U.S. patent application number 11/197500 was filed with the patent office on 2007-02-08 for antenna duplexer and wireless terminal using the same.
Invention is credited to Mitsutaka Hikita, Shigeki Matsuda, Naoki Matsuura, Nobuhiko Shibagaki, Kazuyuki Yokoyama.
Application Number | 20070030095 11/197500 |
Document ID | / |
Family ID | 37717129 |
Filed Date | 2007-02-08 |
United States Patent
Application |
20070030095 |
Kind Code |
A1 |
Hikita; Mitsutaka ; et
al. |
February 8, 2007 |
Antenna duplexer and wireless terminal using the same
Abstract
A technology which can realize a high-performance multiband
operation in a compact circuit configuration and is advantageous
for a wireless terminal of GSM system for which the further
increase of the demands is expected in the future is provided.
Provided is a multiband switch type antenna duplexer adopted in a
mobile phone used in TDMA system such as the GSM system, in which
the signals of respectively different first to fourth frequency
bands (GSM 850, EGSM, DCS, PCS) share a single antenna, wherein
switching elements such as receive filters and diodes are combined
in various ways to perform the high-performance band switch with
the minimum number of switching elements. The circuit of this
antenna duplexer can realize not only the size reduction of the
multiband switch antenna duplexer but also the size reduction and
performance improvement of the wireless terminal itself.
Inventors: |
Hikita; Mitsutaka;
(Hachioji, JP) ; Shibagaki; Nobuhiko; (Kokubunji,
JP) ; Matsuda; Shigeki; (Nomi, JP) ; Matsuura;
Naoki; (Yokohama, JP) ; Yokoyama; Kazuyuki;
(Yokohama, JP) |
Correspondence
Address: |
MATTINGLY, STANGER, MALUR & BRUNDIDGE, P.C.
1800 DIAGONAL ROAD
SUITE 370
ALEXANDRIA
VA
22314
US
|
Family ID: |
37717129 |
Appl. No.: |
11/197500 |
Filed: |
August 5, 2005 |
Current U.S.
Class: |
333/133 ;
333/189 |
Current CPC
Class: |
H03H 9/725 20130101;
H04B 1/52 20130101; H03H 9/706 20130101 |
Class at
Publication: |
333/133 ;
333/189 |
International
Class: |
H03H 9/00 20060101
H03H009/00 |
Claims
1. An antenna duplexer, comprising: a single antenna terminal for
transmitting and receiving signals of respectively different first,
second, third and fourth frequency bands; first means for filtering
the signals of the first, second, third and fourth frequency bands
received by said single antenna terminal into the signals of the
first and second frequency bands and the signals of the third and
fourth frequency bands; second means for filtering the signals of
the first and second frequency bands filtered by said first means
into the signals of the first frequency band and the signals of the
second frequency band; third means for filtering the signals of the
third and fourth frequency bands filtered by said first means into
the signals of the third frequency band and the signals of the
fourth frequency band; and first, second, third and fourth output
terminals each outputting the signals of the first, second, third
and fourth frequency bands filtered by said second means and said
third means.
2. A multiband switch type antenna duplexer in which signals of
respectively different first, second, third and fourth frequency
bands share a single antenna, wherein, when a transmitting
frequency band fT and a receiving frequency band fR of said first,
second, third and fourth frequency bands are respectively denoted
as fT(1) and fR(1), fT(2) and fR(2), fT(3) and fR(3) and fT(4) and
fR(4), in the case where the highest frequency of fT(1), fR(1),
fT(2) and fR(2) is lower than the lowest frequency of fT(3), fR(3),
fT(4) and fT(4), fT(1)<fR(2) and fT(3)<fR(4) are satisfied,
and fR(1) partially overlaps fT(2) and fR(3) partially overlaps
fT(4), receive filters corresponding to said first and second
frequency bands and receive filters corresponding to said third and
fourth frequency bands are provided, output terminals for reception
are independently formed on an output side of said receive filters,
and input terminals on the input side thereof are connected in
parallel to each other via a matching circuit and a phase shift
circuit, thereby forming first and third parallel connection
points, said first parallel connection point corresponding to said
first and second frequency bands is further connected in parallel
to a switching element for transmission, which is connected to a
common input point on the transmission side corresponding to said
first and second frequency bands, becomes conductive at the time of
the transmission of the signals of said first or second frequency
band, and is released at the time of the reception, via a switching
element which is connected to the ground at the time of the
transmission of the signals of said first or second frequency band
and becomes conductive at the time of the reception and a quarter
wavelength phase shift circuit, thereby forming a second parallel
connection point, said third parallel connection point
corresponding to said third and fourth frequency bands is further
connected in parallel to a switching element for transmission,
which is connected to a common terminal on the transmission side
corresponding to said third and fourth frequency bands, becomes
conductive at the time of the transmission of the signals of said
third or fourth frequency band, and is released at the time of the
reception, via a switching element which is connected to the ground
at the time of the transmission of the signals of said third or
fourth frequency band and becomes conductive at the time of the
reception and a quarter wavelength phase shift circuit, thereby
forming a fourth parallel connection point, and said second
parallel connection point and said fourth parallel connection point
are connected in parallel to each other with using an antenna
terminal as a common terminal, via a low-frequency pass filter and
a high-frequency pass filter, respectively.
3. The antenna duplexer according to claim 2, wherein control
current flowing at the time of the transmission of the signals of
said first or second frequency band and control current flowing at
the time of the transmission of the signals of said third or fourth
frequency band are almost equal to each other within the range of
.+-.20% and directly supplied from a baseband IC.
4. A multiband switch type antenna duplexer in which signals of
respectively different first and second frequency bands share a
single antenna, wherein, when a transmitting frequency band fT and
a receiving frequency band fR of said first and second frequency
bands are respectively denoted as fT(1) and fR(1) and fT(2) and
fR(2), in the case where fT(1)<fR(2) is satisfied and fR(1)
partially overlaps fT(2), receive filters corresponding to said
first and second frequency bands are provided, input terminals on
the input side of said receive filters are connected in parallel to
each other via a matching circuit and a phase shift circuit,
thereby forming a first parallel connection point, said first
parallel connection point is connected in parallel to a switching
element for transmission, which is connected to a common input
terminal on the transmission side corresponding to said first and
second frequency bands, becomes conductive at the time of the
transmission of the signals of said first or second frequency band,
and is released at the time of the reception, via a switching
element which is connected to the ground at the time of the
transmission of the signals of said first or second frequency band
and becomes conductive at the time of the reception and a quarter
wavelength phase shift circuit, thereby forming a second parallel
connection point, said second parallel connection point is directly
connected to an antenna terminal or connected to the antenna
terminal via a low-frequency pass filter or a high-frequency pass
filter, and the output terminal of the receive filter corresponding
to said first frequency band and the output terminal of the receive
filter corresponding to said second frequency band are connected in
parallel to each other, via a switching element which becomes
conductive at the time of the reception of the signals of said
first frequency band and is released at the time of the reception
of the signals of said second frequency band and via a switching
element which is connected to the ground at the time of the
reception of the signals of said first frequency band and becomes
conductive at the time of the reception of the signals of said
second frequency band and a quarter wavelength phase shift circuit,
respectively, thereby forming a third parallel connection point,
and said third parallel connection point is used as an output
terminal for reception.
5. A multiband switch type antenna duplexer in which signals of
respectively different first and second frequency bands share a
single antenna, wherein, when a transmitting frequency band fT and
a receiving frequency band fR of said first and second frequency
bands are respectively denoted as fT(1) and fR(1) and fT(2) and
fR(2), in the case where fT(1)<fR(2) is satisfied and fR(1)
partially overlaps fT(2), receive filters corresponding to said
first and second frequency bands are provided, input terminals on
the output side of said receive filters are connected in parallel
to each other via a matching circuit and a phase shift circuit,
thereby forming a third parallel connection point, and said third
parallel connection point is used as an output terminal for
reception, the input terminal of the receive filter corresponding
to said first frequency band and the input terminal of the receive
filter corresponding to said second frequency band are connected in
parallel to each other, via a switching element which becomes
conductive at the time of the reception of the signals of said
first frequency band and is released at the time of the reception
of the signals of said second frequency band and via a switching
element which is connected to the ground at the time of the
reception of the signals of said first frequency band and becomes
conductive at the time of the reception of the signals of said
second frequency band and a quarter wavelength phase shift circuit,
respectively, thereby forming a first parallel connection point,
said first parallel connection point is connected in parallel to a
switching element for transmission, which is connected to a common
input terminal on the transmission side corresponding to said first
and second frequency bands, becomes conductive at the time of the
transmission of the signals of said first or second frequency band,
and is released at the time of the reception, via a switching
element which is connected to the ground at the time of the
transmission of the signals of said first or second frequency band
and becomes conductive at the time of the reception and a quarter
wavelength phase shift circuit, thereby forming a second parallel
connection point, and said second parallel connection point is
directly connected to an antenna terminal or connected to the
antenna terminal via a low-frequency pass filter or a
high-frequency pass filter.
6. A multiband switch type antenna duplexer in which signals of
respectively different first and second frequency bands share a
single antenna, wherein a receive filter corresponding to said
first frequency band and a switching element for reception
corresponding to said second frequency band, which becomes
conductive at the time of the reception of the signals of said
second frequency band and is released in other cases, are provided,
output terminals for reception are independently formed on the
output side of said receive filter and said switching element for
reception, and said receive filter is connected in parallel to said
switching element for reception on the input side via a matching
circuit and a phase shift circuit but said switching element for
reception is directly connected to said receive filter, thereby
forming a first parallel connection point, said first parallel
connection point is further connected in parallel to a switching
element for transmission, which is connected to a common input
terminal on the transmission side corresponding to said first and
second frequency bands, becomes conductive at the time of the
transmission of the signals of said first or second frequency band,
and is released at the time of the reception, via a switching
element which is connected to the ground at the time of the
transmission of the signals of said first or second frequency band
and becomes conductive at the time of the reception and a quarter
wavelength phase shift circuit, thereby forming a second parallel
connection point, and said second parallel connection point is
directly connected to an antenna terminal or connected to the
antenna terminal via a low-frequency pass filter or a
high-frequency pass filter.
7. The antenna duplexer according to claim 6, wherein a receive
filter is externally attached to the output terminal for reception
corresponding to said second frequency band according to need.
8. A multiband switch type antenna duplexer in which signals of
respectively different first and second frequency bands share a
single antenna, wherein receive filters corresponding to said first
frequency band and said second frequency band are provided, output
terminals for reception are independently formed on the output side
of said receive filters, and input terminals on the input side
thereof are connected in parallel to each other via a matching
circuit and a phase shift circuit, thereby forming a first parallel
connection point, said first parallel connection point is connected
in parallel to a switching element for transmission, which is
connected to a common input terminal on the reception side
corresponding to said first and second frequency bands, becomes
conductive at the time of the transmission of the signals of said
first or second frequency band, and is released at the time of the
reception, via a switching element which is connected to the ground
via a resistor at the time of the transmission of the signals of
said first or second frequency band and becomes conductive at the
time of the reception and a quarter wavelength phase shift circuit
and further via a switching element which is connected to the
ground at the time of the transmission of the signals of said first
or second frequency band and becomes conductive at the time of the
reception and a quarter wavelength phase shift circuit, thereby
forming a second parallel connection point, and said second
parallel connection point is directly connected to an antenna
terminal or connected to the antenna terminal via a low-frequency
pass filter or a high-frequency pass filter.
9. The antenna duplexer according to claim 2, wherein a balun
circuit for converting a single-ended output to a balanced output
is connected to a front stage of at least one of the output
terminals for reception, and a receiving signal is outputted via a
differential output terminal.
10. The antenna duplexer according to claim 9, wherein said balun
circuit is comprised of a circuit composed of a serial arm
inductance and a parallel arm capacitance from an input side
between said input side and one of said differential output
terminals and a circuit composed of a serial arm capacitance and a
parallel arm inductance from said input side between said input
side and the other of said differential output terminals, or said
balun circuit is comprised of a circuit composed of a serial arm
inductance, a parallel arm capacitance, a serial arm inductance,
and a parallel arm capacitance from said input side between said
input side and one of said differential output terminals and a
circuit composed of a serial arm capacitance, a parallel arm
inductance, a serial arm capacitance, and a parallel arm inductance
from said input side between said input side and the other of said
differential output terminals.
11. The antenna duplexer according to claim 2, wherein said receive
filter is comprised of a SAW filter or a FBAR filter, and said
switching element is comprised of a pin diode switch, a GaAs switch
or a MEMS switch.
12. A wireless terminal using the antenna duplexer according to
claim 1, wherein said wireless terminal is a GSM mobile phone based
on a TDMA system, and a direct conversion system or a low IF system
is used as a demodulation system.
Description
TECHNICAL FIELD OF THE INVENTION
[0001] The present invention relates to an antenna duplexer (a
radio frequency (abbreviated as RF, hereinafter) circuit for
antenna duplexer) which makes it possible to achieve the multiband
wireless terminal suitable for a mobile phone or the like in the
TDMA (Time Division Multiple Access) system such as the GSM (Global
System for Mobile Communications) mobile phone. More particularly,
it relates to a technology effectively applied to the case where
the antenna duplexer (RF circuit for antenna duplexer) is adopted
to realize a compact and high-performance terminal.
BACKGROUND OF THE INVENTION
[0002] Conventionally, when realizing the multiband operation in a
wireless terminal in the TDMA system, an antenna switch module in
which a plurality of switches for selecting the transmitting and
receiving frequency signals corresponding to each band are provided
right behind the antenna has been used. For example, as shown in
FIG. 1, the demand from the dual-band terminal of the 900 MHz EGSM
(Extended GSM) and the 1.8 GHz DCS (Digital Communication Systems)
to the triple-band terminal obtained by adding the 1.9 GHz PCS
(Personal Communication Service) and to the quad-band terminal
obtained by further adding the 850 MHz GSM has been increasing.
SUMMARY OF THE INVENTION
[0003] Incidentally, in the above-described wireless terminal in
the TDMA system, with the increase of the demand for the multiband
terminal, for example, from the dual-band terminal of the 900 MHz
EGSM and the 1.8 GHz DCS to the triple-band terminal obtained by
adding the 1.9 GHz PCS and to the quad-band terminal obtained by
further adding the 850 MHz GSM, the operation thereof has become
more and more difficult. More specifically, along with the increase
of the demand for the multiband terminal, the number of switches to
be used exponentially increases.
[0004] In such a circumstance, the present invention is intended to
solve the problem of the exponential increase of the number of
switches to be used, and an object of the present invention is to
provide the technology which is capable of achieving the
high-performance multiband operation with the compact circuit
configuration and is quite effective for the wireless terminal of
the GSM system, for which the further increase of the demands is
expected in the future.
[0005] The above and other objects and novel characteristics of the
present invention will be apparent from the description of this
specification and the accompanying drawings.
[0006] The typical ones of the inventions disclosed in this
application will be briefly described as follows.
[0007] In the present invention, the band selection function to
switch the bands for the multiband operation is equivalently
provided not only to the switches but also to the filters on the
latter stage used in the receiver system. By doing so, the number
of switches can be greatly reduced even for the quad-band terminal
having the largest number of bands at present. In particular, a
surface acoustic wave (abbreviated as SAW hereinafter) filter or a
film bulk acoustic resonator (abbreviated as FBAR hereinafter)
filter is used for the filter unit, and a pin diode, or a GaAs
switch or a MEMS (Micro-Electronic-Mechanical System) switch is
used for the switch unit. Therefore, the further effect for the
size reduction can be obtained. In addition, a new synthesis method
of output signals from two receive filters is proposed to solve the
problem of the increase in the number of pins resulting from the
recent combination with an IC for a direct conversion (abbreviated
as DC hereinafter) demodulation system or an IC for
low-intermediate frequency (abbreviated as IF hereinafter)
demodulation system.
[0008] Also, a new antenna duplexer (RF circuit for antenna
duplexer) is proposed to achieve the multiband operation by the
arbitrary combination in wireless terminals which are assumed to be
mass-produced. Furthermore, a new circuit configuration is provided
to facilitate the calibration of the direct current offset caused
when combined with the IC for DC demodulation system or the IC for
low-IF demodulation system.
[0009] That is, the antenna duplexer according to the present
invention comprises: a single antenna terminal for transmitting and
receiving signals of respectively different first to fourth
frequency bands; first means for filtering the signals of the first
to fourth frequency bands received by the single antenna terminal
into the signals of the first and second frequency bands and the
signals of the third and fourth frequency bands; second means for
filtering the signals of the first and second frequency bands
filtered by the first means into the signals of the first frequency
band and the signals of the second frequency band; third means for
filtering the signals of the third and fourth frequency bands
filtered by the first means into the signals of the third frequency
band and the signals of the fourth frequency band; and first to
fourth output terminals each outputting the signals of the first to
fourth frequency bands filtered by the second means and the third
means.
[0010] More specifically, an antenna duplexer according to the
present invention is applied to a multiband switch type antenna
duplexer in which signals of respectively different first to fourth
frequency bands share a single antenna, and when a transmitting
frequency band fT and a receiving frequency band fR of the first to
fourth frequency bands are respectively denoted as fT(1) to fT(4)
and fR(1) to fR(4), in the case where the highest frequency of
fT(1), fR(1), fT(2) and fR(2) is lower than the lowest frequency of
fT(3), fR(3), fT(4) and fT(4), fT(1)<fR(2) and fT(3)<fR(4)
are satisfied, and fR(1) partially overlaps fT(2) and fR(3)
partially overlaps fT(4), the antenna duplexer forms the connection
configuration as follows.
[0011] For example, receive filters corresponding to each of the
first to fourth frequency bands are provided, output terminals for
reception are independently formed on an output side of the receive
filters, and input terminals thereof are connected in parallel to
each other via a matching circuit and a phase shift circuit,
thereby forming first and third parallel connection points,
[0012] the first parallel connection point corresponding to the
first and second frequency bands is further connected in parallel
to a switching element for transmission, which is connected to a
common input point on the transmission side corresponding to the
first and second frequency bands, via a switching element and a
quarter wavelength phase shift circuit, thereby forming a second
parallel connection point,
[0013] the third parallel connection point corresponding to the
third and fourth frequency bands is further connected in parallel
to a switching element for transmission, which is connected to a
common terminal on the transmission side corresponding to the third
and fourth frequency bands, via a switching element and a quarter
wavelength phase shift circuit, thereby forming a fourth parallel
connection point, and
[0014] the second parallel connection point and the fourth parallel
connection point are connected in parallel to each other with using
an antenna terminal as a common terminal, via a low-frequency pass
filter and a high-frequency pass filter, respectively.
[0015] Also, another antenna duplexer according to the present
invention is applied to a multiband switch type antenna duplexer in
which signals of respectively different first to fourth frequency
bands share a single antenna, and when a transmitting frequency
band fT and a receiving frequency band fR of the first and second
frequency bands are respectively denoted as fT(1) and fT(2) and
fR(1) and fR(2), in the case where fT(1)<fR(2) is satisfied and
fR(1) partially overlaps fT(2), the antenna duplexer forms the
connection configuration as follows.
[0016] For example, receive filters corresponding to the first and
second frequency bands are provided, input terminals on the input
side of said receive filters are connected in parallel to each
other via a matching circuit and a phase shift circuit, thereby
forming a first parallel connection point,
[0017] the first parallel connection point is connected in parallel
to a switching element for transmission, which is connected to a
common input terminal on the transmission side corresponding to the
first and second frequency bands, via a switching element and a
quarter wavelength phase shift circuit, thereby forming a second
parallel connection point,
[0018] the second parallel connection point is directly connected
to an antenna terminal or connected to the antenna terminal via a
low-frequency pass filter or a high-frequency pass filter, and
[0019] the output terminals of the receive filters corresponding to
the first and second frequency bands are connected in parallel to
each other via a switching element and via a switching element and
a quarter wavelength phase shift circuit, respectively, thereby
forming a third parallel connection point, and the third parallel
connection point is used as an output terminal for reception.
[0020] Alternatively, the connection configuration obtained by
changing the input side and the output side of the receive filters
in the above-described configuration and that obtained by changing
the circuits and elements interposed between the first parallel
connection point and the second parallel connection point and
between the first parallel connection point and the third
connection point in the above-described configuration are also
available.
BRIEF DESCRIPTIONS OF THE DRAWINGS
[0021] FIG. 1 is a diagram showing an example of the frequency
allocation of the GSM mobile phone system;
[0022] FIG. 2 is a block diagram showing a quad-band switch type
antenna duplexer according to the first embodiment of the present
invention;
[0023] FIG. 3 is a block diagram showing a multiband switch type
antenna duplexer according to the second embodiment of the present
invention;
[0024] FIG. 4 is a block diagram showing another multiband switch
type antenna duplexer according to the second embodiment of the
present invention;
[0025] FIG. 5 is a block diagram showing a multiband switch type
antenna duplexer according to the third embodiment of the present
invention;
[0026] FIG. 6 is a block diagram showing a multiband switch type
antenna duplexer (specific balun circuit) according to the third
embodiment of the present invention;
[0027] FIG. 7 is a block diagram showing a multiband switch type
antenna duplexer (another specific balun circuit) according to the
third embodiment of the present invention;
[0028] FIG. 8 is a block diagram showing a multiband switch type
antenna duplexer according to the fourth embodiment of the present
invention;
[0029] FIG. 9 is a block diagram showing a multiband switch type
antenna duplexer according to the fifth embodiment of the present
invention;
[0030] FIG. 10 is a block diagram showing a wireless terminal of
the DC demodulation system or the low IF demodulation system using
the antenna duplexer according to the present invention;
[0031] FIG. 11 is a diagram showing the SAW resonator according to
an embodiment of the present invention;
[0032] FIG. 12 is a diagram showing the FBAR resonator according to
an embodiment of the present invention;
[0033] FIG. 13 is a diagram showing the impedance characteristics
of the SAW resonator and the FBAR resonator according to an
embodiment of the present invention;
[0034] FIG. 14 is a diagram showing a ladder type filter according
to an embodiment of the present invention;
[0035] FIG. 15 is a diagram showing the SAW filter according to an
embodiment of the present invention;
[0036] FIG. 16 is a diagram showing the FBAR filter according to an
embodiment of the present invention;
[0037] FIG. 17 is a cross-sectional view showing the FBAR filter
according to an embodiment of the present invention; and
[0038] FIG. 18 is a block diagram showing a multiband switch type
antenna duplexer according to an embodiment of the present
invention.
DESCRIPTIONS OF THE PREFERRED EMBODIMENTS
[0039] Hereinafter, embodiments of the present invention will be
described in detail with reference to the accompanying drawings.
Note that components having the same function are denoted by the
same reference symbols throughout the drawings for describing the
embodiment, and the repetitive description thereof will be
omitted.
[0040] FIG. 1 is a diagram showing an example of a frequency
allocation of the GSM mobile phone system. The frequency allocation
of the GSM mobile phone system adopted in more than half of the
world mainly in Europe, that is, the frequency allocation adopted
in Europe is the 900 MHz EGSM and the 1.8 GHz DCS, and that adopted
in the United States is the 850 MHz GSM and the 1.9 GHz PCS.
[0041] As shown in FIG. 1, in the United states and Europe, the
transmitting frequency band (fT) is located on a lower side of the
receiving frequency band (fR) because of the easiness of the
circuit configuration of the wireless terminal. In the recent
wireless terminal, the dual-band terminal which can handle both
frequencies of EGSM and DCS with a single terminal has become more
and more popular. Also, for a business person or the like who goes
back and forth between Europe and the United States, it is
preferable that the same terminal can be used in both Europe and
the United States. Consequently, the demands for the triple-band
terminal obtained by adding PCS to the dual-band terminal and the
quad-band terminal obtained by adding both PCS and GSM 850 has been
increasing.
First Embodiment
[0042] FIG. 2 shows an example of the first embodiment of the
present invention. An example of the RF circuit for antenna
duplexer assumed to be used for the quad-band terminal is shown in
FIG. 2. By the adoption of this RF circuit, it becomes possible to
pair the transmitting and receiving frequencies of each system and
to handle the bands corresponding to four systems of the respective
frequencies of EGSM, DCS, PCS and GSM 850 with a single
antenna.
[0043] First, the configuration of the wireless terminal will be
described in brief with using the quad-band terminal as an example.
FIG. 10 is a simplified block diagram showing the wireless
terminal. Since it handles the RF signals of both 824 to 960 MHz
band and 1.71 to 1.99 GHz band, the circuit is generally large and
complicated. Various types of new circuit systems have been
proposed for the size reduction of the terminal. In the OPLL
(Offset Phase Lock Loop) modulation method adopted in the
transmitter system, the modulation is directly applied to the VCO
(Voltage Controlled Oscillator) by the output of the PLL circuit.
As a result, the circuit configuration of the transmitter system
can be significantly simplified. Meanwhile, with respect to the
receiver system, the study for the DC demodulation system in which
the relatively high IF as the conventional system is not used and
frequencies of the receiving signal and the local signal are made
equal and that for the low IF demodulation system in which they
differ only slightly have been started. FIG. 10 is a block diagram
showing the case where the OPLL modulation system is used for the
modulation system and the DC demodulation system is used for the
receiver system.
[0044] In general, the size of RF-IC which adopts the
above-described modulation system and demodulation system is quite
large. Also, since the RF signals of both 824 to 960 MHz band and
1.71 to 1.99 GHz band are handled in the chip, it is much
influenced by the crosstalk between signal lines and the
common-mode noise from the earth. In the receiver system, in
particular, it is known that the influence by the common-mode noise
can be reduced by using a differential type signal line in the RF
circuit. Therefore, in the receiver system in the block diagram
shown in FIG. 10, the RF circuits in the RF-IC are all composed of
the differential type circuits.
[0045] The antenna duplexer according to the present invention
enclosed by dotted lines in FIG. 10 separates the transmitting and
receiving signals, transmits the transmitting signals from the
transmitter to the antenna and the minute receiving signal from the
antenna to the receiver as a differential signal of the RF. By
doing so, the transmission and reception by the single antenna can
be realized. Also, the antenna duplexer for the quad-band terminal
separates the RF signal of 824 to 960 MHz band and the RF signal of
1.71 to 1.99 GHz band. More concretely, since the frequency of the
EGSM and that of the GSM 850 are close to each other in the
transmission RF signal, both the transmission signals are commonly
amplified to about 2 W by the high power amplifier (abbreviated as
HPA hereinafter) of the 824 to 915 MHz band. In addition, since the
frequencies of the transmission signals of the DCS and PCS are
close to each other, both the transmission signals are amplified to
about 1 W by another HPA of the 1710 to 1910 MHz band. Then, they
are supplied to the corresponding transmitting terminals of the
antenna duplexer.
[0046] First, the RF signal of 869 to 960 MHz band and the RF
signal of 1.805 to 1.99 GHz band are separated from the receiving
RF signal by the antenna duplexer, and then, they are separated
into the RF signals of EGSM and GSM 850 and those of DCS and PCS by
each two filter, that is, total of four filters. These RF signals
are converted into differential signals by a balun circuit and
supplied to the low noise amplifier (abbreviated as LNA
hereinafter) by the receiving terminal. The RF signals passing
through the LNA are converted into the signals of baseband by a
mixer (abbreviated as MIX hereinafter) and then demodulated as
sound or data after passing through a signal processing circuit, a
baseband logic, and the like.
[0047] Based on the description of the entire configuration diagram
of the terminal shown above, the RF circuit for antenna duplexer
for the quad-band terminal shown in FIG. 2 according to the first
embodiment of the present invention will be described. As shown in
the frequency allocation in FIG. 1 including the examples of Europe
and the United State, in the course of progress of the mobile
communication, the service of the initial system was started at the
frequency of 1 GHz or lower in each country and thereafter the new
system at the frequency of 1 to 2 GHz was added. Therefore, when
the transmitting and receiving frequencies of the European system
(EGSM, DCS) and the US system (GSM 850, PCS) are arranged in
increasing order, and the transmitting and receiving frequencies of
the GSM 850, that is, those of the first system are denoted as
fT(1) and fR(1), the transmitting and receiving frequencies of the
EGSM, that is, those of the second system are denoted as fT(2) and
fR(2), the transmitting and receiving frequencies of the DCS, that
is, those of the third system are denoted as fT(3) and fR(3) and
the transmitting and receiving frequencies of the PCS, that is,
those of the fourth system are denoted as fT(4) and fR(4), this RF
circuit for antenna duplexer is particularly important in the
system configuration in which the highest frequency of fT(1),
fR(1), fT(2) and fR(2) is lower than the lowest frequency of fT(3),
fR(3), fT(4) and fT(4) and in the system in which fT(1)<fR(2)
and fT(3)<fR(4) are satisfied and fR(1) partially overlaps fT(2)
and fR(3) partially overlaps fT(4) as shown in FIG. 1.
[0048] As shown in FIG. 2, a low-frequency pass filter 21 and a
high-frequency pass filter 41 are connected to an antenna terminal
Ant in parallel to each other, and the signals corresponding to the
first and second systems are transmitted and received via the
low-frequency pass filter 21 through the path shown in the upper
part of FIG. 2 and the signals corresponding to the third and
fourth systems are transmitted and received via the high-frequency
pass filter 41 through the path shown in the lower part of FIG. 2.
The receive filters 27 and 24 corresponding to the first and second
systems and the receiver filters 44 and 47 corresponding to the
third and fourth systems are provided, and the output terminals for
reception Rx(GSM 850), Rx(EGSM), Rx(DCS) and Rx(PCS) are
independently formed on the output side of the above-described
filters as shown in FIG. 2. On the input side, the input terminals
thereof are connected in parallel to each other via matching
circuit/phase-shift circuits 26, 23, 43 and 46 under the condition
that, at the frequency in the pass band of each filter, the
impedance in the other filter becomes high impedance (that is, the
condition that the impedance in the filter (EGSM) 24 becomes high
impedance at fR(1) and the impedance in the filter (GSM 850) 27
becomes high impedance at fR(2), similarly, the impedance in the
filter (PCS) 47 becomes high impedance at fR(3) and the impedance
in the filter (DCS) 44 becomes high impedance at fR(4)), and a
first parallel connection point 1 and a third parallel connection
point 3 are formed.
[0049] The first parallel connection point 1 corresponding to the
first and second systems is connected to a second parallel
connection point 2 via a diode (switching element) 9, which is
connected to the ground at the time of the transmission in the
first or second system and becomes conductive at the time of the
reception, and an equivalent quarter wavelength phase shift circuit
22. Other circuit connected to the second parallel connection point
2 is composed of a diode (switching element for transmission) 10,
which is connected to a common input terminal Tx (EGSM/GSM 850) on
the transmission side corresponding to the first and second
systems, becomes conductive at the time of the transmission in the
first or second system, and is released at the time of the
reception.
[0050] The third parallel connection point 3 corresponding to the
third and fourth systems is connected to a fourth parallel
connection point 4 via a diode (switching element) 11, which is
connected to the ground at the time of the transmission in the
third or fourth system and becomes conductive at the time of the
reception, and an equivalent quarter wavelength phase shift circuit
42. Other circuit connected to the fourth parallel connection point
4 is composed of a diode (switching element for transmission) 12,
which is connected to a common terminal Tx (DCS/PCS) on the
transmission side corresponding to the third and fourth systems,
becomes conductive at the time of the transmission in the third or
fourth system, and is released at the time of the reception. In
addition, the second parallel connection point 2 and the fourth
parallel connection point 4 are connected in parallel to each other
with using the antenna terminal Ant as a common terminal via the
low-frequency pass filter 21 and the high-frequency pass filter 41,
respectively.
[0051] Next, the transmitting and receiving operations of each
system will be concretely described. For example, in the
transmitting operation of the first or second system, positive
control voltage is applied to a control terminal Vcont-Tx (EGSM/GSM
850). The control voltage turns on the diode 10 on the transmission
path and puts the diode 9 on the reception path to the ground. More
specifically, as shown in FIG. 10, the transmitting power from the
HPA for the first or second system is inputted to the transmitting
terminal Tx (EGSM/GSM 850) and supplied to the antenna terminal
through the diode 10 on the transmission path, the second parallel
connection point 2 and the low-frequency pass filter 21. At this
time, if seen via the equivalent quarter wavelength phase shift
circuit 22, the impedance in the reception side from the second
parallel connection point 2 is the very high impedance, that is,
released because the diode 9 on the reception path is connected to
the ground. Therefore, it scarcely influences the passage of the
transmitting power. Consequently, the transmitting power inputted
to the transmitting terminal is hardly attenuated and supplied to
the antenna terminal.
[0052] At the time of the reception in the first or second system,
the control terminal voltage to the Vcont-Tx (EGSM/GSM 850) is set
to 0 V. More specifically, the diodes of the transmission path and
the reception path are both in an off state. Therefore, the
receiving signal from the antenna terminal reaches the first
parallel connection point 1 through the low-frequency pass filter
21 and the second parallel connection point 2. In this case, the
receiving signal at fR(1) is outputted to the output terminal for
reception Rx (GSM 850) through the filter (GSM 850) 27 because the
filter (EGSM) 24 becomes high impedance at fR(1) as described
above. Similarly, the receiving signal at fR(2) is outputted to the
output terminal for reception Rx (EGSM) through the filter (EGSM)
24 because the filter (GSM 850) 27 becomes high impedance at fR(2)
as described above.
[0053] Next, the transmitting and receiving operations of the third
and fourth systems will be described. For example, in the
transmitting operation of the third or fourth system, positive
control voltage is applied to a control terminal Vcont-Tx
(DCS/PCS). The control voltage turns on the diode 12 on the
transmission path and puts the diode 11 on the reception path to
the ground. More specifically, as shown in FIG. 10, the
transmitting power from the HPA for the third or fourth system is
inputted to the transmitting terminal Tx (DCS/PCS) and supplied to
the antenna terminal through the diode 12 on the transmission path,
the fourth parallel connection point 4 and the high-frequency pass
filter 41. At this time, if seen via the equivalent quarter
wavelength phase shift circuit 42, the impedance in the reception
side from the fourth parallel connection point 4 is the very high
impedance, that is, released because the diode 11 on the reception
path is connected to the ground. Therefore, it scarcely influences
the passage of the transmitting power. Consequently, the
transmitting power inputted to the transmitting terminal is hardly
attenuated and supplied to the antenna terminal.
[0054] At the time of the reception in the third or fourth system,
the control terminal voltage to the Vcont-Tx (DCS/PCS) is set to 0
V. More specifically, the diodes of the transmission path and the
reception path are both in an off state. Therefore, the receiving
signal from the antenna terminal reaches the third parallel
connection point 3 through the high-frequency pass filter 41 and
the fourth parallel connection point 4. In this case, the receiving
signal at fR(3) is outputted to the output terminal for reception
Rx (DCS) through the filter (DCS) 44 because the filter (PCS) 47
becomes high impedance at fR(3) as described above. Similarly, the
receiving signal at fR(4) is outputted to the output terminal for
reception Rx (PCS) through the filter (PCS) 47 because the filter
(DCS) 44 becomes high impedance at fR(4) as described above. Also,
in this circuit configuration, the control currents in the
transmission, that is, the control current in the transmission in
the first or second system is almost equal to the control current
in the transmission in the third or fourth system (within the range
of .+-.20%), and the baseband IC controlling the current and the
interface between the IC and the circuit configuration can be
realized in the same circuit. Therefore, it is possible to simplify
the design.
[0055] As described above, the switch-type antenna duplexer having
the above configuration can process the quad-band transmitting and
receiving signals corresponding to the first to fourth systems
shown in FIG. 1. Each of the transmitting signals from the
transmitting terminal is supplied to the antenna terminal and each
of the receiving signals from the antenna terminal is filtered and
then outputted to the output terminals for reception. Also, it is
possible to achieve the good characteristic that the control
current is required only in the transmitting operation and is not
required in the reception waiting time in which demand for the
power consumption is severe.
[0056] Also, this configuration is particularly effective for the
system in which fR(1) partially overlaps fT(2) or fR(3) partially
overlaps fT(4). In the transmission in the second or fourth system,
the transmitting power thereof passes through the pass band of the
receive filter of the first system or the third system. Therefore,
the attenuation by the filter cannot be expected and there is the
possibility that the low-noise amplifier for reception is broken.
In this configuration, since minimum number of switching elements
(for example, diode) and minimum number of control terminals are
used and the reception path is connected to the ground in the
transmission time, it is possible to ensure the attenuation
regardless of the receive filter. As a result, this configuration
is particularly effective for the system in which fR(1) partially
overlaps fT(2), or fR(3) partially overlaps fT(4).
Second Embodiment
[0057] Subsequently, FIG. 3 and FIG. 4 shown an example of the 15
second embodiment of the present invention. This configuration is
common to the RF circuit for multiband switch-type antenna duplexer
such as dual band, triple band and quad band and more. In general,
the number of RF-IC pins is increased with the development of the
multiband operation, and it is expected that the problem of the
number of pins will become severer in the future. An object of the
configuration of this proposal is to solve the problem.
[0058] The RF circuit with the configuration of this embodiment is
effective for the system in which fT(1)<fR(2) is satisfied and
fR(1) partially overlaps fT(2) when the transmitting and receiving
frequency bands of the first system are denoted as fT(1) and fR(1)
and the transmitting and receiving frequency bands of the second
system are denoted as fT(2) and fR(2).
[0059] In FIG. 3, the first system is, for example, the GSM 850 and
the second system is, for example, the EGSM. The circuit enclosed
by the dotted lines is the newly proposed RF circuit, and the part
in the parentheses is the circuit components to be added when the
quad-band or triple-band antenna duplexer is formed. The receive
filters (GSM 850) 27 and (EGSM) 24 corresponding to the first and
second systems are provided. On the input side of the filters, the
input terminals thereof are connected in parallel to each other via
matching circuit/phase-shift circuits 26 and 23 under the condition
that, at the frequency in the pass band of each filter, the
impedance in the other filter becomes high impedance (that is, the
condition that the impedance in the filter (EGSM) 24 becomes high
impedance at fR(1) and the impedance in the filter (GSM 850) 27
becomes high impedance at fR(2)), and the first parallel connection
point 1 is formed.
[0060] The first parallel connection point 1 is connected to the
second parallel connection point 2 via a diode (switching element)
9, which is connected to the ground at the time of the transmission
in the first or second system, and the equivalent quarter
wavelength phase shift circuit 22. Other circuit connected to the
second parallel connection point 2 is composed of a diode
(switching element for transmission) 10, which is connected to a
common input terminal on the transmission side corresponding to the
first and second systems and is released at the time of the
reception in the first or second system. The second parallel
connection point 2 is connected to the antenna terminal via the
low-frequency pass filter 21 or the high-frequency pass filter 41
(an example of using the low-frequency pass filter 21 is shown in
FIG. 3) or directly connected to the antenna terminal without the
filter (because filter is not always necessary particularly in the
dual-band operation).
[0061] The output terminal of the receive filter corresponding to
the first system and the output terminal of the receive filter
corresponding to the second system are connected in parallel to
each other via a diode (switching element) 14, which becomes
conductive at the time of the reception in the first system and is
released at the time of the reception in the second system, and via
a diode (switching element) 13, which is connected to the ground at
the time of the reception in the first system and becomes
conductive at the time of the reception in the second system,
respectively, and an equivalent quarter wavelength phase shift
circuit 29, and a third parallel connection point 5 is formed. This
third parallel connection point 5 is the output terminal for
reception Rx (EGSM/GSM 850) and used as the common terminal of the
first and second systems. By doing so, the number of receiving
terminals can be reduced, and it is possible to solve the problem
of the increase in the number of pins.
[0062] The operation in the transmission and reception in each
system will be concretely described. In FIG. 3, when the circuit
components in the left parentheses are added, the circuit
configuration for the quad band is obtained, and when the circuit
components in the right parentheses are added, the circuit
configuration for the triple band is obtained. Also, when the
circuit components in the parentheses are not added and the
low-frequency pass filter 21 is removed, the circuit configuration
for the dual band is obtained. The basic operation is identical to
that of the upper half of FIG. 2, that is, that of the first and
second systems. However, at the time of the reception in the first
system, the positive control voltage is further applied to the
control terminal Vcont-Rx (GSM 850). The control voltage turns on
the diode on the reception path of the first system and puts the
diode on the reception path of the second system to the ground.
More specifically, the receiving signal at fR(1) is outputted to
the common output terminal for reception Rx (EGSM/GSM 850) through
the filter (GSM 850) 27. At this time, the impedance from the third
parallel connection point 5 to the filter (EGSM) 24 via the
equivalent quarter wavelength phase shift circuit 29 becomes the
high impedance because the diode on the reception path of the
second system is connected to the ground. Therefore, the filter
(EGSM) 24 does not influence the receiving signal of fR(1).
[0063] Next, at the time of the reception in the second system, the
control terminal voltage to the Vcont-Tx (GSM 850) is set to 0 V.
More specifically, the diodes of the first and second transmission
paths are both in an off state. Therefore, the receiving signal of
fR(2) is outputted to the output terminal for reception Rx
(EGSM/GSM 850) through the filter (EGSM) 24. At this time, since
the diode 14 of the reception path of the first system is in an off
state, the impedance from the third parallel connection point 5 to
the filter (EGSM) 24 becomes the high impedance. Therefore, the
receiving signal of fR(2) is not influenced. As described above,
the shared use of the receiving terminals of the first and second
systems can be realized.
[0064] In general, passive elements such as filters have the
reciprocity, and the characteristics thereof are not changed even
when the input and the output are inverted. FIG. 4 shows another
example of the configuration obtained by modifying the
configuration of FIG. 3. In the configuration of FIG. 4, the
input/output relation in the circuit between the first parallel
connection point 1 and the third parallel connection point 5 of
FIG. 3 is inverted. The resultant circuit is shown in FIG. 4. In
FIG. 4, it can be easily understood that the electrical properties
are equal to those of the circuit in FIG. 3 due to the reciprocity
of the passive elements. It is evident that the present invention
includes the configuration of FIG. 4.
[0065] More specifically, in FIG. 4, the input terminals on the
output side of the receive filters (GSM 850) 27 and (EGSM) 24
corresponding to the first and second systems are connected in
parallel to each other via the matching circuit/phase-shift
circuits 26 and 23, and the third parallel connection point 5 is
formed. The input terminal of the receive filter corresponding to
the first system and the input terminal of the receive filter
corresponding to the second system are connected in parallel to
each other via a diode (switching element) 14, which becomes
conductive at the time of the reception in the first system and is
released at the time of the reception in the second system, and via
a diode (switching element) 13, which is connected to the ground at
the time of the reception in the first system and becomes
conductive at the time of the reception in the second system, and
an equivalent quarter wavelength phase shift circuit 29,
respectively, and the first parallel connection point 1 is
formed.
Third Embodiment
[0066] Subsequently, FIG. 5 to FIG. 7 show an example of the third
embodiment of the present invention. In the circuit in FIG. 5, a
balun circuit 30 is introduced between the third parallel
connection point 5 and the common terminal for reception in the
circuit of FIG. 3 or FIG. 4 (example of using the circuit of FIG. 3
is shown in FIG. 5), so that the common output terminal for
reception is changed to the differential output terminal. By doing
so, since not only the number of receiving terminals but also the
number of balun circuits can be reduced, the simplification of the
entire circuit and the cost reduction can be achieved. FIG. 6 shows
a concrete example of an embodiment including the balun circuit of
FIG. 5. More specifically, the balun circuit is formed of the
circuit composed of the serial arm inductance and the parallel arm
capacitance from the side of the parallel connection point 5
between the third parallel connection point 5 and one of the
differential output terminals (-) and the circuit composed of the
serial arm capacitance and the parallel arm inductance from the
side of the parallel connection point 5 between the third parallel
connection point 5 and the other of the differential output
terminals (+). As a result, the amplitude balance variation of the
differential output of .+-. 1.5 dB or less and the phase balance
variation thereof of .+-. 15.degree. or less can be realized so as
to correspond to both of the first and second systems.
[0067] FIG. 7 shows another example of an embodiment including the
balun circuit of FIG. 5. More specifically, the balun circuit is
formed of the circuit composed of the serial arm inductance,
parallel arm capacitance, serial arm inductance and the parallel
arm capacitance from the side of the parallel connection point 5
between the third parallel connection point 5 and one of the
differential output terminals (-) and the circuit composed of the
serial arm capacitance, parallel arm inductance, serial arm
capacitance and the parallel arm inductance from the side of the
parallel connection point 5 between the third parallel connection
point 5 and the other of the differential output terminals (+). As
a result, the amplitude balance variation of the differential
output of .+-.1.0 dB or less and the phase balance variation
thereof of .+-.10.degree. or less can be realized for both of the
first and second systems.
[0068] Although the demand for the balance of the receiving output
signal differs depending on the system design of the receiver unit
of the wireless terminal, the amplitude variation of .+-.1.0 to
.+-.1.5 dB or less and the phase variation of .+-.10 to
.+-.15.degree. or less are demanded in general. The circuit
configuration described above can satisfy the demands of the system
design.
Fourth Embodiment
[0069] Subsequently, FIG. 8 shows an example of the fourth
embodiment of the present invention. This configuration is common
to the RF circuit for multiband switch-type antenna duplexer such
as dual band, triple band and quad band and more. The RF circuit
with the configuration of this embodiment is effective for the
system in which fT(1)<fR(2) is satisfied and fR(1) partially
overlaps fT(2) when the transmitting and receiving frequency bands
of the first system are denoted as fT(1) and fR(1) and the
transmitting and receiving frequency bands of the second system are
denoted as fT(2) and fR(2). In FIG. 8, the first system is, for
example, the GSM 850 and the second system is, for example, the
EGSM. The circuit enclosed by the dotted lines is the newly
proposed RF circuit, and the part in the parentheses is the circuit
components to be added when the quad-band or triple-band antenna
duplexer is formed.
[0070] The receive filter (EGSM) 24 for the second system is
provided. However, the receive filter (GSM 850) for the first
system is not provided. The filter (EGSM) 24 is connected in
parallel to the diode (switching element for reception) 15
connected to the output terminal for reception Rx (GSM 850), and a
first parallel connection point 7 is formed. Also, the switching
element for reception is turned on and off by the control terminal
Vcont-Rx (GSM 850). Other circuit configuration is the same as that
of the second embodiment described above. However, since the GSM
850 is the system in the United States, the filter (GSM 850) is not
always necessary in the terminal used in Europe. Therefore, it is
possible to use the switching element instead like in this circuit
configuration. If the external filter is added to the terminal Rx
(GSM 850) according to need and the positive voltage is applied to
the Vcont-Rx (GSM 850) at the time of the reception in the first
system, the function similar to the RF circuit for multiband switch
type antenna duplexer shown in FIG. 2 and others can be realized.
According to the circuit configuration, there are a lot of merits
from the aspect of the cost and mass production. For example, the
shared use of the board for the triple-band or quad-band wireless
terminal can be realized.
Fifth Embodiment
[0071] Subsequently, FIG. 9 shows an example of the fifth
embodiment of the present invention. This configuration is common
to the RF circuit for multiband switch-type antenna duplexer such
as dual band, triple band and quad band and more. The RF circuit
with the configuration of this embodiment is effective for the
system in which fT(1)<fR(2) is satisfied and fR(1) partially
overlaps fT(2) when the transmitting and receiving frequency bands
of the first system are denoted as fT(1) and fR(1) and the
transmitting and receiving frequency bands of the second system are
denoted as fT(2) and fR(2). In FIG. 9, the first system is, for
example, the GSM 850 and the second system is, for example, the
EGSM. The circuit enclosed by the dotted lines is the newly
proposed RF circuit, and the part in the parentheses is the circuit
components to be added when the quad-band or triple-band antenna
duplexer is formed.
[0072] The receive filters corresponding to the first system and
the second system are provided, and the output terminal for
reception is independently formed on the output side of the
filters. Also, on the input side, the input terminals are connected
in parallel to each other via the matching circuit and the phase
shift circuit, and a first parallel connection point 8 is formed.
The first parallel connection point 8 is connected in parallel to
the diode (switching element for reception) 10, which is connected
to the common input terminal on the transmission side corresponding
to the first and second systems, becomes conductive at the time of
the transmission in the first or second system and is released in
the reception, via the diode (switching element) 16 which is
connected to the ground via a resistor at the time of transmission
in the first system or the second system and becomes conductive at
the time of the reception and the equivalent quarter wavelength
phase shift circuit 31 and via the diode (switching element) 9
which is connected to the ground at the time of the transmission in
the first or second system and becomes conductive at the time of
the reception and the equivalent quarter wavelength phase shift
circuit 22, and the second parallel connection point 2 is formed.
Similar to the embodiments described above, the second parallel
connection point 2 is connected to the antenna terminal via the
low-frequency pass filter 21 or the high-frequency pass filter 41
or directly connected without the filter.
[0073] The configuration described above is particularly effective
for the DC demodulation system or the low IF demodulation system
whose block diagram is shown in FIG. 10. In general, in such
demodulation systems, it is necessary to perform the calibration of
the direct current offset. It is necessary to block the receiving
wave and the interfering wave incident from an antenna before this
calibration is performed. The simplest way is to apply the positive
voltage to the transmission control terminal, for example, the
Vcont-Tx (EGSM/GSM 850) of FIG. 10 at the time of waiting, thereby
putting the diode on the reception path to the ground. By doing so,
it is possible to block the incident wave from the antenna.
However, if seen from a receiver side, the impedance in the input
side from the filter, for example, the filter (GSM 850) 27 and
(EGSM) 24 is shorted out, and this state is different from the
state at the time of reception. Therefore, it is impossible to
perform the accurate calibration.
[0074] The circuit configuration shown in FIG. 9 is designed to
solve the problem above. When the positive voltage is applied to
the Vcont-Tx (EGSM/GSM 850), the diode 9 is connected to the
ground. Therefore, similar to the example shown in FIG. 2 and
others, the impedance from the second parallel connection point 2
via the equivalent quarter wavelength phase shift circuit 22
becomes the high impedance. Meanwhile, since the impedance from the
first parallel connection point 8 via the equivalent quarter
wavelength phase shift circuit 31 also becomes the high impedance,
the substantial impedance from the parallel connection point 8
becomes only the resistance via the diode 16 in an on state.
Consequently, by setting this resistance so as to be equal to the
radiation impedance of the antenna, the impedance in the input side
from the filter (GSM 850) 27 and (EGSM) 24 can be kept always
constant. As a result, the improvement of the calibration accuracy
and the performance improvement of the terminal can be
realized.
[0075] Next, FIG. 11 and FIG. 12 show an example of a resonator to
be the basis of the filter used in the present invention. FIG. 11
shows the surface acoustic wave (SAW) resonator, which is formed on
the basis of the comb-shaped electrodes (Interdigital Transducer:
IDT) on a piezoelectric substrate. FIG. 12 shows the film bulk
acoustic resonator (FBAR), which is realized by forming a
piezoelectric vibrator in a form of diaphragm on a substrate made
of Si. FIG. 13 shows the impedance characteristics of the
resonators of FIG. 11 and FIG. 12. In general, the good resonator
has the large impedance difference between the resonance frequency
fr and the antiresonance frequency fa.
[0076] FIG. 14 shows an example of the filter in which these
resonators are incorporated into a ladder-type circuit. In order to
realize the equivalent filter shown in FIG. 14 with the SAW and the
FBAR, a plurality of resonators are formed on a single chip
substrate as shown in FIG. 15 which shows the case of the SAW and
FIG. 16 which shows the case of FBAR (cross-sectional view thereof
is shown in FIG. 17). In the examples shown in FIG. 2 to FIG. 10,
the SAW filter and the FBAR filter shown in FIG. 15 and FIG. 16 are
used as the filters. Therefore, the chip-level filter can be
realized, and thus, the size of the multiband switch type antenna
duplexer can be further reduced.
[0077] Since both of the ladder type filters shown in FIG. 15 and
FIG. 16 have the single ended input and the single ended output, if
the balun circuit is introduced to the output, the balanced output
can be obtained. In particular, some SAW filters having the single
ended input and the balanced output have been developed recently,
and if such filters are used as the filters for EGSM and GSM 850 as
shown in FIG. 18, the balanced output can be obtained even if the
balun circuit is not introduced. It is evident that the present
invention includes such a combination. Also, the diode is used as
the switching element in the description above. However, a switch
made of compound semiconductor such as GaAs or a mechanical switch
such as MEMS (Micro-Electronic-Mechanical Systems) are also
available, and it is evident that the present invention includes
such a combination.
[0078] Also, the present invention is effective in the TDMA (Time
Division Multiple Access) system, for example, in the GSM system
which has become a popular mobile phone system in Europe, the
United States, China and others, and it makes a significant
contribution to the size reduction of the multiband switch type
antenna duplexer and thus the size reduction of the wireless
terminal itself.
[0079] The effect obtained by the representative one of the
inventions disclosed in this application will be briefly described
as follows.
[0080] More specifically, for a mobile phone used in the TDMA
system such as the GSM system which has been adopted in 60% or more
of the world, a multiband switch type antenna duplexer with a new
configuration necessary to achieve the multiband terminal is
provided. Consequently, the size reduction and the performance
improvement of the terminal can be realized.
* * * * *