JP2005244711A - High-frequency switching module, and communication equipment employing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To raise isolation between a low-frequency communication system and a high-frequency communication system. <P>SOLUTION: A high-frequency switching module includes: a branching filter circuit having a low-pass filter and a high-pass filter; a first switching circuit to be connected to the low-pass filter; a second switching circuit to be connected to the high-pass filter; and a low-pass filter arranged in a transmission route. The transmission line of the switching circuit which is mainly constituted of: the branching filter circuit; the LC circuit of the low-pass filter; a diode; and the transmission line, is formed in a dielectric layered body through the use of an electrode pattern. The electrode pattern constituting the LC circuit is connected to the electrode pattern constituting the transmission line via a via-hole over a plurality of dielectric body layers. The high-frequency switching module further includes ground electrodes G11, G12, G13 between via-hole electrodes Hi, Ho which connect the electrode pattern of the capacitors C2, C3, C4 constituting the high-pass filter of the branch filter to the electrode pattern of a quarter-wave transmission line at the reception route side of thee first switching circuit. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a high-frequency switch module used in a multiband cellular phone system or the like that transmits and receives signals of two or more different frequencies by sharing one antenna, and a communication apparatus using the same.

The progress of globalization of mobile phones and the like is fast, and mobile phones using a plurality of frequency bands and a plurality of communication methods have been put into practical use. For example, in Europe, UMTS (Universal Mobile Telecommunication System) is a triple of 900 MHz band EGSM (Extended Global System for Mobile Communications), 1.8 GHz band DCS (Digital Communication System), and 1.9 GHz band PCS (Personal Communication Service). Band-compatible mobile phones have been put into practical use.
Recent mobile phones prefer multiband terminals with different frequency bands and communication methods, which complicates the circuit, increasing the number of parts, increasing the size of equipment, and increasing costs. For this reason, the reduction of the number of parts and the sharing of parts are actively carried out by integrating circuits. Since antenna sharing greatly contributes to miniaturization of terminals, high-frequency switch modules that switch one antenna between multibands are important components.
As disclosed in Patent Document 1, for example, the high-frequency switch module is realized by integrating a demultiplexing circuit, a switch circuit, and a low-pass filter into a multilayer substrate made of a dielectric. Usually, an electrode material mainly composed of Ag or Cu is printed on a green sheet made of dielectric ceramic, and a capacitor constituting an LC circuit and a λ / 4 transmission line constituting a switch circuit are formed by an electrode pattern, After these green sheets are laminated in multiple layers, they are obtained by simultaneous firing at about 900 ° C. Thereafter, switching elements such as PIN diodes and FET switches and chip elements such as resistors are mounted on the multilayer substrate.

  Due to the miniaturization and high integration of the laminated substrate, the density of the electrode pattern is increasing. As a result, there is a problem in that sufficient isolation between the transmission / reception paths of each switch circuit cannot be obtained. Isolation is caused by signal leakage between different communication systems in the low frequency band and high frequency band, or signal leakage between the transmission path and the reception path in the same communication system. This is also caused by interference of electrode patterns in the laminate substrate. Therefore, in order to improve the isolation characteristics, it is necessary to consider the arrangement of the electrode patterns in the multilayer substrate. Patent Document 1 proposes that the electrode patterns of the branching circuit and the switch circuit are arranged in different regions, the λ / 4 transmission line is sandwiched between ground electrodes, and the like. Patent Document 2 proposes that a shield wall be formed in the laminate in order to prevent the influence of noise between different high-frequency circuits and mutual interference. Patent Document 3 will be described below.

Japanese Patent No. 2983016 JP-A-9-130045 Japanese Patent Laid-Open No. 2002-246942

According to Patent Document 1 and Patent Document 2, isolation characteristics can be enhanced by suppressing mutual interference between communication systems and between transmission and reception paths and leakage of unnecessary harmonics. However, further improvement in characteristics is always required.
Further, as in Patent Document 3, a high-frequency switch circuit using a GaAs-FET switch is proposed in addition to a switch circuit mainly composed of a PIN diode and a λ / 4 transmission line. In a module in which such a switch circuit is combined, interference between internal transmission lines tends to increase as the degree of integration increases. The inventors of the present invention have evaluated the characteristics, and part of the electrodes of the high-pass filter of the branching circuit interferes with part of the electrodes of the switch circuit unit connected to the low-pass filter of the branching circuit, and the insertion loss Phenomenon such as worsening of was seen. By using the method described in Patent Document 2, it is possible to prevent mutual interference of a plurality of circuits, but designing a shield wall that penetrates the laminated body is a highly integrated module. However, it is difficult to reduce the size and practical use is difficult.

  In view of the above problems, the present invention provides a high-frequency switch module capable of supporting triple bands such as EGSM (GSM850), DCS, and PCS, or higher multiband, and an electrode of a high-pass filter of a branching circuit. Interference with the electrodes of the switch circuit connected to the low-pass filter was suppressed by inserting a ground electrode between the electrodes, thereby improving insertion loss and the like. As shown in Patent Document 2, it is not necessary to design a shield wall in the laminate, and this can be realized by inserting a ground electrode in an arbitrary layer.

  The present invention relates to an antenna switch module that appropriately switches the connection between a plurality of transmission / reception transmission / reception circuits that share an antenna and have different passbands and the antenna, and demultiplexes the signals of the plurality of transmission / reception systems A demultiplexing circuit composed of a low-pass filter and a high-pass filter, a first switch circuit that is connected to the low-pass filter of the demultiplexing circuit and switches between a transmission path and a reception path, and a wide area of the demultiplexing circuit A second switch circuit that is connected to a pass filter and switches between a transmission path and a reception path, and has a low-pass filter in the transmission path of the first switch circuit and the second switch circuit, the branching circuit and the low-pass filter are: The switch circuit is mainly composed of a diode and a λ / 4 transmission line, and the branching circuit, the LC circuit of the low-pass filter, and the switch circuit. / 4 transmission line, at least part of the laminate of electrode patterns and dielectric layers, is constituted by the electrode pattern, the electrode pattern constituting the LC circuit and the electrode pattern constituting the λ / 4 transmission line are A chip element that is connected to a plurality of dielectric layers via via-hole electrodes and that constitutes a part of the diode and the LC circuit, the duplexer in the antenna switch module mounted on the laminate; This is a high-frequency switch module in which a ground electrode is provided at least partially between an electrode pattern constituting the high-pass filter and a via-hole electrode connecting the electrode pattern constituting the first switch circuit.

The electrode pattern of the capacitor or transmission line formed on the sheet of the dielectric multilayer substrate is provided over a plurality of upper and lower layers, and these are connected to each other by via-hole electrodes. Conventionally, consideration has been given to preventing interference by an electrode pattern on a sheet, but it has not reached a via-hole electrode connecting layers. The present invention pays attention to this point and aims to suppress the interference between the via hole electrode and the electrode pattern and further improve the isolation characteristics.
Specifically, between the electrode pattern of the capacitor constituting the high pass filter of the duplexer and the via hole electrode connecting the electrode pattern constituting the λ / 4 transmission line on the reception path side of the first switch circuit The ground electrode is preferably formed in a strip shape so as to separate the electrode pattern from the via hole electrode.

  According to the present invention, a high-frequency switch module having excellent isolation characteristics and low insertion loss is obtained. In addition, a communication device such as a mobile phone using the same can be provided with a small size and low power consumption.

Hereinafter, embodiments of the high-frequency switch module of the present invention will be described with reference to the drawings.
FIG. 1 shows an equivalent circuit of an EGSM, DCS, and PCS triple-band high-frequency switch module, and FIG. 2 shows an equivalent circuit of an EGSM, GSM850, DCS, and PCS quad-band high-frequency switch module. FIG. 3 is a developed view in which a sheet of a main part according to the present invention is extracted from the dielectric sheet.

First, a circuit of a triple-band high-frequency switch module will be described with reference to FIG. In FIG. 1, a duplexer Dip is composed of transmission lines L1 to L3 and capacitors C1 to C4. The transmission line L2 and the capacitor C1 form a series resonance circuit, and in the DCS band (transmission frequency: 1710 to 1785 MHz, reception frequency: 1805 to 1880 MHz) and PCS band (transmission frequency: 1850 to 1910 MHz, reception frequency: 1930 to 1990 MHz) Attenuation should be obtained. In this example, the resonance frequency is adjusted to 1.8 GHz which is substantially the center of the frequency band. The transmission line L1 is designed to have a high impedance for the frequency of the DCS / PCS system signal, and the low-pass filter F1 is configured by the transmission line L2 and the capacitor C1, and the DCS / PCS system signal is the EGSM system. Suppresses leakage into the path.
On the other hand, the transmission line L3 and the capacitor C3 form a series resonance circuit so that attenuation can be obtained in the EGSM band (transmission frequency: 880 to 915 MHz, reception frequency: 925 to 960 MHz). In this example, the resonance frequency is adjusted to 0.9 GHz which is substantially the center of the frequency band. Capacitors C2 and C4 are preferably set to relatively small capacitance values so as to have high impedance for the frequency of EGSM signals. The transmission line L3 and the capacitors C3, C2, and C4 constitute a high-pass filter F2, and EGSM signals are prevented from leaking into the DCS / PCS system.
By combining the low-pass filter circuit F1 and the high-pass filter circuit F2 described above, a branching circuit for an EGSM signal and a DCS / PCS signal is designed. The inductor Ls1 is provided as a countermeasure against static electricity.

The first switch circuit SW1 includes capacitors C5 and C6, transmission lines L5 and L6, PIN diodes D1 and D2, and a resistor R1. The lengths of the transmission lines are set so that the transmission lines L5 and L6 are λ / 4 resonators in the transmission frequency band of EGSM. However, the transmission line L5 can be replaced by a choke coil whose ground level appears to be open (high impedance state) at the EGSM transmission frequency. The resistor R1 determines the current value flowing through the first and second diodes D1 and D2 when the control power supply VC1 is in the high state. Capacitor C5 is a DC cut capacitor for the control power supply. C6 is a DC cut capacitor, and when the diode is in an ON state, the diode D2 and the capacitor C6 serve as a series resonance circuit having a resonance point at the transmission frequency of EGSM.
As described above, when the control power supply VC1 is high, both the first and second diodes D1 and D2 are turned on, and the connection point (Ho) between the second diode D2 and the transmission line L6 at the transmission frequency becomes the ground level, and λ / The impedance on the opposite side (Hi) of the transmission line L6, which is a 4-resonator, becomes infinite. Therefore, when the control power supply VC1 is High, the signal input from the EGSM_Tx port hardly leaks to the EGSM_Rx system and is transmitted to the branching circuit.
On the other hand, when the control power supply VC1 is Low, the diodes D1 and D2 are turned off, and the signal that has passed through the diplexer is hardly leaked to the EGSM Tx path and is transmitted to the EGSM_Rx port. With the above configuration, transmission / reception of the EGSM signal can be switched.

The second switch circuit SW2 includes capacitors C7 to C10, transmission lines L7 to L10, PIN diodes D3 to D6, and resistors R2 and R3. The lengths of the transmission lines are set so that the transmission lines L7 to L10 become λ / 4 resonators at the frequency of the DCS / PCS signal. However, the transmission lines L7 and L9 can be replaced by choke coils whose ground level appears to be open (high impedance state) at the DCS transmission frequency and the PCS reception frequency, respectively. The resistor R2 determines the value of the current flowing through the third and fourth diodes D3 and D4 when the control power supply VC2 is in the high state. The resistor R3 determines the value of current flowing through the fifth and sixth diodes D5 and D6 when the control power supply VC3 is in the high state. Capacitor C8 is a DC cut capacitor for control power supplies VC2 and VC3. Capacitor C7 is a DC cut capacitor, and when diodes D3 and D4 are in the ON state, diode D4 and capacitor C7 form a series resonance circuit having a resonance point at the transmission frequency in the DCS / PCS band. Similarly, when the diodes D5 and D6 are in the ON state, the capacitor C10 and the capacitor D10 become a series resonance circuit having a resonance point at the reception frequency in the PCS band.
As described above, when the control power supply VC2 is High, both the third and fourth diodes D3 and D4 are turned on, the connection point between the fourth diode D4 and the transmission line L8 is at the ground level, and the transmission is a λ / 4 resonator. The impedance on the opposite side of the line L8 becomes infinite. Therefore, when the control power supply VC2 is High, the signal input from the DCS / PCS_Tx port is hardly leaked to the DCS_Rx and PCS_Rx circuits and is transmitted to the branching circuit. Similarly, by turning on / off the power supply control VC3 while the diodes D3 and D4 are off, the DCS_Rx signal and the PCS_Rx signal input from the antenna can be transmitted with almost no leakage to other paths.
With the above configuration, it is possible to switch to DCS / PCS_Tx when the control terminal VC2 is High, to PCS_Rx when the control terminals VC2 and VC3 are Low and High, respectively, and to DCS_Rx when the control terminal VC2 and the control terminal VC3 are Low. Become.

  The first low-pass filter LPF1 is a π-type low-pass filter including a transmission line L11 and capacitors C11 to C13. Here, L11 and C11 constitute a parallel resonance circuit, and the resonance frequency is set to be twice or three times the transmission frequency of EGSM. In this embodiment, it is set around 2.7 GHz, which is about three times the transmission frequency. With the above configuration, the harmonic signal contained in the transmission signal input from the transmission signal in the EGSM band input from the power amplifier can be reduced.

  The second low-pass filter LPF2 is a π-type low-pass filter composed of a transmission line L12 and capacitors C14 to C16. Here, the transmission line L12 and the capacitor C14 constitute a parallel resonance circuit, and the resonance frequency is set to be twice or three times the DCS / PCS transmission frequency. In this embodiment, the frequency is set around 3.6 GHz, which is about twice the transmission frequency. With the above configuration, harmonic distortion included in the transmission signal input from the DCS / PCS_Tx port input from the power amplifier can be removed.

Next, the EGSM system can be further divided into GSM850 (transmission frequency: 824 to 849 MHz, reception frequency: 869 to 894 MHz) and EGSM to support quad band. An example of this is shown in FIG. The same components as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.
That is, in this example, a third switch circuit SW3 composed of a GaAs-FET switch of SPDT is provided in the subsequent stage of the reception path of the first switch circuit SW1 so as to switch between EGSM Rx and GSM850 Rx. In addition, a fourth switch circuit SW4 composed of a SPDT GaAs-FET switch is provided in the subsequent stage of the reception path of the second switch circuit SW2, so as to switch between DCS Rx and PCS Rx. At this time, control of the switch circuits SW3 and SW4 is performed by the control terminals VC3 and VC4. However, by using a circuit configuration in which the switches SW3 and SW4 are simultaneously switched, it is possible to share the power supply terminals and reduce the number of terminals. Become. According to this configuration, a high-power signal during transmission passes through a PIN diode switch with excellent power handling characteristics, so there is no distortion in the transmission signal, and the GaAs-FET switch is about +10 dBm of the received signal. Since it is used as a small-signal switching element, the power durability characteristic that was a problem of GaAs-FET switches is not a problem.
The feature of this embodiment is that the λ / 4 transmission line electrode pattern and the chip elements such as resistors necessary for the switch circuit using the PIN diode are not required, and the module can be simplified. The control power terminals VC3 and VC4 can be shared, and only four control power terminals are required. As a result, the module can be reduced in size and the control logic can be simplified.
However, when a quad-band antenna switch module that is compatible with the GSM850 system is newly designed while maintaining the shape of the conventional size, more transmission lines, etc. are built in the laminate than the triple-band antenna switch module. Therefore, there is a problem in that signal interference between the paths increases. Therefore, as described below, interference between the high frequency side electrode portion (A portion) shown in FIG. 2 and the electrode portion (B portion) of the first switch circuit is caused between the electrode portions of the present invention. It can be suppressed by inserting a ground electrode.

In the circuit of FIG. 1 or 2 described above, the LC circuit of the duplexer, the transmission line of the switch circuit, and the LC circuit of the low-pass filter are built in the dielectric laminated substrate by an electrode pattern, and a part of the switch circuit. Chip components such as PIN diodes, resistors, capacitors, inductors, GaAs-FET switches, etc., are mounted on a multilayer substrate to constitute a high-frequency switch module.
Therefore, in FIG. 3, the green sheets on which the electrode patterns related to the present invention indicated by the dotted circles A and B are extracted from the circuits of FIGS. 1 and 2 are extracted and described in detail.

Part of the green sheet 1 includes via hole electrodes Hi and Ho connected to the electrode pattern C4 of the capacitor constituting the high-pass filter F2 of the branching circuit Dip and the λ / 4 transmission line L6 of the first switch circuit SW1. A band-shaped ground electrode Gl1 bent in a bowl shape so as to separate the capacitor electrode C4 and the via-hole electrodes Hi and Ho is formed therebetween. The electrode pattern of the transmission line l6 is formed on the sheet above the green sheet 1, and the via hole electrode Hi is an input port electrode that connects the electrode pattern of the capacitor C5 and the electrode pattern of the λ / 4 transmission line L6. The electrode Ho is an output port electrode that connects the electrode pattern of the λ / 4 transmission line L6 and the diodes D1 and D2 (corresponding to a portion indicated by a dotted-line circle B in FIGS. 1 and 2). The ground electrode Gl1 is connected to the ground electrodes Gl2 and Gl3 by four via-hole electrodes, and is finally connected to the lowermost ground electrode.
Part of the green sheet 2 includes via hole electrodes Hi and Ho connected to the electrode pattern C3 of the capacitor constituting the high-pass filter F2 of the branching circuit Dip and the λ / 4 transmission line L6 of the first switch circuit SW1. Are formed respectively. Further, a belt-like ground electrode Gl2 bent in a hook shape is provided between them. The via-hole electrodes Hi and Ho are an input port electrode and an output port electrode, respectively.
Similarly, part of the green sheet 3 includes a via hole electrode Hi connected to the electrode pattern C2 of the capacitor constituting the high-pass filter F2 of the branching circuit Dip and the λ / 4 transmission line L6 of the first switch circuit SW1. , Ho are respectively formed, and a band-like ground electrode Gl3 bent in a hook shape is provided between the two. Similarly, the via-hole electrodes Hi and Ho are an input port electrode and an output port electrode, respectively.
As described above, by providing the ground electrode between the electrode pattern of the capacitor constituting the high-pass filter F2 of the branching circuit and the via hole electrode connected to the λ / 4 transmission line of the first switch circuit, It was confirmed that the isolation characteristics were improved. This is because the signal input from the GSM850 / EGSM Tx port leaks from the Hi1-3 of the λ / 4 transmission line of the first switch circuit to the high-pass filter F2 of the branching circuit. This is because the harmonic component that was originally attenuated by the series resonance circuit formed by the transmission line L2 and the capacitor C1 was not attenuated because the signal does not pass through the low-pass filter of the demultiplexing circuit. In the present invention, it is possible to improve the attenuation amount of the harmonic component by suppressing this leakage. For the same reason, the EGSM signal and GSM850 signal input from the ANT port can prevent signal leakage.
Further, by providing through holes TE1 and TE2 in the upper right part and the upper left part of Ho1 to Ho3, signal interference is suppressed not only in the electrode part of the layer but also in the through hole conducting between the layers.

In the high-frequency switch module of FIG. 2, a ground electrode and a through hole are inserted between the high-pass filter portion of the branching circuit and the switch circuit portion connected to the low-pass filter. FIG. 4 and FIG. 5 show a comparison of the characteristic data of the conventional example that did not exist. In this embodiment, the insertion loss characteristic of the ANT → EGSM Rx path is shown in FIG. 4, and the insertion loss characteristic of the DCS / PCS Tx → EGSM Rx path is shown in FIG.
The ANT → EGSM Rx path shown in FIG. 4 will be described. In a module without a ground electrode, the attenuation at 1650 MHz is about 22 dB in the ANT → EGSM Rx mode. Here, the attenuation was improved to 30 dB by creating a GND electrode and a through hole between the branching circuit and the switch circuit in the laminate. This also improved the passband insertion loss by about 0.05 dB.
Next, the DCS / PCS Tx → EGSM Rx mode shown in FIG. 5 will be described. In a module that does not have a ground electrode inserted, the attenuation at 1650 MHz is about 22 dB, and no attenuation pole is seen.Therefore, the high-frequency side of the branching circuit and the low-frequency side of the switch circuit may cause interference. Guessed. Here, when a GND electrode and a through hole were created between the branch circuit and the switch circuit in the laminate, the attenuation pole due to the series resonance circuit of the branch circuit appeared clearly, and the attenuation was greatly improved to 36 dB. I was able to.

This time, a through-hole electrode was also fabricated, but interference can be suppressed by simply inserting a GND electrode between the demultiplexing circuit and the switch circuit. If the GND electrode is made of a strip-shaped electrode, the line width of the electrode can be reduced to about 0.05 mm, so design the ground electrode with almost no change to the design pattern of other circuits. Is possible.
In the present invention, the PIN diode may be a diode having a PIN junction in which a high resistivity layer (Intrinsic layer: intrinsic semiconductor layer) is sandwiched between a P-type region and an N-type region, and is not limited to a Si type. Other material-based semiconductor diodes can also be used. Furthermore, in this embodiment, GaAs-FETs were used for SW3 and SW4, but AlGaAs, SiGe, CMOS, etc. can also be applied. For FET devices, materials and semiconductor manufacturing processes are limited. Not what you want.

  The high-frequency switch module of the present invention can be used for a communication device such as an information terminal such as a mobile phone or a PDA.

1 is an equivalent circuit diagram of a high-frequency switch module according to an embodiment of the present invention. It is the equivalent circuit schematic of the high frequency switch module of the other Example which concerns on this invention. It is the expanded view which extracted the principal part green sheet of the laminated body of the high frequency switch module which concerns on this invention. It is a figure which shows the isolation characteristic from the EGSM transmission path | route which concerns on this invention to a PCS / DCS reception path | route. It is a characteristic diagram which shows the improvement effect of the isolation from a GSM850 / EGSM transmission path to a GSM850 reception path.

Explanation of symbols

Dip: Diplexer
SW: Switch circuit
LPF: Low-pass filter circuit
L: λ / 4 transmission line
Ls: Inductor
C: Capacitor D (D1-D6): PIN diode
SW3, SW4: SPDTGaAs-FET switch

Claims (3)

A high-frequency switch module that switches an appropriate connection between a transmission circuit or a reception circuit of a plurality of transmission / reception systems that share an antenna and have different passbands,
A demultiplexing circuit comprising a low-pass filter and a high-pass filter for demultiplexing the signals of the plurality of transmission and reception systems;
A first switch circuit that is connected to the low-pass filter of the branching circuit and switches between a transmission path and a reception path;
A second switch circuit connected to the high-pass filter of the branching circuit, for switching a transmission path and a reception path;
A low-pass filter in the transmission path of the first switch circuit and the second switch circuit;
The branching circuit and the low-pass filter are configured by an LC circuit, and the switch circuit mainly includes a diode and a λ / 4 transmission line, and the branching circuit, the LC circuit of the low-pass filter, and the λ / 4 transmission line of the switch circuit At least a part of the electrode pattern and the dielectric layer is formed of the electrode pattern, and the electrode pattern constituting the LC circuit and the electrode pattern constituting the λ / 4 transmission line are composed of a plurality of dielectrics. Connected to the body layer via a via-hole electrode,
The chip element that constitutes a part of the diode and the LC circuit, in the high-frequency switch module mounted on the laminate,
A ground electrode is provided at least at a part between an electrode pattern constituting a high-pass filter of the duplexer and an electrode pattern constituting the first switch circuit. High frequency switch module. The high-frequency switch module according to claim 1, wherein the ground electrode is formed of a strip-shaped electrode pattern. A communication apparatus using the high-frequency switch module according to claim 1.

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