an inner angle of
90.degree..
[0060] In some examples, one of the dimensions of a booster box can
be substantially smaller than any of the other two dimensions, or
even be close to zero. In such cases, said booster box collapses to
a practically two-dimensional entity. The term dimension preferably
refers to an edge between two faces of said parallelepiped.
[0061] Additionally, in some of these examples the at least one
radiation booster has a maximum size larger than 1/1400, 1/700,
1/350, 1/250, 1/180, 1/140 or 1/120 times the free-space wavelength
corresponding to the lowest frequency of said first frequency
region. Therefore, in some examples the at least one radiation
booster has a maximum size advantageously smaller than a first
fraction of the free-space wavelength corresponding to the lowest
frequency of the first frequency region but larger than a second
fraction of said free-space wavelength.
[0062] Setting the dimensions of the radiation booster to be above
some certain minimum value is advantageous to obtain a higher level
of the real part of the input impedance of the radiating structure
(measured at the internal port of the radiating structure when
disconnected from the radiofrequency system) and hence enhance the
transfer of energy between the radiation booster and the ground
plane layer.
[0063] In some other cases, preferably in combination with the
above feature of an upper bound for the maximum size of the
radiation booster although not always required, to reduce even
further the losses in the radiation booster due to residual
radiation effects, the radiation booster is designed so that the
radiating structure has a first resonance frequency (as measured at
the internal port of said radiating structure when disconnected
from the radiofrequency system) at a frequency much higher than the
frequencies of the first frequency region of operation. In some
examples, the radiation booster connected to said internal port has
a dimension substantially close to a quarter of the wavelength
corresponding to said first resonance frequency. In some examples,
the ratio between the first resonance frequency of the radiating
structure at its internal port when disconnected from the
radiofrequency system and the highest frequency of said first
frequency region is preferably larger than a certain minimum ratio.
Some possible minimum ratios are 3.0, 3.4, 3.8, 4.0, 4.2, 4.4, 4.6,
4.8, 5.0, 5.2, 5.4, 5.6, 5.8, 6.0, 6.2, 6.6 or 7.0.
[0064] In the context of this document, a resonance frequency of
the radiating structure preferably refers to a frequency at which
the input impedance of said radiating structure (as measured at its
internal port when disconnected from the radiofrequency system) has
an imaginary part equal to zero.
[0065] With such a small radiation booster, and with the radiating
structure including said radiation booster operating in a frequency
range much lower than said first resonance frequency, the input
impedance of the radiating structure (measured at its internal port
when the radiofrequency system is disconnected) features an
important reactive component (either capacitive or inductive)
within the range of frequencies of the first frequency region of
operation. That is, the input impedance of the radiating structure
at said internal port when disconnected from the radiofrequency
system has an imaginary part not equal to zero for any frequency of
the first frequency region.
[0066] In some examples the radiation booster is substantially
planar defining a two-dimensional structure, while in other cases
the radiation booster is a three-dimensional structure that
occupies a volume. In particular, in some examples, the smallest
dimension of a booster box is not smaller than a 70%, an 80% or
even a 90% of the largest dimension of said booster box, defining a
volumetric geometry. Radiation boosters having a volumetric
geometry may be advantageous to enhance the radioelectric
performance of the radiating structure, particularly in those cases
in which the maximum size of the radiation booster is very small
relative to the free-space wavelength corresponding to the lowest
frequency of the first frequency region.
[0067] Moreover, providing a radiation booster with a volumetric
geometry can be advantageous to reduce the other two dimensions of
its radiator box, leading to a very compact solution. Therefore, in
some examples in which the radiation booster has a volumetric
geometry, it is preferred to set a ratio between the first
resonance frequency of the radiating structure at its internal port
when disconnected from the radiofrequency system and the highest
frequency of the first frequency region above 4.8, or even above
5.4.
[0068] In a preferred embodiment, the radiation booster comprises a
conductive part. In some cases said conductive part may take the
form of, for instance but not limited to, a conducting strip
comprising one or more segments, a polygonal shape (including for
instance triangles, squares, rectangles, hexagons, or even circles
or ellipses as limit cases of polygons with a large number of
edges), a polyhedral shape comprising a plurality of faces
(including also cylinders or spheres as limit cases of polyhedrons
with a large number of faces), or a combination thereof.
[0069] In some examples, the conductive part of a radiation booster
may be a contacting means of a circuit component, such as for
example a pin, a soldering ball, or a soldering pad of an
integrated circuit package, or of a surface-mount technology (SMT)
electronic component.
[0070] In some examples, the connection point of a radiation
booster is advantageously located substantially close to an end, or
to a corner, of said conductive part.
[0071] In some examples, the conductive part is connected to the
ground plane layer, while in other examples said conductive part is
not connected to the ground plane layer. Connecting the conductive
part of the radiation booster to the ground plane layer lowers
effectively the real part of the input impedance of the radiating
structure at its internal port when disconnected from the
radiofrequency system, controlling thus the energy transfer between
the radiation booster and the ground plane layer.
[0072] In another preferred example, the radiation booster
comprises a gap (i.e., absence of conducting material) defined in
the ground plane layer. Said gap is delimited by one or more
segments defining a curve. The connection point of the radiation
booster is located at a first point along said curve. The
connection point of the ground plane layer is located at a second
point along said curve, said second point being different from said
first point.
[0073] In an example, said gap intersects the perimeter of the
ground plane layer. That is, the curve defined by the one or more
segments delimiting said gap is open. In another example, said gap
does not intersect the perimeter of the ground plane layer (i.e.,
the curve defined by the one or more segments delimiting said gap
is closed).
[0074] In a preferred example of the present invention, a major
portion of the at least one radiation booster (such as at least a
50%, or a 60%, or a 70%, or an 80% of the surface of said radiation
booster) is placed on one or more planes substantially parallel to
the ground plane layer. In the context of this document, two
surfaces are considered to be substantially parallel if the
smallest angle between a first line normal to one of the two
surfaces and a second line normal to the other of the two surfaces
is not larger than 30.degree., and preferably not larger than
20.degree., or even more preferably not larger than 10.degree..
[0075] In some examples, said one or more planes substantially
parallel to the ground plane layer and containing a major portion
of a radiation booster of the radiating structure are preferably at
a height with respect to said ground plane layer not larger than a
2% of the free-space wavelength corresponding to the lowest
frequency of the first frequency region of operation of the
radiating system. In some cases, said height is smaller than 7 mm,
preferably smaller than 5 mm, and more preferably smaller than 3
mm.
[0076] In some embodiments, the at least one radiation booster is
substantially coplanar to the ground plane layer. Furthermore, in
some cases the at least one radiation booster is advantageously
embedded in the same PCB as the one containing the ground plane
layer, which results in a radiating structure having a very low
profile.
[0077] In a preferred example the radiating structure is arranged
within the wireless handheld or portable device in such a manner
that there is no ground plane in the orthogonal projection of a
radiation booster onto the plane containing the ground plane layer.
In some examples there is some overlapping between the projection
of a radiation booster and the ground plane layer. In some
embodiments less than a 10%, a 20%, a 30%, a 40%, a 50%, a 60% or
even a 70% of the area of the projection of a radiation booster
overlaps the ground plane layer. Yet in some other examples, the
projection of a radiation booster onto the ground plane layer
completely overlaps the ground plane layer.
[0078] In some cases it is advantageous to protrude at least a
portion of the orthogonal projection of a radiation booster beyond
the ground plane layer, or alternatively remove ground plane from
at least a portion of the projection of a radiation booster, in
order to adjust the levels of impedance and to enhance the
impedance bandwidth of the radiating structure. This aspect is
particularly suitable for those examples when the volume for the
integration of the radiating structure has a small height, as it is
the case in particular for slim wireless handheld or portable
devices.
[0079] In some examples, a radiation booster is preferably located
substantially close to an edge of the ground plane layer,
preferably said edge being in common with a side of the ground
plane rectangle. In some examples, a radiation booster is more
preferably located substantially close to an end of said edge or to
the middle point of said edge.
[0080] In some embodiments said edge is preferably an edge of a
substantially rectangular or elongated ground plane layer.
[0081] In an example, the radiation booster is located preferably
substantially close to a short edge of the ground plane rectangle,
and more preferably substantially close to an end of said short
edge or to the middle point of said short edge. Such a placement
for the radiation booster with respect to the ground plane layer is
particularly advantageous when the radiating structure features at
its internal port, when the radiofrequency system is disconnected,
an input impedance having a capacitive component for the
frequencies of the first frequency region of operation.
[0082] In another example, the radiation booster is located
preferably substantially close to a long edge of the ground plane
rectangle, and more preferably substantially close to an end of
said long edge or to the middle point of said long edge. Such a
placement for the radiation booster is particularly advantageous
when the radiating structure features at its internal port, when
the radiofrequency system is disconnected, an input impedance
having an inductive component for the frequencies of said first
frequency region.
[0083] In some other examples, a radiation booster is
advantageously located substantially close to a corner of the
ground plane layer, preferably said corner being in common with a
corner of the ground plane rectangle.
[0084] In the context of this document, two points are
substantially close to each other if the distance between them is
less than 5% (more preferably less than 3%, 2%, 1% or 0.5%) of the
lowest frequency of operation of the radiating system. In the same
way, two linear dimensions are substantially close to each other if
they differ in less than 5% (more preferably less than 3%, 2%, 1%
or 0.5%) of said lowest frequency of operation.
[0085] In some examples, the connection point of the ground plane
layer is located advantageously close to the connection point of
the radiation booster in order to facilitate the interconnection of
the radiofrequency system with the radiating structure. Therefore,
those locations specified above as being preferred for the
placement of the radiation booster are also advantageous for the
location of the connection point of the ground plane layer.
Therefore, in some examples said connection point is located
substantially close to an edge of the ground plane layer,
preferably an edge in common with a side of the ground plane
rectangle, or substantially close to a corner of the ground plane
layer, preferably said corner being in common with a corner of the
ground plane rectangle. Such an election of the position of the
connection point of the ground plane layer may be advantageous to
provide a longer path to the electrical currents flowing on the
ground plane layer, lowering the frequency of the radiation mode of
the ground plane layer.
[0086] In some embodiments, the radiofrequency system comprises a
matching network that transforms the input impedance of the
radiating structure, providing impedance matching to the radiating
system in at least the first frequency region of operation of the
radiating system.
[0087] Said matching network can comprise a single stage or a
plurality of stages. In some examples, the matching network
comprises at least two, at least three, at least four, at least
five, at least six, at least seven, at least eight or more
stages.
[0088] A stage comprises one or more circuit components (such as
for example but not limited to inductors, capacitors, resistors,
jumpers, short-circuits, switches, delay lines, resonators, or
other reactive or resistive components). In some cases, a stage has
a substantially inductive behavior in the first frequency region of
operation of the radiating system, while another stage has a
substantially capacitive behavior in said first frequency region,
and yet a third one may have a substantially resistive behavior in
said first frequency region.
[0089] A stage can be connected in series or in parallel to other
stages and/or to at least one port of the radiofrequency
system.
[0090] In some examples, the matching network alternates stages
connected in series (i.e., cascaded) with stages connected in
parallel (i.e., shunted), forming a ladder structure. In some
cases, a matching network comprising two stages forms an L-shaped
structure (i.e., series-parallel or parallel-series). In some other
cases, a matching network comprising three stages forms either a
pi-shaped structure (i.e., parallel-series-parallel) or a T-shaped
structure (i.e., series-parallel-series).
[0091] In some examples, the matching network alternates stages
having a substantially inductive behavior, with stages having a
substantially capacitive behavior.
[0092] In an example, a stage may substantially behave as a
resonant circuit (such as, for instance, a parallel LC resonant
circuit or a series LC resonant circuit) in the first frequency
region of operation of the radiating system. The use of stages
having a resonant circuit behavior allows one part of the matching
network be effectively connected to another part of said matching
network for a given range of frequencies, and be effectively
disabled for another range of frequencies.
[0093] In an example, the matching network comprises at least one
active circuit component (such as for instance, but not limited to,
a transistor, a diode, a MEMS device, a relay, or an amplifier) in
at least one stage.
[0094] In some embodiments, the matching network preferably
includes a reactance cancellation circuit comprising one or more
stages, with one of said one or more stages being connected to the
first port of the radiofrequency system.
[0095] In the context of this document, reactance cancellation
preferably refers to compensating the imaginary part of the input
impedance at the internal port of the radiating structure when
disconnected from the radiofrequency system so that the input
impedance of the radiating system at its external port has an
imaginary part substantially close to zero for a frequency
preferably within the first frequency region. In some less
preferred examples, said frequency may also be higher than the
highest frequency of the first frequency region (although
preferably not higher than 1.1, 1.2, 1.3 or 1.4 times said highest
frequency) or lower than the lowest frequency of the first
frequency region (although preferably not lower than 0.9, 0.8 or
0.7 times said lowest frequency). Moreover, the imaginary part of
an impedance is considered to be substantially close to zero if it
is not larger (in absolute value) than 15 Ohms, and preferably not
larger than 10 Ohms, and more preferably not larger than 5
Ohms.
[0096] In a preferred embodiment, the radiating structure features
at its internal port when the radiofrequency system is disconnected
an input impedance having a capacitive component for the
frequencies of the first frequency region of operation. In that
embodiment, the reactance cancellation circuit comprises a first
stage having a substantially inductive behavior for all the
frequencies of the first frequency region of operation of the
radiating system. More preferably, said first stage comprises an
inductor. In some cases, said inductor may be a lumped inductor.
Said first stage is advantageously connected in series with the
first port of the radiofrequency system, said first port being
connected to the internal port of the radiating structure of a
radiating system.
[0097] In another preferred embodiment, the radiating structure
features at its internal port when the radiofrequency system is
disconnected an input impedance having an inductive component for
the frequencies of the first frequency region of operation. In that
embodiment, the reactance cancellation circuit comprises a first
stage and a second stage forming an L-shaped structure, with said
first stage being connected in parallel and said second stage being
connected in series. Each of the first and the second stage has a
substantially capacitive behavior for all the frequencies of the
first frequency region of operation of the radiating system. More
preferably, said first stage and said second stage comprise each a
capacitor. In some cases, said capacitor may be a lumped capacitor.
Said first stage is advantageously connected in parallel with the
first port of the radiofrequency system, while said second stage is
connected to said first stage.
[0098] In some embodiments, the matching network may further
comprise a broadband matching circuit, said broadband matching
circuit being preferably connected in cascade to the reactance
cancellation circuit. With a broadband matching circuit, the
impedance bandwidth of the radiating structure may be
advantageously increased. This may be particularly interesting for
those cases in which the relative bandwidth of the first frequency
region is large.
[0099] In a preferred embodiment, the broadband matching circuit
comprises a stage that substantially behaves as a resonant circuit
(preferably as a parallel LC resonant circuit or as a series LC
resonant circuit) in the first frequency region of operation of the
radiating system.
[0100] In some examples, the matching network may further comprise
in addition to the reactance cancellation circuit and/or the
broadband matching circuit, a fine tuning circuit (also called
third tuning circuit) to correct small deviations of the input
impedance of the radiating system with respect to some given target
specifications.
[0101] In a preferred example, the reactance cancellation circuit
is connected to the first port of the radiofrequency system (i.e.,
the port connected to the internal port of the radiating structure)
and the fine tuning circuit is connected to the second port of the
radiofrequency system (i.e., the port connected to the external
port of the radiating system). In an example, then the broadband
matching circuit is operationally connected in cascade between the
reactance cancellation circuit and the fine tuning circuit. In
another example, the matching network does not comprise a broadband
matching circuit and the reactance cancellation circuit is
connected in cascade directly to the fine tuning circuit.
[0102] In some examples, at least some circuit components in the
stages of the matching network are discrete lumped components (such
as for instance SMT components), while in some other examples all
the circuit components of the matching network are discrete lumped
components. In some examples, at least some circuit components in
the stages of the matching network are distributed components (such
as for instance a transmission line printed or embedded in a PCB
containing the ground plane layer of the radiating structure),
while in some other examples all the circuit components of the
matching network are distributed components.
[0103] In some examples, at least some, or even all, circuit
components in the stages of the matching network may be integrated
into an integrated circuit, such as for instance a CMOS integrated
circuit or a hybrid integrated circuit.
[0104] In some embodiments, the radiofrequency system may comprise
a frequency selective element such as a diplexer or a bank of
filters to separate the electrical signals of different
frequencies.
[0105] In some embodiments, the radiofrequency system includes two,
three, four or more matching networks and a switching matrix. The
switching matrix allows selecting which one of the two or more
matching networks is operationally connected to a port of the
radiofrequency system. In these embodiments, the radiofrequency
system further comprises a control circuit to select which matching
network is selected at any given time, hence providing
reconfiguration capabilities to the radiofrequency system.
[0106] In some preferred embodiments, the switching matrix is
advantageously connected to the first port of the radiofrequency
system (i.e., the port connected to internal port of the radiating
structure).
[0107] Moreover, in a more preferred embodiment the radiofrequency
system comprises a second switching matrix, said second switching
matrix being connected to the second port of the radiofrequency
system (i.e., the port connected to external port of the radiating
system).
[0108] A radiating system comprising such a reconfigurable
radiofrequency system may be advantageous to adapt the radiating
system to different working environments, or to different modes of
operation of the wireless device. It may also allow re-using a same
radiating system for different frequency regions that are not used
simultaneously. For example a same cellular communication standard
may be allocated in different frequency regions of the
electromagnetic spectrum depending on the geographical region. An
antennaless wireless handheld or portable device may advantageously
select the matching network optimized for instance to the frequency
region corresponding to a European standard, to an American
standard, or to an Asian standard depending on where the wireless
device is being used at any given moment.
[0109] In some examples, one, two, three or even all the stages of
the matching network may contribute to more than one functionality
of said matching network. A given stage may for instance contribute
to two or more of the following functionalities from the group
comprising: reactance cancellation, impedance transformation
(preferably, transformation of the real part of said impedance),
broadband matching and fine tuning matching. In other words, a same
stage of the matching network may advantageously belong to two or
three of the following circuits: reactance cancellation circuit,
broadband matching circuit and fine tuning circuit. Using a same
stage of the matching network for several purposes may be
advantageous in reducing the number of stages and/or circuit
components required for the matching network of a radiofrequency
system, reducing the real estate requirements on the PCB of the
antennaless wireless handheld or portable device in which the
radiating system is integrated.
[0110] In other examples, each stage of the matching network serves
only to one functionality within the matching network. Such a
choice may be preferred when low-end circuit components, having for
instance a worse tolerance behavior, a more pronounced thermal
dependence, and/or a lower quality factor, are used to implement
said matching network.
[0111] In some examples, the radiating system is capable of
operating in at least two, three, four, five or more frequency
regions of the electromagnetic spectrum, said frequency regions
allowing the allocation of two, three, four, five, six or more
frequency bands used in one or more standards of cellular
communications, wireless connectivity and/or broadcast
services.
[0112] In some examples, a frequency region of operation (such as
for example the first frequency region) of a radiating system is
preferably one of the following: 824-960 MHz, 1710-2170 MHz,
2.4-2.5 GHz, 3.4-3.6 GHz, 4.9-5.875 GHz, or 3.1-10.6 GHz.
[0113] In some embodiments, the radiating structure comprises two,
three, four or more radiation boosters, each of said radiation
boosters including a connection point, and each of said connection
points defining, together with a connection point of the ground
plane layer, an internal port of the radiating structure.
Therefore, in some embodiments the radiating structure comprises
two, three, four or more radiation boosters, and correspondingly
two, three, four or more internal ports. In such embodiments, the
radiofrequency system comprises additional ports to be connected to
some, or even all, internal ports of the radiating structure.
[0114] In some examples, a same connection point of the ground
plane layer is used to define at least two, or even all, internal
ports of the radiating structure.
[0115] In some examples, the radiating system comprises a second
external port and the radiofrequency system comprises an additional
port, said additional port being connected to said second external
port. That is, the radiating system features two external
ports.
[0116] In some embodiments the radiating structure comprises a
plastic or dielectric carrier (such as for instance made of Poly
Carbonate, Liquid Crystal Polymer, Poly Oxide Methylene, PC-ABS, or
PVC) that provides mechanical support to the at least one radiation
booster of said radiating structure. In other cases, the at least
one radiation booster is affixed to a plastic cover of the wireless
handheld or portable device.
[0117] In some embodiments a radiation booster may be
advantageously arranged in an integrated circuit package (i.e., a
package having a form factor for integrated circuit packages).
[0118] In some embodiments, said integrated circuit package
advantageously comprises a semiconductor chip or die arranged
inside the package. Moreover, the radiation booster is preferably
arranged in the package but not in said semiconductor die or
chip.
[0119] In some cases, the integrated circuit package has a form
factor selected from the list comprising: single-in-line (SIL)
package, dual-in-line (DIL) package, dual-in-line with surface
mount technology (DIL-SMT) package, quad-flat-package (QFP)
package, quad-flat-no-lead (QFN) package, pin grid array (PGA)
package, ball grid array (BGA) package, plastic ball grid array
(PBGA) package, ceramic ball grid array (CBGA) package, tape ball
grid array (TBGA) package, super ball grid array (SBGA) package,
micro ball grid array (.mu.BGA) package, small outline package and
leadframe package. Moreover, in some examples, any of these form
factors may be used in its CSP (Chip Scale Package) version,
wherein the semiconductor chip or die typically fills up to an 85%
of the package area.
[0120] The integrated circuit package further comprises at least
one terminal (such as for instance but not limited to a pad, a pin
or a lead) or, more preferably, a plurality of terminals.
[0121] In some preferred examples, the contact point of the
radiation booster is connected to a terminal of the integrated
circuit package. Moreover, in these examples the radiofrequency
system is at least in part not included in the integrated circuit
package. Having at least a part of the radiofrequency system
outside the integrated circuit package may offer to the user
greater flexibility in the customization of the matching network
and the selection of particular circuit components to obtain a
desired radioelectric performance of the radiating system.
[0122] In some cases according to the present invention, a terminal
of the integrated circuit package may constitute the conductive
part of the radiation booster.
[0123] In some examples, the connection point of the ground plane
layer of the radiating structure is connected to at least one
terminal of the integrated circuit package. In these examples, the
integrated circuit package includes at least part of the
radiofrequency system.
[0124] Having at least part of the radiofrequency system inside the
integrated circuit may enable the use of for instance active
circuit components, or have an adaptive matching network which can
be reconfigured to different working environments and conditions.
In these cases, the radiofrequency system may advantageously
further comprise a control circuit, preferably included in the
semiconductor chip or die, to configure such an adaptive matching
network.
BRIEF DESCRIPTION OF THE DRAWINGS
[0125] Embodiments of the invention are shown in the enclosed
figures. Herein shows:
[0126] FIGS. 1A, 1B--(FIG. 1A) Example of an antennaless wireless
handheld or portable device including a radiating system according
to the present invention; and (FIG. 1B) block diagram of an
antennaless wireless handheld or portable device illustrating the
basic functional blocks thereof.
[0127] FIG. 2--Schematic representation of a radiating system
according to the present invention.
[0128] FIGS. 3A, 3B, 3C--Block diagrams of three examples of
radiofrequency systems for a radiating system according to the
present invention.
[0129] FIGS. 4A, 4B--Example of a radiating structure for a
radiating system, the radiating structure including a radiation
booster comprising a conductive part: (FIG. 4A) Partial perspective
view; and (FIG. 4B) top plan view.
[0130] FIG. 5--Schematic representation of a radiofrequency system
for a radiating system whose radiating structure is shown in FIGS.
4A and 4B.
[0131] FIGS. 6A, 6B, 6C--Typical impedance transformation of the
radiofrequency system of FIG. 5 on the input impedance of the
radiating structure of FIGS. 4A and 4B: (FIG. 6A) Input impedance
at the internal port of the radiating structure when disconnected
from the radiofrequency system; (FIG. 6B) Input impedance after
connection of the reactance cancellation circuit of the
radiofrequency system to the internal port of the radiating
structure; and (FIG. 6C) Input impedance at the external port of
the radiating system after connection of the broadband matching
circuit in cascade with the reactance cancellation circuit.
[0132] FIG. 7--Typical input return losses at the internal port of
the radiating structure of FIGS. 4A-4B compared with those at the
external port of a radiating system obtained after interconnecting
the radiating structure of FIGS. 4A-4B with the radiofrequency
system of FIG. 5.
[0133] FIGS. 8A, 8B--Another example of a radiating structure
including a radiation booster comprising a conductive part: (FIG.
8A) Partial perspective view; and (FIG. 8B) top plan view.
[0134] FIG. 9--Schematic representation of a radiofrequency system
for a radiating system whose radiating structure is shown in FIGS.
8A-8B.
[0135] FIGS. 10A, 10B--Typical impedance transformation of the
radiofrequency system of FIG. 9 on the input impedance of the
radiating structure of FIGS. 8A-8B: (FIG. 10A) Input impedance at
the internal port of the radiating structure when disconnected from
the radiofrequency system; and (FIG. 10B) Input impedance at the
external port of the radiating system.
[0136] FIG. 11--Typical input return losses at the internal port of
the radiating structure of FIGS. 8A and 8B compared with those at
the external port of a radiating system obtained after
interconnecting the radiating structure of FIGS. 8A and 8B with the
radiofrequency system of FIG. 9.
[0137] FIGS. 12A, 12B--Example of a radiating structure for a
radiating system, the radiating structure including a radiation
booster comprising a gap: (FIG. 12A) Partial perspective view; and
(FIG. 12B) top plan view.
[0138] FIG. 13--Schematic representation of a radiofrequency system
for a radiating system whose radiating structure is shown in FIGS.
12A-12B.
[0139] FIG. 14A-14D--Typical impedance transformation of the
radiofrequency system of FIG. 13 on the input impedance of the
radiating structure of FIGS. 12A-12B: (FIG. 4A) Input impedance at
the internal port of the radiating structure when disconnected from
the radiofrequency system; (FIG. 14B) Input impedance after
connection of the reactance cancellation circuit of the
radiofrequency system to the internal port of the radiating
structure; (FIG. 14C) Input impedance after connection of the
broadband matching circuit in cascade with the reactance
cancellation circuit; and (FIG. 14D) Input impedance at the
external port of the radiating system after connection of the fine
tuning circuit in cascade with the broadband matching circuit.
[0140] FIG. 15--Typical input return losses at the internal port of
the radiating structure of FIGS. 12A-12B compared with those at the
external port of a radiating system obtained after interconnecting
the radiating structure of FIG. 13 with the radiofrequency system
of FIGS. 12A-12B.
[0141] FIGS. 16A, 16B, 16C--Examples of radiation boosters
comprising a conductive part.
[0142] FIGS. 17A-17E--Examples of some preferred placements of the
radiation boosters of FIGS. 16A-16C with respect to the ground
plane layer of a radiating structure.
[0143] FIG. 18--Another example of a radiation booster comprising a
conductive part, wherein said conductive part is connected to the
ground plane layer of a radiating structure.
[0144] FIGS. 19A-19E--Examples of some preferred placements of the
radiation booster of FIG. 18 with respect to the ground plane layer
of a radiating structure.
[0145] FIGS. 20A, 20B--Examples of radiation boosters comprising a
gap.
[0146] FIGS. 21A-21D--Examples of some preferred placements of the
radiation boosters of FIGS. 20A and 20B with respect to the ground
plane layer of a radiating structure.
[0147] FIG. 22--Example of a preferred radiating structure
including a radiation booster comprising a gap.
[0148] FIGS. 23A, 23B--(FIG. 23A) Example of another preferred
radiating structure including a radiation booster comprising a gap;
and (FIG. 23B) Detailed view of the radiation booster.
[0149] FIG. 24--Further example of a preferred radiating structure
including a radiation booster comprising a gap.
[0150] FIG. 25--Example of a preferred radiating structure
including a radiation booster having a substantially planar
conductive part.
[0151] FIG. 26--Example of a reconfigurable radiofrequency system
for a radiating system comprising a controllable switching matrix
and a control circuit.
[0152] FIG. 27--Another example of a reconfigurable radiofrequency
system for a radiating system comprising two controllable switching
matrices and a control circuit.
[0153] FIG. 28--Radiating structure of a typical wireless handheld
or portable device.
DETAILED DESCRIPTION
[0154] Further characteristics and advantages of the invention will
become apparent in view of the detailed description of some
preferred embodiments which follows. Said detailed description of
some preferred embodiments of the invention is given for purposes
of illustration only and in no way is meant as a definition of the
limits of the invention, made with reference to the accompanying
figures.
[0155] FIGS. 1A-1B show an illustrative example of an antennaless
wireless handheld or portable device 100 according to the present
invention. In FIG. 1A, there is shown an exploded perspective view
of the antennaless wireless handheld or portable device 100
comprising a radiating structure that includes a radiation booster
151 and a ground plane layer 152 (which could be included in a
layer of a multilayer PCB). The antennaless wireless handheld or
portable device 100 also comprises a radiofrequency system 153,
which is interconnected with said radiating structure.
[0156] Referring now to FIG. 1B, it is shown a block diagram of the
antennaless wireless handheld or portable device 100 advantageously
comprising, in accordance to the present invention, a user
interface module 101, a processing module 102, a memory module 103,
a communication module 104 and a power management module 105. In a
preferred embodiment, the processing module 102 and the memory
module 103 have herein been listed as separate modules. However, in
another embodiment, the processing module 102 and the memory module
103 may be separate functionalities within a single module or a
plurality of modules. In a further embodiment, two or more of the
five functional blocks of the antennaless wireless handheld or
portable device 100 may be separate functionalities within a single
module or a plurality of modules.
[0157] In FIG. 2 it is depicted a radiating system 200 for an
antennaless wireless handheld or portable device according to the
present invention. The radiating system 200 comprises a radiating
structure 201, a radiofrequency system 202, and an external port
203. The radiating structure 201 comprises a radiation booster 204,
which includes a connection point 205, and a ground plane layer
206, said ground plane layer also including a connection point 207.
The radiating structure 201 further comprises an internal port 208
defined between the connection point of the radiation booster 205
and the connection point of the ground plane layer 207.
Furthermore, the radiofrequency system 202 comprises two ports: a
first port 209 is connected to the internal port of the radiating
structure 208, and a second port 210 is connected to the external
port of the radiating system 203.
[0158] FIG. 3A-3C show the block diagrams of three preferred
examples of a radio frequency system 300 comprising a first port
301 and a second port 302.
[0159] In particular, in FIG. 3A the radiofrequency system 300
includes matching network comprising a reactance cancellation
circuit 303. In this example, a first port of the reactance
cancellation circuit 304 may be operationally connected to the
first port of the radiofrequency system 301 and another port of the
reactance cancellation circuit 305 may be operationally connected
to the second port of the radiofrequency system 302.
[0160] Referring now to FIG. 3B, the radiofrequency system 300
includes an alternative matching network comprising the reactance
cancellation circuit 303 and a broadband matching circuit 330,
which is advantageously connected in cascade with the reactance
cancellation circuit 303. That is, a port of the broadband matching
circuit 331 is connected to port 305. In this example, port 304 is
operationally connected to the first port of the radiofrequency
system 301, while another port of the broadband matching circuit
332 is operationally connected to the second port of the
radiofrequency system 302.
[0161] FIG. 3C depicts a further example of the radiofrequency
system 300 including yet another alternative matching network
comprising, in addition to the reactance cancellation circuit 303
and the broadband matching circuit 330, a fine tuning circuit 360.
Said three circuits are advantageously connected in cascade, with a
port of the reactance cancellation circuit (in particular port 304)
being connected to the first port of the radiofrequency system 301
and a port the fine tuning circuit 362 being connected to the
second port of the radiofrequency system 302. In this example, the
broadband matching circuit 330 is operationally interconnected
between the reactance cancellation circuit 303 and the fine tuning
circuit 360 (i.e., port 331 is connected to port 305 and port 332
is connected to port 361 of the fine tuning circuit 360).
[0162] FIGS. 4A-4B show a preferred example of a radiating
structure suitable for a radiating system operating in a first
frequency region of the electromagnetic spectrum between 824 MHz
and 960 MHz. An antennaless wireless handheld or portable device
including such a radiating system may advantageously operate the
GSM 850 and GSM 900 cellular communication standards (i.e., two
different communication standards).
[0163] The radiating structure 400 comprises a radiation booster
401 and a ground plane layer 402. In FIG. 4B, there is shown in a
top plan view the ground plane rectangle 450 associated to the
ground plane layer 402. In this example, since the ground plane
layer 402 has a substantially rectangular shape, its ground plane
rectangle 450 is readily obtained as the rectangular perimeter of
said ground plane layer 402.
[0164] The ground plane rectangle 450 has a long side of
approximately 100 mm and a short side of approximately 40 mm.
Therefore, in accordance with an aspect of the present invention,
the ratio between the long side of the ground plane rectangle 450
and the free-space wavelength corresponding to the lowest frequency
of the first frequency region (i.e., 824 MHz) is advantageously
larger than 0.2. Moreover, said ratio is advantageously also
smaller than 1.0.
[0165] In this example, the radiation booster 401 includes a
conductive part featuring a polyhedral shape comprising six faces.
Moreover, in this case said six faces are substantially square
having an edge length of approximately 5 mm, which means that said
conductive part is a cube. In this case, the conductive part of the
radiation booster 401 is not connected to the ground plane layer
402. A booster box 451 for the radiation booster 401 coincides with
the external area of said radiation booster 401. In FIG. 4B, it is
shown a top plan view of the radiating structure 400, in which the
top face of the booster box 451 can be observed.
[0166] In accordance with an aspect of the present invention, a
maximum size of the radiation booster 401 (said maximum size being
a largest edge of the booster box 451) is advantageously smaller
than 1/50 times the free-space wavelength corresponding to the
lowest frequency of the first frequency region of operation of the
radiating structure 400. In particular, said maximum size is also
advantageously larger than 1/180 times said free-space
wavelength.
[0167] In FIGS. 4A-4B, the radiation booster 401 is arranged with
respect to the ground plane layer so that the upper and bottom
faces of the radiation booster 401 are substantially parallel to
the ground plane layer 402. Moreover, said bottom face is
advantageously coplanar to the ground plane layer 402. With such an
arrangement, the height of the radiation booster 401 with respect
to the ground plane layer is not larger than 2% of the free-space
wavelength corresponding to the lowest frequency of the first
frequency region.
[0168] In the radiating structure 400, the radiation booster 401
protrudes beyond the ground plane layer 402. That is, the radiation
booster 401 is arranged with respect to the ground plane layer 402
in such a manner that there is no ground plane in the orthogonal
projection of the radiation booster 401 onto the plane containing
the ground plane layer 402. The radiation booster 401 is located
substantially close to an edge of the ground plane layer 402, in
particular to a short edge of the substantially rectangular ground
plane layer 402 and, more precisely, the radiation booster 401 is
located substantially close to a corner of said ground plane layer
402.
[0169] The radiation booster 401 comprises a connection point 403
located on the lower right corner of the bottom face of the
radiation booster 401. In turn, the ground plane layer 402 also
comprises a connection point 404 substantially on the upper right
corner of the ground plane layer 402. An internal port of the
radiating structure 400 is defined between connection point 403 and
connection point 404.
[0170] The very small dimensions of the radiation booster 401
result in said radiating structure 400 having a first resonance
frequency at a frequency much higher than the frequencies of the
first frequency region. In this case, the ratio between the first
resonance frequency of the radiating structure 400 measured at its
internal port (in absence of a radiofrequency system connected to
it) and the highest frequency of the first frequency region is
advantageously larger than 4.2.
[0171] With such small dimensions of the radiation booster 401, the
input impedance of the radiating structure 400 measured at the
internal port features an important reactive component, and in
particular a capacitive component, within the frequencies of the
first frequency region.
[0172] This can be observed in FIG. 6A, in which curve 600
represents on a Smith chart the typical complex impedance of the
antenna structure 400 as a function of the frequency when no
radiofrequency system is connected to its internal port. In
particular, point 601 corresponds to the input impedance at the
lowest frequency of the first frequency region, and point 602
corresponds to the input impedance at the highest frequency of the
first frequency region.
[0173] Curve 600 is located on the lower half of the Smith chart,
which indeed indicates that said input impedance has a capacitive
component (i.e., the imaginary part of the input impedance has a
negative value) for all frequencies of the first frequency range
(i.e., between point 601 and point 602).
[0174] FIG. 5 is a schematic representation of a radiofrequency
system suitable for interconnection with the radiating structure of
FIGS. 4A-4B to provide impedance matching to the resulting
radiating system in the first frequency region of operation.
[0175] A radiofrequency system 500 comprises a first port 501 to be
connected to the internal port of the radiating structure 400, and
a second port 502 to be connected to the external port of the
radiating system. In this example, the radiofrequency system 500
further comprises a matching network including a reactance
cancellation circuit 507 and a broadband matching circuit 508.
[0176] The reactance cancellation circuit 507 includes one stage
comprising one single circuit component 504 arranged in series and
featuring a substantially inductive behavior in the first frequency
region. In this particular example, the circuit component 504 is a
lumped inductor. The inductive behavior of the reactance
cancellation circuit 507 advantageously compensates the capacitive
component of the input impedance of the radiating structure
400.
[0177] Such an effect can be observed in FIGS. 6A-6C, in which the
input impedance of the radiating structure 400 (curve 600 in FIG.
6A) is transformed by the reactance cancellation circuit into an
impedance having an imaginary part substantially close to zero in
the first frequency region (see FIG. 6B). Curve 630 in FIG. 6B
corresponds to the input impedance that would be observed at the
second port of the radiofrequency system 502 if the broadband
matching circuit 508 were removed and said second port 502 were
directly connected to a port 503. Said curve 630 crosses the
horizontal axis of the Smith Chart at a point 631 located between
point 601 and point 602, which means that the input impedance has
an imaginary part equal to zero for a frequency advantageously
between the lowest and highest frequencies of the first frequency
region.
[0178] The broadband matching circuit 508 includes also one stage
and is connected in cascade with the reactance cancellation circuit
507. Said stage of the broadband matching circuit 508 comprises two
circuit components: a first circuit component 505 is a lumped
inductor and a second circuit component 506 is a lumped capacitor.
Together, the circuit components 505 and 506 form a parallel LC
resonant circuit (i.e., said stage of the broadband matching
circuit 508 behaves substantially as a resonant circuit in the
first frequency region of operation).
[0179] Comparing FIGS. 6B and 6C, it is noticed that the broadband
matching circuit 508 has the beneficial effect of "closing in" the
ends of curve 630 (i.e., transforming the curve 630 into another
curve 660 featuring a compact loop around the center of the Smith
chart). Thus, the resulting curve 660 exhibits an input impedance
(now, measured at the second port 502, or equivalently at the
external port of the radiating system) within a voltage standing
wave ratio (VSWR) 3:1 referred to a reference impedance of 50 Ohms
over a broader range of frequencies.
[0180] Alternatively, the effect of the radiofrequency system of
FIG. 5 on the radiating structure of FIGS. 4A-4B can be compared in
terms of the input return loss. In FIG. 7 curve 700 (in dash-dotted
line) presents the typical input return loss of the radiating
structure 400 observed at its internal port when the radiofrequency
system 500 is not connected to said internal port. From said curve
700 it is clear that the radiating structure 400 is not matched in
the first frequency range and that the radiation booster 401 is
non-resonant in said first frequency range. On the other hand,
curve 710 (in solid line) corresponds to the input return losses at
the external port of the radiating system resulting from the
interconnection of the radiofrequency system 500 with the radiating
structure 400. The radiofrequency system transforms the input
impedance of the radiating structure 400, providing impedance
matching in the first frequency region. Curve 710 shows how the
radiating system exhibits return losses better than -6 dB in the
first frequency region (delimited by points 701 and 702 on the
curve 710), making it possible for the radiating system to provide
operability for the GSM850 and the GSM900 standards.
[0181] Another preferred embodiment of a radiating structure
according to the present invention is disclosed in FIGS. 8A-8B, in
which a radiating structure 800 comprises a radiation booster 801
and a ground plane layer 802. The radiating structure 800 is to be
used in a radiating system capable of operating the GSM 900
cellular communication standard (i.e., the first frequency region
extends from 880 MHz to 960 MHz).
[0182] The radiating structure 800 is very similar to the radiating
structure 400 already discussed in connection with FIGS. 4A-4B. For
example, the dimensions of the ground plane layer 802, and the
shape and dimensions of the radiation booster 801, are the same as
those of their respective counterparts in the radiating structure
400. Moreover, a ground plane rectangle 850 associated to the
ground plane layer 802 and a booster box 851 associated to the
radiation booster 801 are defined in the same way as it was done
for the example in FIGS. 4A-4B.
[0183] However, the placement of the radiation booster 801 with
respect to the ground plane layer 802 is different from what it was
shown in FIGS. 4A-4B. While in the radiating structure 400, the
radiation booster 401 protrudes beyond the ground plane layer 402;
in the radiating structure 800, the projection of the radiation
booster 801 onto the plane containing the ground plane layer 802
overlaps completely the ground plane layer 802. This can be
observed in the top plan view of the radiating structure 800 in
FIG. 8B, in which the projection of the booster box 851 onto the
plane of the ground plane layer 802 is inside the ground plane
rectangle 851.
[0184] Despite the radiation booster 801 being located above the
ground plane layer 802, said radiation booster 801 is not connected
to said ground plane layer 802. An internal port of the radiating
structure 800 is defined between a connection point of the
radiation booster 801 and a connection point of the ground plane
layer 802.
[0185] Referring now to FIG. 9, it is depicted a schematic
representation of a radiofrequency system 900 suitable for
interconnection with the radiating structure 800. The
radiofrequency system 900 includes a matching network, a first port
901 (to be connected to the internal port of the radiating
structure 800), and a second port 902 (for connection with the
external port of a resulting radiating system). The matching
network comprises a reactance cancellation circuit 910 and a
broadband matching circuit 911, as in the example shown in FIG. 5,
but also a fine tuning circuit 912.
[0186] The reactance cancellation circuit 910 is connected to the
first port 901 and the fine tuning circuit 912 is connected to the
second port 902. The broadband matching circuit 911 is
operationally connected between the reactance cancellation circuit
910 and the fine tuning circuit 912, so that said three circuits
are connected in cascade.
[0187] The input impedance of the radiating structure 800 measured
at its internal port (in absence of the radiofrequency system 900)
has an imaginary part featuring an important capacitive component.
In FIG. 10A said input impedance is represented by curve 1000,
which is clearly located in the lower half portion of the Smith
chart for all frequencies of the first frequency region
(represented by the interval between point 1001 and point 1002 of
the curve 1000). Therefore the reactance cancellation circuit 910
comprises a circuit element 903 having a substantially inductive
behavior (in particular being a lumped inductor).
[0188] The broadband matching circuit 911 is similar to the one
used for the radiofrequency system 500, and includes one stage
substantially behaving as an LC parallel resonant circuit
comprising an inductor 904 and a capacitor 905 connected in
parallel.
[0189] The fine tuning circuit 912 adds two more stages to the
matching network of the radiofrequency system 900. Said two stages
form an L-shaped structure having a series inductor 906 and a
parallel capacitor 907. In this particular example, the fine tuning
circuit 912 provides an additional transformation of the impedance,
necessary to attain the required level of impedance matching in the
first frequency region.
[0190] FIG. 10B shows the effect of the radiofrequency system 900
on the input impedance of the radiating structure 800, in which
curve 1050 correspond to the input impedance observed at an
external port of the radiating system obtained from the
interconnection of radiating structure 800 and radiofrequency
system 900. Thanks to the contributions of the reactance
cancellation circuit 910, the broadband matching circuit 911 and
the fine tuning circuit 912, the curve 1000 transforms into the
curve 1050 which features a loop around the center of the Smith
chart.
[0191] The same typical results are shown in FIG. 11 in terms of
input return losses. The radiofrequency system 900 transforms curve
1100 (in dash-dotted line), corresponding to the input return loss
of the radiating structure 800 observed at its internal port when
the radiofrequency system 900 is not connected to said internal
port, into curve 1110 (in solid line), corresponding to the input
return losses at the external port of the radiating system
resulting from the interconnection of said radiofrequency system
900 with the radiating structure 800. Said curve 1110 feature a
return loss better than -4 dB for all frequencies of the first
frequency region (delimited by points 1101 and 1102 on the curve
1110).
[0192] FIGS. 12A-12B show another preferred example of a radiating
structure suitable for a radiating system operating in a first
frequency region of the electromagnetic spectrum between 923 MHz
and 969 MHz.
[0193] The radiating structure 1200 comprises a radiation booster
2000 and a ground plane layer 2010, having a substantially
rectangular shape. In FIG. 12B, it is shown the ground plane
rectangle 1250 associated to the ground plane layer 2010, which in
this example corresponds to the rectangular perimeter of said
ground plane layer 2010. The ground plane rectangle 1250 has a long
side and a short side and, in accordance with the present
invention, the ratio between said long side and the free-space
wavelength corresponding to the lowest frequency of the first
frequency region is advantageously larger than 0.16. Moreover, said
ratio is advantageously also smaller than 1.2.
[0194] In this example, the radiation booster 2000 comprises a gap
defined in the ground plane layer 2010. A closer view of said
radiation booster 2000 is provided in FIG. 20A. Said gap of the
radiation booster 2000 has a polygonal shape delimited by a
plurality of segments (segments 2001, 2002 and 2003) defining a
curve. A connection point of the radiation booster 2004 is located
at a first point along said curve (in particular a point on segment
2003), while a connection point of the ground plane layer 2011 is
located at a second point along said curve (in particular a point
on segment 2001). In some examples, according to the present
invention, as in this particular example, the connection point of
the radiation booster 2004 and the connection point of the ground
plane layer 2011 are located on two segments that are at opposite
sides of the gap of the radiation booster 2000. An internal port of
the radiating structure 1200 is consequently defined between the
connection point of the radiation booster 2004 and the connection
point of the ground plane layer 2011.
[0195] In this example said gap intersects the perimeter of the
ground plane layer, which means that the curve delimiting said gap
is open. As it can be seen in FIG. 20A segments 2001 and 2003
intersect the perimeter of the ground plane layer 2010.
[0196] The use of the radiation booster 2000 in the radiation
structure 1200 results in a advantageously planar solution,
simplifying its integration in a wireless handheld or portable
device. In this example, a booster box 1251 for the radiation
booster 2000 is substantially planar (i.e., one of its dimensions
is substantially close to zero). Furthermore, since the gap of the
radiation booster 2000 has a substantially square shape, the
booster box 1251 contains the segments 2001, 2002 and 2003.
[0197] In accordance with an aspect of the present invention, a
maximum size of the radiation booster 2000 (said maximum size being
a largest edge of the booster box 1251) is advantageously smaller
than 1/40 times the free-space wavelength corresponding to the
lowest frequency of the first frequency region of operation of
radiating structure 1200. Additionally, in this example said
maximum size is also advantageously larger than 1/250 times said
free-space wavelength.
[0198] With such small dimensions of the radiation booster 2000,
the radiating structure 1200 features a first resonance frequency
at a frequency much higher than the frequencies of the first
frequency region and, in consequence, the input impedance of the
radiating structure 1200 measured at its internal port (in absence
of a radiofrequency system connected to it) has an important
reactive component, in particular an inductive component, within
the frequencies of said first frequency region. In this case, the
ratio between the first resonance frequency of the radiating
structure 1200 measured at its internal port (in absence of a
radiofrequency system connected to it) and the highest frequency of
the first frequency region is advantageously larger than 5.0.
[0199] In the radiating structure 1200, the radiation booster 2000
is located with respect to the ground plane layer 2010 in such a
manner that the gap of the radiation booster 2000 intersects an
edge of the ground plane layer 2010, in particular a long edge of a
substantially rectangular ground plane layer 2010. More precisely,
the radiation booster 2000 is located substantially close to the
middle point of said long edge.
[0200] FIG. 13 depicts a schematic representation of a
radiofrequency system 1300 suitable for interconnection with the
radiating structure 1200. The radiofrequency system 1300 includes a
matching network, a first port 1301 (to be connected to the
internal port of the radiating structure 1200), and a second port
1302 (for connection with the external port of a resulting
radiating system). In this example, the matching network comprises
a reactance cancellation circuit 1310, a broadband matching circuit
1311, and a fine tuning circuit 1312 connected in cascade.
[0201] The input impedance of the radiating structure 1200 measured
at its internal port (in absence of the radiofrequency system 1300)
has an imaginary part featuring a significant inductive component,
as it can be seen in FIG. 14A. Said input impedance is represented
by curve 1400, which is located in the upper half portion of the
Smith chart for all frequencies of the first frequency region
(represented by the interval between point 1401 and point 1402 of
the curve 1400).
[0202] The reactance cancellation circuit 1310 is connected to the
first port 1301 and comprises two stages having a substantially
capacitive behavior and forming an L-shaped structure with a
parallel capacitor 1303 and a series capacitor 1304. The capacitive
behavior of the reactance cancellation circuit 1310 advantageously
compensates the inductive component of the input impedance of the
radiating structure 1200, transforming curve 1400 (FIG. 14A) into
curve 1420 (FIG. 14B). Said curve 1420 corresponds to the input
impedance that would be observed at the second port 1302 if the
broadband matching circuit 1311 and the fine tuning circuit 1312
were removed and said second port 1302 were directly connected to a
port 1320. In effect, the curve 1420 crosses the horizontal axis of
the Smith Chart (i.e., imaginary part of the input impedance equal
to zero) at a point 1421 located between point 1401 and point
1402.
[0203] The broadband matching circuit 1311 is connected in cascade
after the reactance cancellation circuit 1310 and is similar in
topology to the ones already discussed in connection with FIG. 5
and FIG. 9. Again, the broadband matching circuit 1311 includes one
stage substantially behaving as an LC parallel resonant circuit
comprising a capacitor 1305 and an inductor 1306 connected in
parallel.
[0204] The broadband matching circuit 1311 further transforms the
input impedance of the antenna structure and converts curve 1420
into curve 1440, said curve 1440 being the input impedance that
would be observed at the second port 1302 if the fine tuning
circuit 1312 were removed and said second port 1302 were directly
connected to a port 1321. Curve 1440 features a compact loop that
unfortunately is shifted towards the upper half of the Smith chart.
If said loop were centered on the center of the Smith chart,
impedance matching would be obtained over a much broader range of
frequencies.
[0205] Finally, the fine tuning circuit 1312 is connected in
cascade between the broadband matching circuit 1311 and the second
port 1302, and includes one stage having a substantially capacitive
behavior for all frequencies of the first frequency region. In
particular said stage comprises a series circuit element (lumped
capacitor 1307). The fine tuning circuit 1312 provides the
additional transformation of the input impedance necessary to
re-center the loop of curve 1440 on the center of the Smith chart.
In FIG. 14D, curve 1460 represents the input impedance measured at
the second port 1402, or equivalently at the external port of the
radiating system. Said curve 1460 attains the level of VSWR
required to provide operability to the radiating system in its
first frequency region.
[0206] Referring now to FIG. 15, it is shown there a comparison
between the typical input return losses observed at the internal
port of the radiating structure 1200 when the radiofrequency system
1300 is disconnected (see curve 1500 in dash-dotted line) and the
typical input return losses at the external port of the radiating
system resulting from the interconnection of said radiofrequency
system 1300 with the radiating structure 1200 (see curve 1510 in
solid line). The presence of radiofrequency system 1300 improves
substantially the return losses of the radiating structure 1200 for
all frequencies of the first frequency region (delimited in the
figure by points 1501 and 1502 on the curve 1510).
[0207] FIGS. 16A-16C show three preferred examples of radiation
boosters comprising a conductive part. Each of the radiation
boosters 1600, 1630, 1660 may advantageously excite a radiation
mode on a ground plane layer 1610. In these examples, the radiation
boosters 1600, 1630, 1660 are preferably not connected to the
ground plane layer 1610.
[0208] FIG. 16A depicts a radiation booster 1600 including a
conductive part featuring a polyhedral shape comprising a plurality
of faces. More precisely, said conductive part takes the shape of a
cube having six substantially square faces. Nevertheless, other
polyhedral shapes are also possible.
[0209] In this particular example, two of the faces of the
radiation booster (namely, the top face 1601 and the bottom face
1602) are substantially parallel to the ground plane layer 1610,
which may facilitate the integration of the radiation booster 1600
into a wireless handheld or portable device by mounting said
radiation booster 1600 on a PCB of the wireless device, and in
particular the PCB that also comprises the ground plane layer 1610.
However, in other examples, the radiation booster 1600 may not be
substantially parallel to the ground plane layer 1610.
[0210] In this case, a booster box associated to said radiation
booster 1600 coincides with the external surface of the radiation
booster 1600. Since the smallest dimension of said booster box is
not smaller than the 90% of the largest dimension of said booster
box, the radiation booster 1600 takes full advantage of being a
three-dimensional structure that occupies a volume.
[0211] The radiation booster 1600 also comprises a connection point
1603 advantageously located substantially close to a corner of the
radiation booster 1600, said corner being in particular also a
corner of the bottom face 1602. Said connection point 1603 defines
together with a connection point of the ground plane layer 1611 an
internal port of a radiating structure.
[0212] FIG. 16B shows radiation booster 1630 that includes a
conductive part also featuring a polyhedral shape. In this example,
said conductive part takes the form of a parallelepiped having
substantially a square top face, a bottom face and four
substantially rectangular lateral faces. However, other shapes for
the top and bottom faces are also possible (such as for instance,
but not limited to, triangle, pentagon, hexagon, octagon, circle,
or ellipse) and/or for the lateral faces. Furthermore, the
conductive part of the radiation booster could also have been
shaped as a cylinder having circular or elliptical top and bottom
faces. The conductive part of the radiation booster 1630 is mounted
with respect to the ground plane layer in such a way that the top
and bottom faces of the conductive part of said radiation booster
1630 are substantially parallel to the ground plane layer 1610.
[0213] As in the example of FIG. 16A, a booster box associated to
the radiation booster 1630 also coincides with the external surface
of the radiation booster 1630. However in the case of FIG. 16B, the
smallest dimension of the booster box associated to the radiation
booster 1630 is much smaller than the 70% of the largest dimension
of said booster box. Therefore, although the radiation booster 1630
is not planar (i.e., two dimensional), it does not take full
advantage of being a three-dimensional structure either.
[0214] The radiation booster 1630 further comprises a connection
point 1631, located substantially close to a corner of the
radiation booster 1630, which defines together with the connection
point of the ground plane layer 1611 an internal port of a
radiating structure.
[0215] In FIG. 16C it is shown a radiation booster 1660 including
also a conductive part. Said conductive part comprises a conductive
polygonal shape 1661 being substantially square and arranged
substantially parallel to the ground plane layer 1610 at a
predetermined height with respect said ground plane layer 1610. In
other examples, the conductive polygonal shape 1661 may be shaped
differently (for instance, as a polygon having a different number
of sides of the same or different lengths, or as a circle or an
ellipse).
[0216] Said conductive part further comprises a conductive strip
1662 having a substantially elongated shape and featuring two ends:
A first end of the conductive strip 1662 is connected to the
conductive polygonal shape 1661; and a second end of the conductive
strip 1662 includes a connection point 1663, which together with
the connection point of the ground plane layer 1611 defines an
internal port of a radiating structure. In this example, the
conductive strip 1662 is arranged substantially perpendicular to
the ground plane layer 1610.
[0217] A radiating structure resulting from the combination of any
of the radiation boosters 1600, 1630, 1660 in FIGS. 16A-16C with
the ground plane layer 1610, features an input impedance (measured
at the internal port of the radiating structure in absence of
radiofrequency system) having an imaginary part with an important
capacitive component. Therefore, such radiating structure could be
advantageously interconnected with a radiofrequency system such as
those in FIG. 5 or FIG. 9.
[0218] Referring now to FIGS. 17A-17E, it is shown some preferred
placements of the radiation boosters of FIGS. 16A-16C with respect
to a ground plane layer of a radiating structure.
[0219] In particular, FIG. 17A presents a radiating structure 1700
comprising the radiation booster 1660 and the ground plane layer
1610. The ground plane layer 1610 features a substantially
rectangular shape having a long edge 1701 and a short edge 1702. In
this example, the radiation booster 1660 is arranged substantially
centered with respect to the ground plane layer 1610. That is, the
radiation booster 1660 is substantially close to the point of the
ground plane layer 1610 defined by the intersection of a first line
1703 (perpendicular to the long edge 1701 and crossing said long
edge 1701 at its middle point) and a second line 1704
(perpendicular to the short edge 1702 and crossing said short edge
1702 at its middle point). Therefore, in this example the
projection of the radiation booster 1660 on the plane containing
the ground plane layer 1610 completely overlaps the ground plane
layer 1610.
[0220] FIG. 17B shows a radiating structure 1720 similar to that of
FIG. 17A, but in which the radiation booster 1660 has been arranged
with respect to the ground plane layer 1610 in such a manner that
the radiation booster is substantially close to the middle point of
the long edge 1701. Consequently, in this radiating structure 1720
approximately only 50% of the area of the projection of the
radiation booster 1660 on the plane containing the ground plane
layer 1610 overlaps the ground plane layer 1610. A radiating
structure such as the one in FIG. 17B may be advantageous when it
is required to excite a radiation mode on the ground plane layer
1610 in which the currents are substantially aligned with respect
the short edge 1702.
[0221] FIGS. 17C and 17D present two additional radiating
structures comprising the radiation booster 1630 located
substantially close to the short edge 1702. In the case of the
radiating structure 1740, the radiation booster 1630 is
advantageously located on a corner of the ground plane layer 1610,
said corner being defined by the intersection of the long edge 1701
and the short edge 1702. On the other hand, in the radiating
structure 1760 the radiation booster is located substantially close
to the middle point of the short edge 1702.
[0222] Finally, FIG. 17E shows a radiating structure 1780, which
resembles the radiating structure in FIG. 17D, but using the
radiation booster 1600 instead. In this example, it is advantageous
to protrude the radiation booster 1600 beyond the short edge 1702,
avoiding any overlapping between the projection of the radiation
booster 1600 on the plane of the ground plane layer 1610 and the
ground plane layer 1610.
[0223] Although FIGS. 17A-17E present some examples of radiating
structures using a radiation booster as those described in FIGS.
16A-16C, other possible embodiments according to the present
invention would result from replacing the particular radiation
booster shown in FIGS. 17A-17E by any of the other radiation
boosters shown in FIGS. 16A-16C.
[0224] Referring now to FIG. 18, it is shown another example of a
radiation booster. Radiation booster 1800 includes a conductive
part comprising a plurality of conductive strips. In the figure,
said conductive part comprises three conductive strips, although in
other examples said conductive part may comprise more or fewer than
three conductive strips. As depicted in FIG. 18, a first conductive
strip 1801 and a third conductive strip 1803 are arranged
substantially perpendicular to a ground plane layer 1810. A second
strip 1802 is arranged substantially parallel to the ground plane
layer 1810 and connected to the other two conductive strips, so
that a first end of the second conductive strip 1802 is connected
to a first end of the first conductive strip 1801 and a second end
of the second conductive strip 1802 is connected to a first end of
the third conductive strip 1803.
[0225] In this example, said conductive part of the radiation
booster 1800 is connected to the ground plane layer 1810. For that
purpose, a second end of the third conductive strip 1803 is
connected to the ground plane layer 1810.
[0226] The radiation booster comprises a connection point 1804
located on a second end of the first conductive strip 1801, said
connection point 1804 defining together with a connection point of
the ground plane layer 1811 an internal port of a radiating
structure 1820. Such a radiation booster 1800 may be advantageous
when it is desired to have a radiating structure that features an
input impedance at the internal port 1820 (in absence of a
radiofrequency system) having a positive imaginary part for all the
frequencies of the first frequency region (i.e., said imaginary
part being an inductive component).
[0227] FIGS. 19A-19E present some preferred placements of the
radiation booster 1800 with respect to the ground plane layer 1810.
The ground plane layer 1810 features a substantially rectangular
shape having a long edge 1901 and a short edge 1902.
[0228] In FIG. 19A it is shown a radiating structure 1900 in which
the radiation booster 1800 is arranged substantially close to the
long edge of the ground plane layer 1901. More precisely, the
radiation booster 1800 is substantially close to the middle point
of said long edge 1901. Moreover, the second conductive strip 1802
of the radiation booster 1800 is oriented substantially parallel to
the short edge of the ground plane layer 1902, so that the first
conductive strip 1801 is closer to the long edge 1901 than it is
the third conductive strip 1803. Such an arrangement has turned out
to be advantageous to enhance the coupling of energy between the
radiation booster and the ground plane layer.
[0229] FIG. 19B presents another example of a radiating structure
1920 in which the radiation booster 1800 is also arranged
substantially close to the long edge 1901 as in the previous case.
However, now the radiation booster 1800 is advantageously located
on a corner of the ground plane layer (said corner being defined by
the intersection of the long edge 1901 and the short edge 1902),
and its second conductive strip 1802 is oriented substantially
parallel to the long edge of the ground plane layer 1901. That is,
the radiation booster 1800 is arranged in such a manner that the
first conductive strip 1801 is closer to said corner of the ground
plane layer 1810 than it is the third conductive strip 1803.
[0230] FIG. 19C shows a further radiating structure 1940 including
the radiation booster 1800 still arranged in such a way that its
second conductive strip 1802 is oriented substantially parallel to
the long edge of the ground plane layer 1901, as in FIG. 19B.
However, now the radiation booster 1800 is placed substantially
close to the short edge of the ground plane layer 1902, and more
precisely approximately on the middle point of said short edge
1902. Additionally, the first conductive strip of the radiation
booster 1801 is closer to the short edge 1902 than it is the third
conductive strip 1803.
[0231] Another possible placement of the radiation booster 1800 is
as indicated in the radiating structure 1960 shown in FIG. 19D, in
which the radiation booster 1800 is substantially centered on the
ground plane layer 1810. As in previous examples, it is preferred
arranging said radiation booster 1800 so that its second conductive
strip 1802 is aligned substantially parallel to the long edge of
the ground plane layer 1901.
[0232] FIG. 19E presents a somewhat different radiating structure
comprising a radiation booster inspired in the one shown in FIG.
18. A radiating structure 1980 comprises a radiation booster 1890
including a conductive part having three conductive strips 1891,
1892, 1893. Unlike the previous examples, the radiation booster
1890 is coplanar to the ground plane layer 1810, making it possible
to embed the radiation booster 1890 and the ground plane layer 1810
in a same PCB.
[0233] Conductive strip 1891 includes a connection point that
together with a connection point of the ground plane layer 1810
defines an internal port of the radiating structure 1895.
[0234] Conductive strip 1893 is connected to the ground plane layer
1810. Conductive strip 1892 connects conductive strip 1891 with
conductive strip 1893.
[0235] As it can be observed, the radiation booster 1890 protrudes
beyond the short edge of the ground plane layer 1902, so that there
is no ground plane in the projection of said radiation booster 1890
on the plane containing the ground plane layer 1810. Moreover, the
radiation booster 1890 is advantageously located on a corner of the
ground plane layer 1810 (in particular, the corner defined by the
intersection of the long edge 1901 and the short edge 1902) and the
conductive strip 1893 is closer to said corner than it is the
conductive strip 1891.
[0236] Although FIGS. 19A-19E present some examples of radiating
structures using a radiation booster as that described in FIG. 18,
other possible embodiments according to the present invention would
result from reorienting the radiation booster 1800 to have its
second conductive strip 1802 aligned with respect to a given edge
of a ground plane layer 1810, or from replacing the radiation
booster 1800 with its coplanar equivalent (such as radiation
booster 1890).
[0237] In FIGS. 20A-20B there are shown two examples of radiation
boosters comprising a gap. The radiation booster 2000 in FIG. 20A
has already been discussed in connection with the radiation
structure of FIGS. 12A-12B. An alternative radiation booster is
depicted in FIG. 20B, in which a radiation booster 2050 comprises a
gap delimited by a plurality of segments defining a closed curve
(i.e., a curve that does not intersect the perimeter of the ground
plane layer 2010). In this example, segments 2051-2054 delimit a
gap having a polygonal shape (in fact, the shape of a square).
[0238] The radiation booster 2050 comprises a connection point 2055
located at a first point along the curve delimiting said gap. In
particular said connection point 2055 is located on a point of
segment 2053. The ground plane layer 2010 also includes a
connection point 2011, said connection point 2011 being located at
a second point along said curve, and more precisely on a point of
segment 2051. Although not always required, the connection point of
the radiation booster 2055 and the connection point of the ground
plane layer 2011 are advantageously located on segments at opposite
sides of said gap of the radiation booster 2050 (segment 2053 and
segment 2051 respectively).
[0239] Of course, FIG. 20A and FIG. 20B just present a couple of
examples of a radiation booster. Other possible examples may
include a different number of segments to delimit the gap (such as
for instance two, three, four, five, six or more) and/or said
segments could be straight, curved or a combination thereof.
[0240] FIGS. 21A-21D present some preferred placements for the
radiation boosters 2000 and 2050 with respect to the ground plane
layer 2010. The ground plane layer 2010 features a substantially
rectangular shape having a long edge 2101 and a short edge
2102.
[0241] In FIG. 21A it is shown a radiating structure 2100 similar
to the one shown in FIGS. 12A-12B but in which the radiation
booster 2050 is used instead. Said radiation booster 2050 is
arranged substantially close to the long edge of the ground plane
layer 2101. In particular, the radiation booster 2050 is
substantially close to the middle point of said long edge 2101. In
this example, the segments 2051 and 2053 (i.e., the segments
containing the connection points) are arranged so that they are
substantially parallel to the short edge of the ground plane layer
2102. Such an arrangement is advantageous to properly excite a
radiation mode on the ground plane layer 2010.
[0242] FIG. 21C presents a radiating structure 2140 also comprising
the radiation booster 2050 as in FIG. 21A, but in which said
radiation booster 2050 is arranged substantially centered with
respect to the ground plane layer 2010. That is, the radiation
booster 2050 is substantially close to the point of the ground
plane layer 2010 defined by the intersection of a first line 2103
(perpendicular to the long edge 2101 and crossing said long edge
2101 at its middle point) and a second line 2104 (perpendicular to
the short edge 2102 and crossing said short edge 2102 at its middle
point). Again, in the radiation structure 2140, the segments 2051
and 2053 (i.e., the segments containing the connection points) are
arranged so that they are substantially parallel to the short edge
of the ground plane layer 2102.
[0243] FIG. 21B presents another radiating structure 2120 including
the radiation booster 2000 placed intersecting the short edge of
the ground plane layer 2102 approximately on the middle point of
said short edge 2102. Alternatively, the radiating structure 2160
in FIG. 21D includes the radiation booster 2000 arranged
intersecting another long edge of the ground plane layer 2105. Now
the radiation booster 2000 is advantageously located substantially
close to a corner of the ground plane layer (said corner being
defined by the intersection of the long edge 2105 and the short
edge 2102).
[0244] FIG. 22, FIGS. 23A-23B, and FIG. 24 present some further
examples of radiating structures including a radiation booster
comprising a gap.
[0245] Referring now to FIG. 22, a radiating structure 2200
comprises a radiation booster 2201 and a substantially rectangular
ground plane layer 2202. In this example, the radiation booster
2201 comprises a gap having a meandering shape. Said gap is
delimited by a plurality of segments defining a curve that
comprises more than ten (10) segments and that intersects the
perimeter of the ground plane layer 2202 (i.e., the curve is
open).
[0246] FIG. 24 presents another example of a radiating structure
2400 comprising a radiation booster 2401 and a ground plane layer
2402. The radiation booster 2401 includes a gap having a U-shape.
Said gap is delimited by a plurality of segments defining a curve
that intersects the perimeter of the ground plane layer 2402 (i.e.,
the curve is open). In this example said curve comprises seven (7)
segments.
[0247] A further example is depicted in FIGS. 23A-23B, in which a
radiating structure 2300 having a radiation booster 2301 and a
substantially rectangular ground plane layer 2302. The radiation
booster 2301 comprises an inner gap 2303, an outer gap 2305 and a
conductive strip 2304 separating said inner gap 2303 from said
outer gap 2305. The conductive strip 2304 features a shape inspired
in a Hilbert curve. The inner gap 2303 is delimited by segments
2310-2312 and by a plurality of segments of the conductive strip
2304, defining a curve that intersects the perimeter of the ground
plane layer 2302.
[0248] The radiation booster 2301 comprises a connection point 2306
located at a first point along said curve, said first point being
at an end of the conductive strip 2304. The ground plane layer 2302
also comprises a connection point 2307 located at a second point
along said curve delimiting the inner gap 2303, and in particular
said second point being substantially close to an end of segment
2310.
[0249] In these examples, the radiation boosters 2201, 2301, 2401
are arranged with respect to the ground plane layer 2202, 2302,
2402 in such a manner that said radiation boosters 2201, 2301, 2401
are located substantially close to a long edge of the ground plane
layer 2202, 2302, 2402, and in particular substantially centered
with respect to said long edge. Such an arrangement is particularly
advantageous when the input impedance of a radiating structure an
has an inductive component. However, other placements for the
radiation boosters 2201, 2301, 2401 are also possible.
[0250] Moreover, a connection point of these radiation boosters
2201, 2301, 2401 is preferably located on a point of a first
segment of the curve delimiting the gap of said radiation boosters
2201, 2301, 2401, said first segment intersecting the perimeter of
the ground plane layer 2202, 2302, 2402. Likewise, a connection
point of the ground plane layer is preferably located on a point of
a second segment of said curve, said second segment being opposite
to said first segment and said second segment also intersecting the
perimeter of the ground plane layer 2202, 2302, 2402.
[0251] These radiating structures 2200, 2300, 2400 feature an input
impedance (measured at their internal port when disconnected from a
radiofrequency system) having an imaginary part with an inductive
component. Therefore, such radiating structures could be
advantageously interconnected with a radiofrequency system such as
the one shown in FIG. 13.
[0252] A further radiating structure is depicted in FIG. 25, in
which a radiating structure 2500 comprises a radiation booster 2501
and a substantially rectangular ground plane layer 2502. The
radiation booster 2501 includes a conductive part having a
substantially square conductive polygonal shape 2503 and being
coplanar to the ground plane layer 2502. The arrangement of the
radiation booster 2501 with respect to the ground plane layer is
similar to that of the example in FIGS. 4A-4B.
[0253] FIG. 26 and FIG. 27 are two examples of radiofrequency
systems comprising switching matrices.
[0254] Referring now to FIG. 26, it is shown a radiofrequency
system 2600 comprising a switching matrix 2604, a first matching
network 2605 and a second matching network 2606. The radiofrequency
system 2600 further comprises a first port 2601 for interconnection
with the internal port of a radiating structure.
[0255] The switching matrix 2604 is connected between said first
port 2601 and the first and second matching networks 2605, 2606 and
allows selecting which one of the first and second matching
networks 2605, 2606 is operationally connected to the first port
2601. The radiofrequency system 2600 also includes a control
circuit 2607 that acts on the switching matrix 2604 to select which
one of the first and second matching networks 2605, 2606 is
selected at any given time.
[0256] In this example, the radiofrequency system 2600 comprises a
second port 2602 and a third port 2603 connected to the first
matching network 2605 and to the second matching network 2606
respectively.
[0257] An alternative example is presented in FIG. 27, in which a
radiofrequency system 2700 comprises a first switching matrix 2704,
a first matching network 2705, a second matching network 2706, and
a second switching matrix 2708. The radiofrequency system also
includes a first port 2701 for connection to an internal port of a
radiating structure and a second port 2702, which may become an
external port of a radiating system for a wireless handheld or
portable device. The first switching matrix 2704 is connected
between the first port 2701 and the first and second matching
networks 2705, 2706, while the second switching matrix 2708 is
connected between the first and second matching networks 2705, 2706
and the second port 2702.
[0258] A control circuit 2707 included in the radiofrequency system
2700 acts on the first and second switching matrices 2704, 2708 to
select which one of the first and second matching networks 2705,
2706 is operationally connected to the first port 2701 and the
second port 2702.
[0259] Although the radiofrequency systems 2600, 2700 have been
described as comprising two matching networks, other possible
radiofrequency systems according to the present invention could
include three, four or more matching networks selectable by one or
more switching matrices.
* * * * *