JP3939192B2 - Duplexer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a duplexer for selectively extracting two types of high frequency signals having different bands from a high frequency signal received by an antenna.
[0002]
[Prior art]
Conventionally, in a cellular phone, as shown in FIG. 5, a transmission system (3) and a reception system (4) are connected to an antenna (1) via an antenna duplexer (2), thereby providing one antenna (1). Is shared by the transmission system (3) and the reception system (4).
By the way, in Europe, two different band mobile phone systems, EGSM (Extended Global System for Mobile Communication) system and DCS (Digital Communication System) system, have been put into practical use. In North America, GSM (Global System for Mobile Communication) system has been put into practical use. Two different band mobile phone systems, the 850 system and the PCS (Personal Communication System) system, have been put into practical use.
Therefore, development of mobile phones that can support any band in Europe and North America is underway.
[0003]
In the case of such a multi-band mobile phone, the antenna duplexer (2) includes, as shown in FIG. 3, for example, an antenna terminal ANT to which the antenna is connected and the first and second antennas to which the transmission system is connected. 2 transmission side terminals (11), (12), and first to fourth reception side terminals (13), (14), (15), (16) to which a reception system is to be connected.
The antenna terminal ANT is connected to the antenna side terminal of the diplexer (5). The first transmission side terminal (11) is connected to the first transmission side output terminal of the diplexer (5) via the first low-pass filter (8) through which a high frequency signal in the 800 MHz band should pass, and the second transmission side terminal. (12) is connected to the second transmission-side output terminal of the diplexer (5) via a second low-pass filter (9) through which a high-frequency signal in the 1800 MHz band should pass.
The first receiving side input terminal of the diplexer (5) is connected to the first receiving side terminal (13) and the second receiving side terminal via the first demultiplexer (60) that should process a high frequency signal in the 800 MHz band. The second receiving-side output terminal of the diplexer (5) is connected to the third receiving-side terminal (15) and the second demultiplexer (70) to process a high-frequency signal in the 1800 MHz band. It is connected to the fourth receiving side terminal (16).
[0004]
The first branching filter (60) includes a ± 90 ° phase shifter (61), a first surface acoustic wave filter (62) that should pass a high-frequency signal in the 800 Hz band corresponding to the EGSM method, and a GSM850 method. It comprises a second surface acoustic wave filter (63) through which a corresponding 800 MHz band high frequency signal should pass. The second demultiplexer (70) includes a ± 90 ° phase shifter (71), a third surface acoustic wave filter (72) to pass a 1800 MHz band high frequency signal corresponding to the DCS system, and a PCS. It comprises a fourth surface acoustic wave filter (73) through which a high-frequency signal in the 1800 MHz band corresponding to the system should pass.
[0005]
In the cellular phone provided with the antenna duplexer (2), when the transmission band is 800 MHz, the transmission system is connected to the first transmission terminal (11), and when the transmission band is 1800 MHz, the transmission system is the second transmission system. Connected to the transmitting terminal (12).
In Europe, when the reception band is 800 MHz, the reception system is connected to the first reception side terminal (13), and when the reception band is 1800 MHz, the reception system is connected to the third reception side terminal (15). . On the other hand, in North America, when the reception band is 800 MHz, the reception system is connected to the second reception terminal (14), and when the reception band is 1800 MHz, the reception system is connected to the fourth reception terminal (16). .
[0006]
The phase shifter (61) of the first demultiplexer (60) operates only the first surface acoustic wave filter (62) when the received signal is a high-frequency signal in the 800 MHz band corresponding to the EGSM system. In the case of an 800 MHz band high frequency signal corresponding to the GSM850 system, only the second surface acoustic wave filter (63) is made to function. The phase shifter (71) of the second demultiplexer (70) allows only the third surface acoustic wave filter (72) to function when the received signal is a high-frequency signal in the 1800 MHz band corresponding to the DCS system. When the signal is a high-frequency signal in the 1800 MHz band corresponding to the PCS system, only the fourth surface acoustic wave filter (73) is made to function.
[0007]
For example, as shown in FIG. 6, the phase shifter (61) provided in the first duplexer (60) branches from the shared signal line (64) connected to the antenna and the shared signal line (64) to the first. A first branched signal line (65) connected to the surface acoustic wave filter (62) and a second branched signal line (66) branched from the shared signal line (64) and connected to the second surface acoustic wave filter (63). It has. A first capacitance element C1 is interposed in the first branch signal line (65), and one end of the first inductance element L1 is connected to the other end of the first inductance element L1. A second inductance element L2 is interposed in the second branch signal line 66, and one end of the second capacitance element L2 is connected to the other end of the second capacitance element L2. A third capacitance element C3 is interposed in the shared signal line (64).
The phase shifter (71) equipped in the second duplexer (70) shown in FIG. 3 has the same configuration as the phase shifter (61).
[0008]
[Problems to be solved by the invention]
FIG. 8 shows the pass characteristic of the first surface acoustic wave filter (62) by a solid line and the pass characteristic of the second surface acoustic wave filter (63) by a one-dot chain line. The bands are shifted from each other in accordance with the reception band of the EGSM system and the reception band of the GSM850 system, thereby achieving multiband correspondence.
[0009]
However, in the pass characteristic of the first surface acoustic wave filter (62), a peak P is also generated at a position shifted from the pass band to the low frequency side, and the signal attenuation is deteriorated at that frequency. Since the frequency component passes through the first surface acoustic wave filter (62) with only slight attenuation, it appears as an interference signal in the subsequent amplification circuit, and deteriorates the reception performance.
Accordingly, an object of the present invention is to provide a duplexer capable of obtaining higher reception performance than before.
[0010]
[Means for solving the problems]
As a result of intensive studies conducted by the present inventors to achieve the above object, the cause of the occurrence of the peak P on the lower frequency side of the pass band in the pass characteristics of the surface acoustic wave filter of the conventional detector is as follows. As a result, the present invention has been completed.
[0011]
That is, as shown in FIG. 6, the first surface acoustic wave filter 62 has a capacitance component C ″ in series with a capacitance component C ′ in parallel with the first branch signal line 65 between its input and output ports. The parallel capacitance component C ′ and the first inductance element L1 of the phase shifter (61) constitute an LC resonance circuit, and generate resonance at a lower frequency side than the pass band. The peak P is generated.
Therefore, in the present invention, the reception performance of the duplexer is improved by forming a trap in the pass characteristic at the resonance occurrence point and canceling the resonance.
[0012]
The duplexer according to the present invention includes a shared signal line (64), a first branch signal line (65) and a second branch signal line (66) branched from the shared signal line (64), and a first branch signal. The first capacitance element C1 interposed in the line (65), the first inductance element L1 having one end connected to the first branch signal line (65) and the other end grounded, and the first branch signal line (65) The first surface acoustic wave filter 62, the second inductance element L2 interposed in the second branch signal line 66, and the second branch signal line 66 having one end connected to the other end and grounded. The first surface acoustic wave filter (62) includes a second capacitance element C2 and a second surface acoustic wave filter (63) interposed in the second branch signal line (66). A third inductor to form a resonant circuit in combination with a series capacitance component C ″ for 65) They are connected in parallel to the scan element L3 with respect to the first surface acoustic wave filter (62).
[0013]
In the duplexer of the present invention, a first LC circuit is constituted by the first capacitance element C1 and the first inductance element L1, and a second LC circuit is constituted by the second inductance element L2 and the second capacitance element C2. Both LC circuits constitute a phase shifter (61) that gives a phase difference of ± 90 ° to the high-frequency signal received by the antenna (1).
In the duplexer, a resonant circuit is constituted by the parallel capacitance component C ′ included in the first surface acoustic wave filter (62) and the first inductance element L1 of the phase shifter (61). The series capacitance component C ″ included in the surface wave filter (62) and the third inductance element L3 form a resonance circuit having a reverse characteristic (trap characteristic) to the resonance circuit, and the resonance characteristics of the two resonance circuits are mutually different. Will be offset.
Therefore, the conventional peak generated on the lower side of the pass band of the first surface acoustic wave filter (62) is suppressed, and a sufficient amount of attenuation is obtained outside the pass band.
[0014]
【The invention's effect】
According to the duplexer according to the present invention, a sufficient attenuation amount can be obtained outside the passband, so that a higher reception performance than the conventional one can be obtained.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments in which the present invention is implemented in an antenna duplexer of a mobile phone will be specifically described below with reference to the drawings. The duplexer according to the present invention has a ceramic laminated body formed by laminating a ceramic layer made of LTCC (low temperature sintered ceramic) having a capacitance element pattern and an inductance element pattern formed on the surface, and is made into a small RF module that is modularized. This is a component and is adopted as the first duplexer (60) and the second duplexer (70) of the antenna duplexer (2) shown in FIG.
[0016]
First embodiment A first duplexer (6) of the present invention shown in FIG. 1 is branched from a shared signal line (64) connected to the diplexer (5) and the shared signal line (64). A first branched signal line (65) connected to the first surface acoustic wave filter (62) and a second branched signal line (66) branched from the shared signal line (64) and connected to the second surface acoustic wave filter (63) And has. A first capacitance element C1 is interposed in the first branch signal line (65), and one end of the first inductance element L1 is connected to the other end of the first inductance element L1. A second inductance element L2 is interposed in the second branch signal line 66, and one end of the second capacitance element C2 is connected to the other end of the second capacitance element C2. Further, a third capacitance element C3 is interposed in the shared signal line (64).
Furthermore, a third inductance element L3 is connected in parallel to the first surface acoustic wave filter (62).
[0017]
In the first duplexer (6), the first LC circuit is constituted by the first capacitance element C1 and the first inductance element L1, and the second LC circuit is constituted by the second inductance element L2 and the second capacitance element C2. Both LC circuits constitute a phase shifter (61) that gives a phase difference of ± 90 ° to the high-frequency signal received by the antenna (1).
When the received signal is an 800 MHz band high frequency signal corresponding to the EGSM system, the phase shifter (61) functions only the first surface acoustic wave filter (62), and the received signal is an 800 MHz band high frequency signal corresponding to the GSM850 system. In the case of a signal, only the second surface acoustic wave filter (63) is made to function.
[0018]
In the first duplexer (6), a resonant circuit is constituted by the parallel capacitance component C ′ included in the first surface acoustic wave filter (62) and the first inductance element L1 of the phase shifter (61). However, the first capacitance element C1 and the third inductance element L3 constitute a resonance circuit having a reverse characteristic (trap characteristic) to the resonance circuit, and the resonance characteristics of the two resonance circuits cancel each other.
Therefore, the conventional peak generated on the lower side of the pass band of the first surface acoustic wave filter (62) is suppressed, and a sufficient amount of attenuation is obtained outside the pass band.
The second duplexer (7) has the same configuration, and the same operational effects can be obtained.
[0019]
FIG. 7 shows the pass characteristic of the first surface acoustic wave filter (62) by a solid line and the pass characteristic of the second surface acoustic wave filter (63) by a one-dot chain line. The bands are shifted from each other in accordance with the reception band of the EGSM system and the reception band of the GSM850 system, thereby achieving multiband correspondence.
In the pass characteristic of the first surface acoustic wave filter (62), the conventional peak generated on the lower frequency side than the pass band is sufficiently suppressed, and sufficient attenuation is obtained outside the pass band. It has been. Therefore, when the signal that has passed through the first surface acoustic wave filter (62) is supplied to the amplifier circuit at the subsequent stage, no interference signal appears and good reception performance can be obtained.
[0020]
Second embodiment The first duplexer (6) of the present invention shown in Fig. 1 has the same configuration as the first embodiment with respect to the phase shifter (61), but the first capacitance. A third inductance element L3 is connected in parallel to the element C1.
[0021]
Also in the first duplexer (6), a resonance circuit is constituted by the parallel capacitance component C ′ included in the first surface acoustic wave filter (62) and the first inductance element L1 of the phase shifter (61). However, the first capacitance element C1 and the third inductance element L3 constitute a resonance circuit having a reverse characteristic (trap characteristic) to the resonance circuit, and the resonance characteristics of the two resonance circuits cancel each other.
Therefore, the conventional peak generated on the lower side of the pass band of the first surface acoustic wave filter (62) is suppressed, and a sufficient amount of attenuation is obtained outside the pass band.
The second duplexer (7) has the same configuration, and the same operational effects can be obtained.
[0022]
In addition, each part structure of this invention is not restricted to the said embodiment, A various deformation | transformation is possible within the technical scope as described in a claim. For example, in the present invention, as shown in FIG. 4, a changeover switch (10) is interposed between a diplexer (5) and a duplexer (60), and a first surface acoustic wave filter (62) and a second surface acoustic wave filter are provided. It is also possible to implement in the antenna duplexer (2) in which both output terminals of (63) are connected to the receiving side terminal (17) via the phase shifter (67). In this case, the duplexers (6) and (7) have an input / output relationship opposite to the configuration shown in FIGS.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a duplexer according to a first embodiment of the present invention.
FIG. 2 is a circuit diagram of a duplexer according to a second embodiment of the present invention.
FIG. 3 is a block diagram showing a configuration of an antenna duplexer.
FIG. 4 is a block diagram showing another configuration of the antenna duplexer.
FIG. 5 is a block diagram showing a configuration of a mobile phone.
FIG. 6 is a circuit diagram of a conventional duplexer.
FIG. 7 is a graph showing pass characteristics of the duplexer of the present invention.
FIG. 8 is a graph showing pass characteristics of a conventional duplexer.
[Explanation of symbols]
(1) Antenna
(2) Antenna duplexer
(3) Transmission system
(4) Reception system
(5) Diplexer
(6) Splitter
(61) Phase shifter
(62) First surface acoustic wave filter
(63) Second surface acoustic wave filter C1 First capacitance element C2 Second capacitance element L1 First inductance element L2 Third inductance element L3 Third inductance element

Claims (3)

The common signal line (64), the first branch signal line (65) and the second branch signal line (66) branching from the common signal line (64), and the first branch signal line (65) intervening in the first branch signal line (65). A capacitance element C1, a first inductance element L1 having one end connected to the first branch signal line (65) and the other end grounded, and a first surface acoustic wave filter (62) interposed in the first branch signal line (65) ), A second inductance element L2 interposed in the second branch signal line 66, a second capacitance element C2 having one end connected to the second branch signal line 66 and grounded at the other end, and a second branch A second surface acoustic wave filter (63) interposed in the signal line (66), and a series capacitance component C ″ for the first branch signal line (65) included in the first surface acoustic wave filter (62) ; The third inductance element L3, which should constitute a resonance circuit with a combination of Surface wave duplexer, characterized in that formed by connecting in parallel to the filter (62).   The first capacitance element C1 and the first inductance element L1 constitute a first LC circuit, and the second inductance element L1 and the second capacitance element C2 constitute a second LC circuit. 2. A duplexer according to claim 1, comprising a phase shifter (61) that gives a phase difference of ± 90 ° to the high-frequency signal received by (1). A phase shifter (61) that gives a phase difference of ± 90 ° to a high-frequency signal received by the antenna (1), and a first surface acoustic wave filter connected to two output ends of the phase shifter (61) ( 62) and a second surface acoustic wave filter (63), the phase shifter (61) includes a shared signal line (64) connected to the antenna (1) and the shared signal line (64). ) Branching from the first surface acoustic wave filter (62) and the second surface acoustic wave filter (63), the first branch signal line (65) and the second branch signal line (66), and the first branch signal line The first capacitance element C1 interposed in (65), the first inductance element L1 having one end connected to the first branch signal line (65) and the other end grounded, and the second branch signal line (66). the second inductance element L2, a second capacitance element C2 to which the other end is connected at one end to the second branch signal line (66) is grounded The comprising, duplexer, wherein the third inductance element L3 is connected in parallel to the first surface acoustic wave filter (62).

Images