JP2006148975A - High frequency signal processing circuit and wireless telephone terminal using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high frequency signal processing circuit which is capable of making compatible compaction of a switch circuit and high isolation characteristics when performing switching branching a reception signal into a high frequency side signal and a low frequency side signal using a branching circuit and further which can be inexpensively configured as a whole. <P>SOLUTION: In a high frequency signal processing circuit 2, a switch element of a high frequency side switch circuit 42B which handles a high frequency side signal, between the high frequency side signal and a low frequency side signal branched by a branching circuit 44, comprises high frequency compound semiconductor transistors Tr1-Tr3, and a switch element of a low frequency side switch circuit 42A which handles the low frequency side signal, comprises PIN diodes D1, D3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a high-frequency signal processing circuit used for a radiotelephone terminal and a radiotelephone terminal using the same. Note that the wireless telephone terminal to which the present invention is applied refers to all devices that perform two-way communication using a wireless telephone network, and has a general meaning such as a mobile phone or a PHS (Personal Handy phone System). As well as wireless telephones of the above, portable terminal devices such as telephones incorporating terminal functions and portable computers having telephone line connection functions, wireless telephone line connection modems, portable computers incorporating such modems, etc. Is also included as a concept.

JP 2000-165274 A JP 2001-185902 A

  In the above radio telephone terminal, for example, a digital cellular phone, a high frequency switch is used to switch the connection between the antenna and the transmission circuit and the connection between the antenna and the reception circuit. Particularly in recent years, the number of digital mobile phones has been increasing rapidly, and new types of communication standards have been set and adopted one after another. In addition, with the increase in the number of subscriber lines, the frequency of radio waves to be used has been expanded from the original several hundred MHz band to the GHz band, and various communication wave number bands (bands) are assigned according to the communication method. .

  The communication method of the digital mobile phone is different depending on the communication company, country, or region. Of course, it is inconvenient for a user who frequently travels between areas with different communication methods to travel around, and it is inconvenient to carry a number of telephones compatible with each method. Since different communication methods may coexist, there is a desire for the same user to use different communication methods to take advantage of the individual communication methods. Therefore, in order to meet such needs, multi-band telephones that can handle transmission / reception systems of a plurality of different bands with a single telephone have been developed and are becoming popular (Patent Documents 1 and 2).

In such a multi-band telephone, a demultiplexing circuit (diplexer) that separates a received signal into a high-frequency signal and a low-frequency signal is provided, and the high-frequency signal and the low-frequency signal after demultiplexing are The transmission / reception is switched in a time division manner by the independent switch circuits.

  Conventionally, a switch circuit using a PIN diode has been used for an antenna switch of a cellular phone. In high-frequency switching using a PIN diode, the PIN diode is in a low impedance state when the control voltage is forward biased, and the PIN diode is in a high impedance state equivalent to a small-capacitance capacitor when reversely biased. . For this reason, a coil and a capacitor forming a part of the bias circuit are required around the PIN diode, and there is a drawback that the circuit becomes complicated.

  Further, at the time of reverse bias, there is a problem that the isolation characteristic is easily lost as the communication frequency increases. This is because the reactance component at the time of reverse bias derived from the capacitance of the PIN diode used in the switch circuit becomes smaller as the frequency becomes higher, and the signal easily passes through the PIN diode. Hereinafter, problems in the mobile phone will be described in detail.

  In other words, the number of mobile phone subscribers is increasing year by year, and a new frequency band is allocated in countries and regions where the number of subscribers increases and the number of subscribers increases, and services are provided in multiple frequency bands. It is supposed to be. For example, there is GSM (Global System for Mobile Communication) as one of mobile phone standards adopted all over the world. This is a method that has been generalized in Europe at first, but in recent years, the area of use has expanded significantly, and several types of GSM systems with different frequency bands and names have become prominent in each region. GSM850 is adopted in North America, and EGSM (also called GSM900) is adopted in Europe, Southeast Asia, Middle East, China, South America, and Africa. In Europe and North America, DCS (Digital Cellular System: GSM1800) and PCS (Personal Communications Service: GSM1900) having different communication frequency bands are also used in a similar manner.

  In multiband telephones, for example, GSM850 and EGSM are handled as low frequency bands, and DCS and PCS are handled as high frequency bands, whereas the former is a relatively low frequency band of less than 1 GHz. The latter is a high frequency band exceeding 1.5 GHz. If there is a frequency gap of this level and the same design PIN diode switch circuit is applied, the isolation characteristics when OFF in the latter frequency band are deteriorated by 10 dB or more compared to the values in the former frequency band. Sometimes. For this reason, in the high frequency band PIN diode switch circuit, a coil is inserted in parallel with the PIN diode to ensure isolation. Thus, a parallel resonator is formed by the capacitance of the PIN diode and the inductance of the coil, and the impedance at a desired frequency can be increased.

However, this method has the following drawbacks.
(1) When a coil for a parallel resonator is externally attached, the number of parts increases, and when the inner layer is formed in the substrate, the space occupied by the coil is large, so that the substrate size is enlarged. However, in the highly competitive mobile phone field, these represent a significant cost disadvantage. In addition, if a large coil is used as an inner layer in the board, it becomes easy to pick up noise, and it is easy to generate parasitic capacitance with other conductor layers. .
(2) Since the frequency characteristic of the parallel resonator has a notch-shaped sharp shape having a pole at the resonance frequency, the effect of increasing the impedance by narrowing in a narrow frequency band near the resonance frequency cannot be obtained. Therefore, there may be a case where a uniform isolation improvement effect cannot always be expected over the entire communication frequency band.

  The object of the present invention is to achieve both compactness of the switch circuit and high isolation characteristics when switching the received signal into a high-frequency signal and a low-frequency signal by a branching circuit, Is to provide a high-frequency signal processing circuit that can be configured at low cost, and a radiotelephone terminal using the same.

Means for Solving the Problems and Effects of the Invention

The high-frequency signal processing circuit of the present invention is a high-frequency signal processing circuit used in a radiotelephone terminal that can be switched between a plurality of communication frequency bands, and in order to solve the above problems,
An antenna side input / output terminal that is used by connecting to the antenna and shared for input and output of received and transmitted signals,
A demultiplexing circuit connected to the antenna side input / output terminal and separating the received signal received via the antenna into a high-frequency signal and a low-frequency signal;
A reception output terminal provided to handle the high frequency side signal, and outputs a demultiplexed reception signal belonging to the frequency band of the high frequency side signal from the demultiplexing circuit to the reception circuit side of the radio telephone terminal; A transmission input terminal to which a transmission output signal belonging to the frequency band of the high-frequency signal from the transmission circuit is input, and the connection between the reception output terminal and the transmission input terminal to the input / output terminal on the antenna side is switched. A high-frequency side switch circuit using a high-frequency compound semiconductor transistor as a switch element for performing
A reception output terminal that outputs a demultiplexed reception signal belonging to the frequency band of the low-frequency side signal from the demultiplexing circuit to the reception circuit side of the radiotelephone terminal, provided to handle the low-frequency side signal, A transmission input terminal to which a transmission output signal belonging to the frequency band of the low-frequency signal from the transmission circuit is input, and the connection of the reception output terminal and the transmission input terminal to the antenna side input / output terminal is switched and the switching is performed. And a low-frequency side switching circuit using a PIN diode as a switching element to be performed.

Moreover, the radio telephone terminal of the present invention includes the above-described high-frequency signal processing circuit of the present invention,
An antenna connected to the antenna side input / output terminal of the high-frequency signal processing circuit;
A band-pass filter circuit for extracting a terminal reception band and a reception circuit individually connected to a plurality of reception output terminals; and
A transmission circuit connected to the transmission input terminal;
It is provided with.

  In the present invention, among the high-frequency side signal and the low-frequency side signal separated by the branching circuit, the switch element of the high-frequency side switch circuit that handles the high-frequency side signal is configured with a high-frequency compound semiconductor transistor, The switch element of the low-frequency side switch circuit that handles the low-frequency side signal is composed of a PIN diode. A high-frequency compound semiconductor transistor can ensure good isolation characteristics in a much wider frequency range than a PIN diode switch circuit even in a high frequency band, particularly in a frequency band exceeding 1.5 GHz. In the PIN diode switch circuit, There is no need for the indispensable parallel resonator and the peripheral capacitor and coil for forming the bias circuit. Therefore, the configuration of the high-frequency side switch circuit is greatly simplified, and no external coil or inner layer is required, so the switch circuit can be made compact and high isolation characteristics can be ensured over the entire communication frequency band. Can be compatible. On the other hand, since the low frequency side switch circuit has a low signal frequency (for example, less than 1 GHz), sufficient isolation can be secured even if a circuit using a PIN diode is used. Therefore, by configuring the low-frequency side switch circuit as a PIN diode switch circuit, the number of expensive high-frequency compound semiconductor transistors used can be reduced, and the entire high-frequency signal processing circuit can be configured at low cost.

  In particular, since the low-frequency side switch circuit has a low signal frequency, compared to the high-frequency side switch circuit, the reactance at the time of OFF formed by the capacitance of the PIN diode is sufficiently high, and it is good without using a parallel resonator. Isolation characteristics can be obtained. Therefore, a configuration in which an inductor in parallel with the PIN diode is not provided can contribute to the downsizing and cost reduction of the entire low-frequency side switch circuit and thus the entire high-frequency signal processing circuit.

  Specifically, the high-frequency compound semiconductor transistor can be composed of a compound semiconductor field effect transistor. For example, GaAs field effect transistors include GaAs MESFETs (Metal-Semiconductor Field Effect Transistors) and HEMTs (High Electron Mobility Transistors), both of which are switches for transmitting and receiving signals of 800 to 3 GHz handled by radio telephone terminals. When used, both low noise and high gain of a high-frequency transmission / reception signal to be passed when ON is turned on and the isolation characteristic when OFF is cut off are extremely high, and can be used suitably in the present invention. A GaAs-based MESFET can easily integrate a plurality of elements by a monolithic IC process (for example, MMIC (Monolithic Microwave Integrated Circuit) and is effective for miniaturization of a circuit. On the other hand, a GaAs-based HEMT is a GaAs-based compound semiconductor ( This is a kind of field effect transistor using a quantum two-dimensional electron gas layer formed by a heterojunction (including AlGaAs and InGaAs) as a current channel, and has extremely high electron mobility. There is a characteristic that the index is very small and the gain is also high (for example, noise figure at 12 GHz: 0.41 dB, gain: 13 dB) As other devices, it is possible to adopt HBT (Heterobipolar Transistor). is there.

  In the high-frequency signal processing circuit of the present invention, the high-frequency side switch circuit can be configured as follows. That is, two communication frequencies that belong to the frequency band of the high frequency side signal and overlap between the terminal reception band of one communication frequency band and the terminal transmission band of the other communication frequency band A plurality of communication frequency bands including bands are handled. In addition, it has a plurality of reception output terminals individually corresponding to a plurality of communication frequencies. Each of these reception output terminals can be connected to an individual terminal reception band extracting band-pass filter circuit having a pass frequency band corresponding to the terminal reception band of each reception output terminal. The transmission input terminal is switched between the transmission connection mode in which the antenna input / output terminal is connected and the reception connection mode in which the reception output terminal is connected to the antenna input / output terminal. , One of the reception output terminals corresponding to the communication frequency band to be used is selected and connected to the antenna side input / output terminal.

  For example, in a triple-band type or quad-band type radio telephone terminal, at least the high-frequency signal among the high-frequency signal and low-frequency signal demultiplexed by the demultiplexing circuit includes a plurality of communication frequency bands. The following problems may occur when the signal is a demultiplexing signal. That is, in a multiband telephone, a received signal in a communication frequency band assigned for each method is extracted by a bandpass filter circuit. The allocated communication frequency band is generally a narrow band of about 50 to 75 MHz in order to effectively use radio resources, and the band pass filter circuit is also a narrow band filter circuit suitable for this. Here, the table shown in the middle part of FIG. 9 shows the assigned frequency bands of PCS and DCS that handle high-frequency signals of 1.5 GHz or higher. It can be seen that frequency bands that are quite close to each other are assigned. Further, when paying attention, as shown in the lower graph of the figure, the PCS terminal transmission band (Tx3) and the DCS terminal reception band (Rx4) may overlap each other in some frequency ranges. Recognize.

  In this case, when the high frequency side switch circuit is switched to the transmission side, if the isolation of the signal to the reception output terminal side in the switch is insufficient, a part of the transmission signal leaks to the reception output terminal side. . At this time, if the band of the transmission signal and the band of the reception signal are sufficiently separated, the leaked signal can be cut by a band-pass filter circuit provided on the downstream side. However, as shown in FIG. 9, when the terminal transmission band and the terminal reception band of two different bands overlap, even if a narrowband bandpass filter specialized for the terminal reception band is used, the terminal transmission band There is a problem that a transmission signal in a frequency band overlapping with the band passes through the band pass filter and flows into the receiving circuit side, leading to a malfunction.

  However, in the present invention, the switch element of the high-frequency side switch circuit is composed of a high-frequency compound semiconductor transistor with very good isolation characteristics on the high-frequency side, so that the reception output terminal of the transmission signal in the transmission connection mode Leakage to the side can be reliably prevented. As a result, even if the terminal transmission band and the terminal reception band of two different bands overlap, the transmission signal of the frequency band overlapping the terminal transmission band is received through the band-pass filter circuit for extracting the terminal reception band. Problems that flow into the circuit side and cause malfunctions can be effectively prevented.

Incidentally, in the band-pass filter circuit terminal receiving zone extraction, "having a passing frequency band corresponding to the terminal receiving band of the reception output terminal" is the width of the assigned terminal receiving band and W _S, the terminal receives band extraction high frequency side cutoff frequency f _cH of use bandpass filter _circuit, when the low frequency side cutoff frequency is f _cL, the interval _{[f cH,} f _cL] is included inside the terminal receiving band, and, J = {(F _cH −f _cL ) −W _S } / (f _cH −f _cL ) is 10% or less. This is because if J exceeds 10%, the signal extraction accuracy of the terminal reception band is impaired. In particular, when the terminal reception band width is a narrow band of about 50 to 75 MHz, the terminal reception band extraction bandpass filter circuit may be a filter circuit including a surface acoustic wave resonator. This is desirable from the viewpoint of reducing the accuracy of extracting a signal in the terminal reception band.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing an electrical configuration of a quad-band digital cellular phone (hereinafter also simply referred to as a cellular phone), which is an example of a radiotelephone terminal that handles a plurality of frequency bands. The cellular phone 1 includes an input / output interface 11 and a control microprocessor 10 as a main control unit including a CPU 12, a ROM 13 and a RAM 14 connected to the input / output interface 11. The input / output interface 11 has a well-known numeric keypad type. Are connected to a dial input unit 5 composed of push buttons, an on-hook / off-hook switch 6 for switching the mobile phone 1 between an on-hook state and an off-hook state, and a band switch 7 for switching a communication frequency band. In this embodiment, it is possible to switch between four communication systems, EGSM, GSM850, PCS, and DCS. For example, communication frequency bands (terminal reception band and terminal transmission band) assigned to PCS and DCS are as shown in FIG. The receiver 3 is connected to the monitor 15 via the amplifier 15 and the D / A converter 16, the transmitter 4 is connected to the amplifier 17 and the A / D converter 18, and the liquid crystal monitor (LCD) 19 is connected to the monitor control circuit 20. Are respectively connected to the input / output interface 11.

  A telephone connection circuit 9 is connected to the input / output interface 11. The telephone connection circuit 9 includes a first modulation unit 32A for EGSM, a first transmission unit 33A, a first reception unit 35A and a first demodulation unit 36A, a second modulation unit 32B for GSM850, a second transmission unit 33B, One receiver 35B, first demodulator 36B, third modulator 32C for PCS, third transmitter 33C, third receiver 35C and third demodulator 36C, fourth modulator 32D for DCS, fourth transmitter Unit 33D, fourth receiver 35D and fourth demodulator 36D, frequency synthesizer 34 for synthesizing a communication carrier wave at a necessary frequency, high-frequency signal processing circuit 2 according to an embodiment of the present invention, and antenna 39 connected thereto The received signal belonging to the terminal reception band in each communication frequency band is extracted from the demultiplexed reception signal demultiplexed into each band through the demultiplexing circuit 44 (FIG. 2: described later) included in the high-frequency signal processing circuit 2. Terminal receiving Band extracting band pass filter circuit 40A, 40B, 40C, configured to include a 40D or the like. Although not shown, the telephone connection circuit 9 also includes a control radio wave transmission unit for handover.

  Of the components of the telephone connection circuit 9, the parts other than the high-frequency signal processing circuit 2 are not different from general digital mobile phones and are well known, and thus detailed description thereof is omitted. The basic operation of the mobile phone 1 is the same as that of a known one, but the outline is as follows. That is, the voice input from the transmitter 4 is amplified by the amplifier 17, further digitally converted by the A / D converter 18, and then modulated by the modulation unit (32 </ b> A to 32 </ b> D) corresponding to the selected communication frequency band. Further, it is combined and amplified with the carrier wave by the transmission unit (33A or 33B), and transmitted from the high-frequency signal processing circuit 2 and the antenna 39. On the other hand, the received radio wave is received by the receiving unit (35A to 35DB) corresponding to the selected communication frequency band via the antenna 39 and the high frequency signal processing circuit 2, and after the carrier wave component is removed, the demodulating unit (36A to 36D). ) And is output from the receiver 3 via the D / A converter 16 and the amplifier 15.

  The high-frequency signal processing circuit 2 switches the reception signal and the transmission signal in a time division manner in response to a switch control signal (VC1 to VC6 described later: signal control is performed by the control microprocessor 10). On the other hand, the communication frequency band is switched by the control microprocessor 10 by operating the band selector switch 7 in this embodiment. However, the band scan is performed using the frequency synthesizer 34, and the frequency band is automatically switched to a suitable frequency band. Switching may be performed. Note that the switching processing performed by the control microprocessor 10 is mainly port switching processing of the modulation units 32A to 32D and demodulation units 36A to 36D in the input / output interface 11, instruction frequency switching processing to the frequency synthesizer 34, and the like.

  Next, FIG. 2 is a block diagram showing an electrical configuration of the high-frequency signal processing circuit 2. The high-frequency signal processing circuit 2 is used by being connected to the antenna 39 as described above, and the antenna-side input / output terminal ANT shared for input / output of the antenna reception signal and the antenna transmission signal, and the antenna-side input / output A demultiplexing circuit 44 that is connected to the terminal ANT and separates the reception signal received via the antenna 39 into the low-frequency signal 2 and the high-frequency signal 4 is provided. The low-frequency side signal 2 and the high-frequency side signal 4 that are demultiplexed by the demultiplexing circuit 44 are both a plurality of communication frequency bands, specifically, the former is GSM850 and EGSM, and the latter is PCS and DCS. It is a demultiplexed signal including each signal. A low-frequency side switch circuit 42A and a high-frequency side switch circuit 42B are provided on the output side of each demultiplexed signal.

  The high frequency side signal 4 is extracted and demultiplexed by the high pass filter circuit 46 of FIG. 2, and the low frequency side signal 4 is extracted and demultiplexed by the low pass filter circuit 45. In the present embodiment, the high-pass filter circuit 46 and the low-pass filter circuit 45 are both configured by analog filter circuits (here, LC passive filter circuits). The reception signals in each terminal reception band from the demultiplexing circuit 44 are switched by the corresponding switch circuits 42A and 42B between the transmission signals in each terminal transmission band directed from the transmission units 33A to 33D to the antenna 39.

  FIG. 3 is a circuit diagram showing details of the high-frequency signal processing circuit 2. In the demultiplexing circuit 44, the low-pass filter circuit 45 includes a capacitor C107 which forms a main part of the low-pass filter, a capacitor C108 and a coil L106 which are inserted in parallel therewith. Capacitor C108 and coil L106 constitute an LC resonance type band reject filter circuit that generates an attenuation pole on the higher frequency side than the pass band (that is, steepens the attenuation characteristic of the filter circuit). In the present embodiment, it is necessary to separate the high-frequency side signal 4 and the low-frequency side signal 2 from about 1 GHz as boundaries, and the capacitances of the capacitors C107 and C108 and the inductance of the coil L106 also have a cut-off frequency suitable for this. Adjustment is made to obtain the attenuation pole position. Basically, the capacitance of the capacitor C107 is adjusted so that the impedance is sufficiently high in the pass band and sufficiently low on the higher frequency side. On the contrary, the coil L106 sufficiently performs the adjustment function of the attenuation pole, and in order not to attenuate the signal in the pass band unnecessarily, the impedance is sufficiently low in the pass band and the impedance is sufficiently high on the higher frequency side. Adjust the inductance.

  On the other hand, the high-pass filter circuit 46 includes capacitors C207 and C208 that form the main part of the high-pass filter, and a capacitor C209 and a coil L206 that are inserted in parallel therewith. The capacitor C209 and the coil L206 constitute an LC resonance type bandpass filter circuit that generates an attenuation pole on the lower frequency side than the passband. Capacitors C207 and C208 adjust the capacitance so that the impedance is sufficiently low in the pass band and the impedance is sufficiently high on the low frequency side. On the other hand, the coil L106 adjusts the inductance so that the impedance is sufficiently high in the pass band and sufficiently low on the lower frequency side.

Each of the switch circuits 42A and 42B includes a transmission connection mode in which the transmission input terminals T _X1 T _X2 / T _X3 T _X4 are connected to the antenna side input / output terminal ANT, and reception output terminals R _X1 , R _X2 / R _X3 , R _X4 performs mutual switching between the reception connection mode connected to the antenna side input / output terminal ANT. The switch circuit 42A is used for processing the low-frequency side signal 2 and receives a reception output terminal R that outputs a reception signal to the reception circuit (reception unit 35A / 35B, demodulation unit 36A / 36B) side of the cellular phone 1 (FIG. 1). _X1 (for EGSM), R _X2 (for GSM850), transmission input terminals T _X1 T _X2 (EGSM /) to which transmission signals from the transmission circuit (modulation unit 32A / 32B, transmission unit 33A / 33B) of the cellular phone 1 are input GSM850 common use (described later) and switches the connection between the reception output terminals R _X1 and R _X2 and the transmission input terminals T _X1 T _X2 for the antenna-side input / output unit ANT. Further, the switch circuit 42B is for processing the high frequency side signal 4, and receives the received signals respectively to the receiving circuit (receiving unit 35C / 35D, demodulating unit 36C / 36D) side of the cellular phone 1 (FIG. 1). Output terminals R _X3 (for PCS), R _X4 (for DCS) and transmission input terminals T _X3 T to which transmission signals from the transmission circuit (modulation unit 32C / 32D, transmission unit 33C / 33D) of the mobile phone 1 are input _X4 (PCS / DCS shared (described later)), and switches the connection between the reception output terminals R _X3 and R _X4 and the transmission input terminals T _X3 T _X4 for the antenna-side input / output unit ANT.

The low-frequency side switch circuit 42A is configured as a PIN diode switch. That is, the switching diodes D1, D3 for individually switching the connection of the reception output terminal R _x1 (for EGSM) and the transmission input terminal T _x1 T _x2 (shared with EGSM / GSM850 (described later)) to the antenna side input / output unit ANT Are provided on the corresponding lines. These lines are provided with switching control terminals VC1 and VC3 for applying a bias voltage to the switching diodes D1 and D3, respectively, in order to control the operation of the switching diodes D1 and D3 independently. On the other hand, a resonance diode D2 combined with the switching diodes D1 and D3 is provided on the path of the reception output terminal R _x2 (for GSM850).

  Each of the diodes D1 to D3 is composed of a PIN diode, and functions as a high-frequency variable resistance element depending on the applied level of the forward bias voltage. The coils L1 and L3 provided on the terminals VC1 and VC3 form a part of the bias circuit, and are choke coils that prevent a transmission input signal from flowing backward to the VC1 to VC3 side. Further, the capacitor C2 provided on the cathode side of the resonance diode D2 also forms a part of the bias circuit and fulfills the function of noise removal. Further, the cathode side of the resonance diode D2 is grounded via the adjustment resistor R1.

When a signal is output to the reception input terminal R _x1 , the forward bias voltage to the terminal VC1 is set to a threshold value or more, and the forward bias voltage to the terminal VC3 is set to a threshold value or less. As a result, the switching diode D1 and the resonance diode D2 are resonantly coupled, and the signal passing through the reception input terminal _Rx1 is allowed (that is, the switch is turned on). On the other hand, the transmission input terminals T _x1 T _x2 are blocked from passing signals (that is, the switch is turned off). Further, when a signal is input to the transmission input terminal T _x1 T _x2 , the forward bias voltage to the terminal VC3 is set to be equal to or higher than the threshold value, and the forward bias voltage to the terminal VC2 is set to be equal to or lower than the threshold value. As a result, the switching diode D3 and the resonance diode D2 are resonantly coupled to allow signal transmission through the transmission input terminal T _x1 T _x2 and block signal transmission through the reception input terminal R _x1 . In either case, the reception output terminal R _x2 is in a state where signal passage is blocked by the resonant coupling between the switching diodes D1 to D3 and the resonance diode D2. On the other hand, when both VC1 and VC3 are equal to or lower than the threshold value, the switching diodes D1 and D3 both have high impedance, and resonance coupling with the resonance diode D2 does not occur, so that the signal passes through the reception output terminal _Rx2 . Is acceptable.

Next, the switch circuit 42B on the high frequency side includes a drain and a source on each path connecting the antenna-side input / output unit ANT, the reception output terminal R _X3 , the reception output terminal R _X4, and the transmission input terminal T _X3 T _X4. Transistors Tr1, Tr2, and Tr3 (in this embodiment, CXG1101TN of Sony Corporation are used) each composed of a connected GaAs-based MESFET (or an element obtained by monolithic a plurality of MESFETs) are provided. The switch control signals VC4, VC5, VC6 are individually input to the gates of the transistors Tr1, Tr2, Tr3. VC4, VC5, and VC6 are all binary control signals. In the transmission connection mode, only the transistor Tr3 corresponding to the transmission input terminal T _X3 T _X4 is turned on, and the others are turned off. The input state of is controlled. In the transmission connection mode, the transistors Tr1 and Tr2 corresponding to one of the reception output terminal R _X3 and the reception output terminal R _X4 are selectively turned on and the other transistors VC4, VC5, and VC6 are turned off. The input state is controlled.

2, band receiving filter circuit 40A (for EGSM: pass band 880 to 960 MHz), 40B (for GSM 850: pass band 824 to 894 MHz), 40C (for PCS: pass band 1850 to 1990 MHz), 40D. (For DCS: passband 1710 to 1880 MHz) is connected to the reception output terminals R _X1 , R _X2 , R _X3 , R _X4 , and in this embodiment, each is a narrow band filter including a surface acoustic wave resonator It is configured as a circuit. FIG. 5 shows an example of such a filter circuit, and an interdigital transducer type (hereinafter referred to as IDT type) resonator is used as a surface acoustic wave resonator. The IDT resonator uses a resonance phenomenon caused by a surface acoustic wave that propagates while reflecting / transmitting on a large number of pairs of interdigital electrodes formed on a piezoelectric ceramic plate. FIG. This band-pass filter circuit exhibits a very sharp narrow band pass characteristic in the vicinity of the resonance frequency. The surface acoustic wave resonator and the filter circuit of FIG. 5 including this are well known in the literature (Proc. IEEE, 64, 5, p. 685 (1976)). Description is omitted. Note that a narrowband filter circuit using a cavity resonator may be used instead of the IDT resonator.

Of the switch circuits 42A and 42B in FIG. 3, one provided at least on the output side of the high frequency side signal 4 of the demultiplexing circuit 44 (42A), in this embodiment the high frequency side signal 4 and the low frequency side signal. 2 and the transmission input terminals T _X1 T _X2 and T _X3 T _X4 (42A, 42B) provided on both output sides are shared in the two communication frequency bands handled by the switch circuits 42A, 42B. It is configured as a single terminal. As shown in FIG. 1, transmission signals are input to the transmission input terminals T _X1 T _X2 and T _X3 T _X4 via low-frequency amplifiers 21 and 22 for high frequencies.

The transmission input terminals T _X1 T _X2 and T _X3 T _X4 in FIG. 3 are connected to transmission low-pass filter circuits 41A and 41B having pass bands including the terminal transmission bands of these two communication frequencies. Since the frequency of the transmission side signal is synthesized by the frequency synthesizer, the band is basically narrow, and it is sufficient if background noise based on internal or external factors of the mobile phone 1 (FIG. 1) can be removed. Therefore, as shown in FIG. 1, even if the narrow band-pass filters 40A to 40D are not provided individually as in the receiving side terminals R _{X1 to} R _X4 , if the LC low-pass filter circuit is used, the background noise level is low. Can be removed sufficiently. Further, since the pass band of the LC low-pass filter circuit is relatively wide, in FIG. 3, the transmission input terminals of the two communication frequency bands are shared to form a single terminal T _X1 T _X2 and a single terminal T _X3 T _X4 , If the transmission low-pass filter circuits 41A and 41B for removing background noise are also shared, there is an advantage that the circuit configuration can be greatly simplified.

  In this embodiment, as shown in FIG. 3, the transmission low-pass filter circuits 41A and 41B are respectively similar to the low-pass filter circuit 45 of the demultiplexing circuit 44 by capacitors C101 to C103 / 201 to C203 and coils L101 / L201. It is configured. In particular, on the side of the switch circuit 42A that handles the high-frequency side signal 4, the use of the transmission low-pass filter circuit 41B has the effect of inexpensively replacing an expensive narrow-band filter circuit that includes a surface acoustic wave resonator. In addition, the coil L201 used for the higher frequency can be reduced in size, and there is an advantage that the entire circuit can be configured compactly.

  The circuit elements shown in FIG. 3 include components of a high-pass filter circuit 46 and a low-pass filter circuit 45 that form a branching circuit 44, and in this embodiment, components of transmission low-pass filter circuits 41A and 41B are shown in FIG. As described above, in the laminated body 80 in which the circuit patterns 53, 54, 55 and the dielectric layer 50 are laminated, the high frequency is formed as an inner layer in a form incorporated in the circuit patterns 53, 54, 55 and forms a switch circuit. The compound semiconductor transistor 51 for use is mounted on the surface of the multilayer body (all filters formed in the multilayer body are constituted by LC filters in this embodiment). As a result, the high-frequency signal processing circuit can be significantly reduced in size, and the occupied space in the mobile phone 1 can be greatly reduced.

  For example, when the resistor 55 (such as the resistor R1 in FIG. 3) is incorporated in the circuit, it can be formed by a meandering elongated conductor layer pattern as shown in FIG. As shown in FIG. 7, the capacitor 54 can be formed by electrode plates 54a and 54b facing each other with the dielectric layer 50 interposed therebetween. Further, the coil 53 can be formed by connecting winding patterns 53 a extending over a plurality of dielectric layers 50 through interlayer vias 59. On the other hand, the dielectric layer 50 is made of a ceramic such as glass ceramic made of lead borosilicate glass and alumina, for example. The laminate 80 is manufactured by a method in which a circuit pattern is printed on a ceramic green sheet that is a raw material of the dielectric layer 50 using a conductive paste, and is laminated and fired.

  In the present embodiment, as shown in FIG. 4, the coils 53 included in the high-pass filter circuit 46 or the low-pass filter circuits 45, 41A, 41B are at least on one side in the stacking direction of the stacked body 80, on both sides in the present embodiment. An electrode plate 56 facing the coil 53 is provided. A capacitor 54 that constitutes a constituent element of the high-pass filter circuit 46 or the low-pass filter circuits 45, 41A, and 41B is incorporated in the dielectric layer 50 located between the coil 53 and the electrode plate 56. In recent years, the laminated body 80 for high-frequency switches has been standardized in impedance as part of the integration of component standards, and the impedance level of the entire laminated body 80 is required to be adjusted to a specified value (for example, 50Ω). It has become like this. However, depending on the line width of the circuit pattern and the positional relationship of the built-in element or grounding electrode plate, a parasitic capacitance may be generated, resulting in an increase in impedance. In particular, a high-capacity parasitic capacitance tends to occur between the coil 53 that tends to have a large conductor distribution area and the large-area electrode plate 56 used for grounding or the like. Therefore, in order to adjust the impedance to the specified value, it is necessary to set the distance between the coil 53 and the electrode plate 56 to be larger than a certain value (for example, 150 μm or more) in order to reduce the parasitic capacitance. In this case, there is a problem that the dielectric layer 50 between the coil 53 and the electrode plate 56 becomes a dead space as it is, and the size of the stacked body 80 increases. This is clearly disadvantageous in the field of mobile phones, which have recently been remarkably miniaturized. Therefore, if the capacitor 54 constituting at least one of the high-pass filter circuit 46 or the low-pass filter circuits 45, 41A, and 41B is incorporated in the dielectric layer 50, the generation of dead space is eliminated, and the stacked body 80 Can be made compact.

  According to the high-frequency signal processing circuit 2 and the quad-band type mobile phone 1 using the high-frequency signal processing circuit 2, the high-frequency signal processing unit handles a high-frequency signal among the high-frequency signal and the low-frequency signal separated by the branching circuit 44 in FIG. The switch element of the band side switch circuit 42B is composed of high-frequency compound semiconductor transistors Tr1 to Tr3, and the switch element of the low band side switch circuit that handles low band side signals is composed of PIN diodes D1 and D3. High-frequency compound semiconductor transistors can ensure good isolation characteristics in a much wider frequency range than in the case of using a PIN diode switch, even in a frequency band exceeding 1.5 GHz used for PCS and DCS. A parallel resonator, a peripheral capacitor and a coil for forming a bias circuit, which are indispensable in the PIN diode switch circuit for use, are also unnecessary. Accordingly, the high-frequency side switch circuit 42B is very simple mainly composed of the transistors Tr1 to Tr3, and it is possible to achieve both compactness of the switch circuit and securing of high isolation characteristics in the entire communication frequency band. On the other hand, the low-frequency side switch circuit 42A has a signal frequency band of less than 1 GHz corresponding to GSM850 and EGSM, and even when configured as a PIN diode switch circuit, sufficient isolation can be secured. As a result, the number of expensive high-frequency compound semiconductor transistors used can be reduced, and the entire high-frequency signal processing circuit 2 can be configured at low cost.

  Further, since the high frequency side switch circuit 42B uses a GaAs-based MESFET as a switching element, in the transmission connection mode, the path leading to the reception circuit side is reliably cut off by the transistors Tr1 and Tr2 in the OFF state, and the transmission signal The isolation characteristics to the receiver circuit side are greatly improved. As a result, as already described with reference to FIG. 9, although the terminal transmission band and the terminal reception band of two different communication frequency bands (PCS / DCS) overlap, a part of the transmission signal is received by the reception circuit. There is almost no problem leaking to the side.

  The above-described embodiment has been described as an application example to a quad-band mobile phone, but it can be applied to other mobile phones having different numbers of bands, such as a triple-band mobile phone. In addition, although the MESFET is used as the high-frequency compound semiconductor transistor in the above embodiment, it may naturally be constituted by HEMT or HBT, and these transistors together with lines and other devices may be formed on a semiconductor substrate (for example, a GaAs substrate). The switch circuit may be configured as a high-frequency IC integrated in the circuit.

1 is a block diagram showing the overall configuration of a mobile phone showing an embodiment of a radiotelephone terminal of the present invention. The block diagram of the high frequency signal processing circuit. The circuit diagram which shows the detail of the high frequency signal processing circuit of FIG. The cross-sectional schematic diagram which shows an example of the structure of a laminated body. The figure which shows an example of the narrow-band filter circuit comprised including the surface acoustic wave resonator. The schematic diagram which shows the formation aspect of the resistor in a laminated body. The schematic diagram which similarly shows the formation aspect of a capacitor | condenser. The schematic diagram which similarly shows the formation aspect of a coil. Explanatory drawing of the high frequency side switch circuit which handles two communication frequency bands which overlap between one terminal receiving zone and the other terminal transmission zone.

Explanation of symbols

1 Digital mobile phone (wireless phone)
2 High-frequency signal processing circuit 32A to 32D Modulation unit (transmission circuit)
33A to 33D transmitter (transmitter circuit)
35A to 35D receiver (receiver circuit)
36A to 36D Demodulator (Receiver circuit)
39 Antenna 40A, 40B, 40C, 40D Band-pass filter circuit for terminal reception band extraction 41A, 41B Low-pass filter for transmission 42A Low-frequency side switch circuit D1, D2, D3 PIN diode 42B High-frequency side switch circuit Tr1-Tr3, 51 GaAs -Based MESFET (high frequency compound semiconductor transistor)
44 branching circuit 45 the low-pass filter circuit 46 high-pass filter circuits 53, 54, and 55 the circuit pattern 80 laminate R _X1 to R _X4 reception output terminal _{T X1 T X2, T X3 T} X4 transmitter input terminal ANT antenna side input terminal

Claims (7)

A high-frequency signal processing circuit used in a radio telephone terminal that can be switched between a plurality of communication frequency bands,
An antenna side input / output terminal that is used by connecting to the antenna and shared for input and output of received and transmitted signals,
A demultiplexing circuit that is connected to the antenna side input / output terminal and separates a reception signal received via the antenna into a high-frequency signal and a low-frequency signal;
A reception output terminal that is provided to handle the high-frequency side signal and outputs a demultiplexed reception signal belonging to the frequency band of the high-frequency side signal from the demultiplexing circuit to the reception circuit side of the radio telephone terminal; A transmission input terminal to which a transmission output signal belonging to the frequency band of the high frequency side signal from the transmission circuit of the radiotelephone terminal is input, with respect to the antenna side input / output terminal of the reception output terminal and the transmission input terminal A high-frequency side switch circuit that uses a high-frequency compound semiconductor transistor as a switching element for switching the connection, and
A reception output terminal that is provided to handle the low-frequency side signal and outputs a demultiplexed reception signal belonging to the frequency band of the low-frequency side signal from the demultiplexing circuit to the reception circuit side of the radio telephone terminal; A transmission input terminal to which a transmission output signal belonging to the frequency band of the low-frequency side signal from the transmission circuit of the wireless telephone terminal is input, and the connection between the reception output terminal and the transmission input terminal to the input / output terminal on the antenna side And a low-frequency side switch circuit using a PIN diode as a switch element for performing the switching,
A high-frequency signal processing circuit comprising: The high-frequency signal processing circuit according to claim 1, wherein a coil parallel to the PIN diode is not provided in the low-frequency side switch circuit. 3. The high-frequency signal processing circuit according to claim 1, wherein the high-frequency compound semiconductor transistor comprises a GaAs-based GaAs-based field effect transistor. The high frequency side switch circuit is
Two communication frequency bands belonging to a frequency band of the high frequency side signal, wherein there are overlaps between a terminal reception band of one communication frequency band and a terminal transmission band of the other communication frequency band It handles multiple communication frequency bands including
A plurality of reception output terminals individually corresponding to the plurality of communication frequencies;
The transmission input terminal is switched between a transmission connection mode in which the antenna input / output terminal is connected and a reception connection mode in which the reception output terminal is connected to the antenna input / output terminal. 4. In the connection mode, one of the reception output terminals corresponding to a communication frequency band to be used is selected and connected to the antenna side input / output terminal. The high-frequency signal processing circuit according to Item. The branching circuit is composed of a high-pass filter circuit and a low-pass filter circuit, and the components of the high-pass filter circuit and the low-pass filter circuit are incorporated into the circuit pattern in a laminate in which the circuit pattern and the dielectric layer are laminated. 5. The high-frequency device according to claim 1, wherein the high-frequency compound semiconductor transistor included in the high-frequency side switch circuit is mounted on a surface of the stacked body. Signal processing circuit. The transmission input terminal of the high frequency side switch circuit is configured as a single terminal that is shared in the two communication frequency bands, and the transmission input terminal includes a terminal transmission band of the two communication frequencies. 6. The high-frequency signal processing circuit according to claim 5, wherein a transmission low-pass filter circuit having a band is connected. A high-frequency signal processing circuit according to any one of claims 1 to 6,
An antenna connected to the antenna side input / output terminal of the high-frequency signal processing circuit;
A bandpass filter circuit for extracting a terminal reception band individually connected to the plurality of reception output terminals and the reception circuit;
A transmission circuit connected to the transmission input terminal;
A wireless telephone terminal characterized by comprising:

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