JP2004193858A - High frequency signal processing circuit and wireless telephone terminal employing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high frequency signal processing circuit entirely configured at low cost wherein a switch circuit is effectively made compact with less power consumption in the case that a branching filter circuit separates a received signal into a high frequency signal and a low frequency signal to perform switching. <P>SOLUTION: A switch element of a high frequency switch circuit 42B processing the high frequency signal is configured with PIN diodes D1, D3 and a switch element of a low frequency switch circuit 42A processing the low frequency signal is configured with high frequency compound semiconductor transistors TR1 to TR3 in the high frequency signal and the low frequency signal separated by the branching filter circuit 44 in the high frequency signal processing circuit 2. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a high-frequency signal processing circuit used for a wireless telephone terminal and a wireless telephone terminal using the same. The wireless telephone terminal to which the present invention is applied means any device that performs 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). Wireless telephones, of course, portable terminal devices such as telephones with built-in terminal functions and portable computers with telephone line connection functions, modems for wireless telephone line connection, and portable computers with such modems. Is also included as a concept.
[0002]
[Prior art]
[Patent Document 1]
JP-A-2000-165274
[Patent Document 2]
JP 2001-185902 A
[0003]
In the above-described wireless telephone terminal, for example, a digital cellular phone, a high-frequency switch is used to switch between the connection between the antenna and the transmission circuit and the connection between the antenna and the reception circuit. In particular, in recent years, the number of spreads of digital mobile phones has rapidly increased, and new types of communication standards have been set and adopted one after another. With the increase in the number of subscriber lines, the frequency of radio waves to be used has been expanded from the initial several hundred MHz band to the GHz band, and various communication wave number bands (bands) are allocated according to communication systems. .
[0004]
The communication system of the digital mobile phone is different depending on the communication company or country or region. Naturally, it is inconvenient for a user who frequently travels back and forth between regions with different communication systems to carry around a number of telephones corresponding to each system. Since different communication systems may coexist, there is also a desire for the same user to use different communication systems to take advantage of each communication system. Therefore, in order to meet such needs, multi-band telephones capable of handling a plurality of transmission / reception systems of different bands with one telephone have been developed and are becoming widespread (Patent Documents 1 and 2).
[0005]
In such a multi-band telephone, a demultiplexing circuit (diplexer) for separating a received signal into a high-frequency signal and a low-frequency signal is provided, and the demultiplexed high-frequency signal and low-frequency signal are separated from each other. Transmission and reception are switched in a time-division manner by independent switch circuits. For example, GSM (Global System for Mobile Communication) is one of the mobile phone standards adopted worldwide. This system was initially generalized in Europe, but in recent years the area of use has been greatly expanded, and various types of GSM systems having different frequency bands and names have been found in various regions. GSM850 is used in North America, and EGSM (Extended Global System for Mobile Communication: GSM900) is used in Europe, Southeast Asia, the Middle East, China, South America, and Africa. In Europe and North America, DCS (Digital Cellular System: GSM1800) and PCS (Personal Communications Service: GSM1900) having similar communication systems but different communication frequency bands are also used. In a multi-band telephone, for example, GSM850 or EGSM is treated as a lower frequency band, and DCS or PCS is treated as a higher frequency band, whereas the latter is a high frequency band exceeding 1.5 GHz. The former is a relatively low frequency band below 1 GHz.
[0006]
[Problems to be solved by the invention]
Conventionally, a switch circuit using a PIN diode has been used for an antenna switch of a mobile phone. In high-frequency switching using a PIN diode, the fact that the PIN diode is in a low-impedance state when the control voltage is forward-biased and is in a high-impedance state equivalent to a small-capacity capacitor when the control voltage is reverse-biased is used. . 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 disadvantage that the circuit becomes complicated. In particular, a switch circuit that handles low-frequency signals needs to use a high-inductance coil as a coil used in a bias circuit, and the coil size must be large. In this case, when the coil is externally attached, the number of components increases, and when the coil is internally provided, the space occupied by the coil is large, and the size of the substrate is increased. In the highly competitive mobile phone arena, however, these are a significant cost disadvantage. In addition, if a large coil is internally formed in a substrate, problems such as easy pickup of noise and easy occurrence of parasitic capacitance with other conductor layers are likely to occur, so that design restrictions are also increased. .
[0007]
An object of the present invention is to provide a switch circuit that can effectively reduce the size of a switch circuit when switching a received signal into a high-band signal and a low-band signal by using a branching circuit. Another object of the present invention is to provide a high-frequency signal processing circuit which is small in size and can be constructed at a low cost, and a wireless telephone terminal using the same.
[0008]
[Means for Solving the Problems and Functions / Effects]
A high-frequency signal processing circuit according to the present invention is a high-frequency signal processing circuit used for a wireless telephone terminal that can be switched between a plurality of communication frequency bands.
An antenna-side input / output terminal that is used by being connected to an antenna and is used for input / output of a reception signal and a transmission signal,
A branching 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 is input, and the connection between the reception output terminal and the transmission input terminal to the antenna-side input / output terminal is switched, and A high side switch circuit using a PIN diode as a switch element for performing
A reception output terminal that is provided to handle the low-frequency side signal and 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 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 is provided, and the connection between the reception output terminal and the transmission input terminal with respect to the antenna-side input / output terminal is switched. And a low-frequency side switch circuit using a high-frequency compound semiconductor transistor as a switching element to be performed.
[0009]
Further, the wireless telephone terminal of the present invention includes the high-frequency signal processing circuit of the present invention,
An antenna connected to an antenna-side input / output terminal of the high-frequency signal processing circuit;
A terminal reception band extraction bandpass filter circuit and a reception circuit individually connected to a plurality of reception output terminals,
A transmission circuit connected to the transmission input terminal;
It is characterized by having.
[0010]
In the present invention, the switch element of the high-frequency side switch circuit that handles the high-frequency side signal among the high-frequency side signal and the low-frequency side signal separated by the demultiplexing circuit is configured by a PIN diode, The switching element of the low-frequency side switching circuit that handles signals is configured by a compound semiconductor transistor for frequency. High-frequency compound semiconductor transistors can secure good isolation characteristics over a wide frequency range in the high-frequency band, and do not require parallel resonators, which are essential for PIN diode switch circuits, and peripheral capacitors and coils for forming bias circuits. is there. Therefore, the configuration of the low-frequency side switch circuit is greatly simplified, and since the frequency is low (for example, less than 1 GHz), the external mounting of the coil and the inner layer on the substrate, which have been forced to be large, are not required. The size of the side switch circuit can be reduced. On the other hand, since the high-frequency side switch circuit has a high signal frequency (for example, less than 1 GHz), when a high-frequency compound semiconductor transistor having a low impedance at the time of conduction is used for the switching element, power consumption increases and heat generation of the switch part also increases. Because it is likely to occur, heat dissipation measures may need to be strengthened. Therefore, by configuring the high-frequency side switch circuit as a PIN diode switch circuit, it is possible to reduce power consumption and suppress heat generation. In addition, by using expensive high-frequency compound semiconductor transistors in the low-frequency side switch circuit, the entire high-frequency signal processing circuit can be configured at low cost.
[0011]
The high-frequency compound semiconductor transistor can be specifically composed of a compound semiconductor field-effect transistor. For example, GaAs-based field-effect transistors include GaAs-based MESFETs (Metal-Semiconductor Field Effect Transistors) and HEMTs (High-Electron Mobility Transistors). When used, both low noise and high gain of a high frequency transmission / reception signal to be passed when ON is conducted can be achieved, and the isolation characteristics when OFF is cut off are extremely high. A GaAs-based MESFET is easy to integrate a plurality of elements by a monolithic IC process (for example, MMIC (Monolithic Microwave Integrated Circuit), and is also effective for miniaturization of a circuit. On the other hand, a GaAs-based HEMT is a GaAs-based compound semiconductor (AlGaAs). , And InGaAs), a kind of field-effect transistor using a quantum two-dimensional electron gas layer formed by a heterojunction as a current channel, and having extremely high electron mobility. (E.g., a noise figure at 12 GHz: 0.41 dB, gain: 13 dB), and an HBT (Heterobipolar Transistor) as another device. To be possible.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram illustrating an electrical configuration of a quad-band digital mobile phone (hereinafter, also simply referred to as a mobile phone), which is an example of a wireless telephone terminal that handles a plurality of frequency bands. The mobile phone 1 has an input / output interface 11 and a control microprocessor 10 as a main control unit composed of a CPU 12, a ROM 13, a RAM 14, and the like connected thereto. , 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 the present embodiment, switching between the four communication systems of EGSM, GSM850, PCS and DCS is possible. Communication frequency bands (terminal reception band and terminal transmission band) allocated to each system are as shown in FIGS. 9 and 10. The receiver 3 is connected via an amplifier 15 and a D / A converter 16, the transmitter 4 is connected via an amplifier 17 and an A / D converter 18, and a liquid crystal monitor (LCD) 19 controls a monitor control circuit 20. Are respectively connected to the input / output interface 11.
[0013]
The input / output interface 11 is connected to a telephone connection circuit 9. The telephone connection circuit 9 includes a first modulator 32A for EGSM, a first transmitter 33A, a first receiver 35A and a first demodulator 36A, a second modulator 32B for GSM850, a second transmitter 33B, One receiving unit 35B and first demodulating unit 36B, third modulating unit 32C for PCS, third transmitting unit 33C, third receiving unit 35C and third demodulating unit 36C, fourth modulating unit 32D for DCS, fourth transmitting Unit 33D, a fourth receiving unit 35D and a fourth demodulating unit 36D, a frequency synthesizer 34 for synthesizing a communication carrier at a required frequency, a high-frequency signal processing circuit 2 according to an embodiment of the present invention, and an antenna 39 connected thereto. A reception signal belonging to a terminal reception band in each communication frequency band is extracted from a demultiplexed reception signal divided into each band through a demultiplexing circuit 44 (FIG. 2: described later) included in the high-frequency signal processing circuit 2. Terminal receiver 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 transmitter for handover.
[0014]
The components other than the high-frequency signal processing circuit 2 among the components of the telephone connection circuit 9 are well known and are not different from general digital mobile phones, and thus detailed description is omitted. The basic operation of the mobile phone 1 is the same as that of the well-known one, but the outline is as follows. That is, the voice input from the transmitter 4 is amplified by the amplifier 17, and is further digitally converted by the A / D converter 18, and then modulated by the modulators (32 A to 32 D) corresponding to the selected communication frequency band. Then, the signal is further combined and amplified with the carrier 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 waves are received by the receivers (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 components are removed, the demodulators (36A to 36D). ) Is demodulated into a digital audio signal and output from the receiver 3 via the D / A converter 16 and the amplifier 15.
[0015]
The high-frequency signal processing circuit 2 switches between a reception signal and a 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, in the present embodiment, the switching of the communication frequency band is performed by the control microprocessor 10 by operating the band changeover switch 7. However, the band scan is performed using the frequency synthesizer 34, and the communication frequency band is automatically switched to the appropriate frequency band. Switching may be performed. Note that the switching process performed by the control microprocessor 10 is mainly a port switching process of the modulation units 32A to 32D and the demodulation units 36A to 36D in the input / output interface 11, a designated frequency switching process to the frequency synthesizer 34, and the like.
[0016]
Next, FIG. 2 is a block diagram illustrating 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 includes an antenna-side input / output terminal ANT used for input / output of an antenna reception signal and an antenna transmission signal; A branching circuit 44 connected to the terminal ANT and separating a reception signal received via the antenna 39 into a low-frequency signal (2) and a high-frequency signal (4) is provided. The low-frequency side signal (2) and the high-frequency side signal (4), which are demultiplexed by the demultiplexing circuit 44, are respectively in a plurality of communication frequency bands, specifically, the former is GSM850 and EGSM, and the latter is PCS. And DCS. 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.
[0017]
The high band side signal {circle around (4)} is extracted and demultiplexed by the high pass filter circuit 46 of FIG. 2, and the low band side signal is extracted and demultiplexed by the low pass filter circuit 45. In the present embodiment, each of the high-pass filter circuit 46 and the low-pass filter circuit 45 is configured by an analog filter circuit (here, an LC passive filter circuit). The received signal of each terminal reception band from the demultiplexing circuit 44 is switched between the transmission signal of each terminal transmission band from each of the transmission units 33A to 33D toward the antenna 39 by the corresponding switch circuits 42A and 42B.
[0018]
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 is a main part of the LC low-pass filter, and a capacitor C108 and a coil L106 inserted in parallel with the capacitor C107. The capacitor C108 and the coil L106 form an LC resonance type band reject filter circuit that generates an attenuation pole on a higher frequency side than the pass band (that is, sharpens the attenuation characteristic of the filter circuit). In the present embodiment, it is necessary to separate the high-frequency signal (4) and the low-frequency signal (2) around a boundary of about 1 GHz, and the capacitances of the capacitors C107 and C108 and the inductance of the coil L106 also conform to this. The cutoff frequency and the position of the attenuation pole are adjusted so as to be obtained. 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 high frequency side. Conversely, the coil L106 sufficiently performs the function of adjusting the attenuation pole and has a sufficiently low impedance in the pass band and a sufficiently high impedance on the higher frequency side so as not to unnecessarily attenuate the signal in the pass band. Adjust the inductance.
[0019]
On the other hand, the high-pass filter circuit 46 includes capacitors C207 and C208, which are main parts of the LC high-pass filter, and a capacitor C209 and a coil L206 inserted in parallel with the capacitors C207 and C208. The capacitor C209 and the coil L206 constitute an LC resonance type band-pass filter circuit that generates an attenuation pole on the lower frequency side than the pass band. The capacitance of the capacitors C207 and C208 is adjusted so that the impedance is sufficiently low in the pass band and sufficiently high on the lower frequency side. On the other hand, the inductance of the coil L106 is adjusted so that the impedance is sufficiently high in the pass band and sufficiently low on the lower frequency side.
[0020]
Each of the switch circuits 42A and 42B has a transmission input terminal T _X1 T _X2 / T _X3 T _X4 Is connected to the antenna-side input / output terminal ANT, and the reception output terminal R _X1 , R _X2 / R _X3 , R _X4 Performs mutual switching between a reception connection mode connected to the antenna side input / output terminal ANT. The switch circuit 42A is for processing the low-frequency side signal {circle around (2)}, and is a reception output for outputting a reception signal to the reception circuit (reception unit 35A / 35B, demodulation unit 36A / 36B) side of the mobile phone 1 (FIG. 1). Terminal R _X1 (For EGSM), R _X2 (For GSM850), a transmission input terminal T to which a transmission signal from a transmission circuit (modulation unit 32A / 32B, transmission unit 33A / 33B) of the mobile phone 1 is input. _X1 T _X2 (Common to EGSM / GSM850 (described later)), and a reception output terminal R for the antenna-side input / output unit ANT. _X1 , R _X2 And transmission input terminal T _X1 T _X2 The connection is switched. The switch circuit 42B is for processing the high frequency side signal {circle around (4)}, and outputs the received signal to the receiving circuit (receiving unit 35C / 35D, demodulating unit 36C / 36D) side of the mobile phone 1 (FIG. 1). Receiving output terminal R _X3 (For PCS), R _X4 (For DCS) and a transmission input terminal T to which transmission signals from transmission circuits (modulation units 32C / 32D, transmission units 33C / 33D) of the mobile phone 1 are input. _X3 T _X4 (PCS / DCS shared (described later)), and a reception output terminal R for the antenna-side input / output unit ANT. _X3 , R _X4 And transmission input terminal T _X3 T _X4 The connection is switched.
[0021]
The low band side switch circuit 42A includes an antenna side input / output unit ANT and a reception output terminal R _X1 , Reception output terminal R _X2 And transmission input terminal T _X1 T _X2 Tr1, Tr2, Tr3 composed of a GaAs-based MESFET (or a monolithic element of a plurality of MESFETs) in which the drain and the source are connected on each path connecting the CXG1101TN of Sony Corporation in this embodiment. Are provided, and switch control signals VC1, VC2, and VC3 are individually input to the gates of the transistors Tr1, Tr2, and Tr3. VC1, VC2 and VC3 are binary control signals, and in the transmission connection mode, the transmission input terminal T _X3 T _X4 , The input states of VC1, VC2 and VC3 are controlled so that only the transistor Tr3 corresponding to is turned on and the others are turned off. In the transmission connection mode, the reception output terminal R _X1 And reception output terminal R _X2 The input states of VC1, VC2, and VC3 are controlled such that the transistor Tr1 or the transistor Tr2 corresponding to one of them is selectively turned on, and the other is turned off.
[0022]
Next, the high frequency side switch circuit 42B is configured as a PIN diode switch. That is, the reception output terminal R _x3 (For PCS) and transmission input terminal T _x3 T _x4 Switching diodes D1 and D3 for individually switching the connection to the antenna-side input / output unit ANT with (PCS / DCS shared (described later)) are provided on the corresponding lines. In these lines, switching control terminals VC4 and VC6 for applying a bias voltage to the switching diodes D1 and D3 respectively are provided in a branched manner in order to independently control the operation of the switching diodes D1 and D3. On the other hand, the reception output terminal R _x4 On the (DCS) path, a resonance diode D2 combined with the switching diodes D1 and D3 is provided.
[0023]
Each of the diodes D1 to D3 is formed of a PIN diode, and functions as a high-frequency variable resistance element according to the applied level of a forward bias voltage. The coils L1 and L3 provided on the terminals VC4 and VC6 form a part of a bias circuit, and are choke coils for preventing a transmission input signal from flowing back to the VC1 to VC3. The capacitors C1 and C3 also form part of a bias circuit, and perform a function of removing noise. Further, in order to improve the isolation characteristics, coils L301 and L302 are connected in parallel with the switching diodes D1 and D3. The capacitor C2 provided on the cathode side of the resonance diode D2 also forms a part of the bias circuit, and performs a function of removing noise. The cathode side of the resonance diode D2 is grounded via the adjustment resistor R1.
[0024]
Receive input terminal R _x3 When a signal is output to the terminal VC4, the forward bias voltage to the terminal VC4 is set to a threshold or more, and the forward bias voltage to the terminal VC6 is set to a threshold or less. As a result, the switching diode D1 and the resonance diode D2 are resonantly coupled, and the reception input terminal R _x3 Is allowed (that is, the switch is turned ON). On the other hand, the transmission input terminal T _x3 T _x4 Is interrupted (that is, the switch is turned off). Also, the transmission input terminal T _x3 T _x4 When a signal is input to the terminal VC6, the forward bias voltage to the terminal VC6 is set to a threshold or more, and the forward bias voltage to the terminal VC4 is set to a threshold or less. As a result, the switching diode D3 and the resonance diode D2 are resonantly coupled, and the transmission input terminal T _x3 T _x4 Is allowed to pass through, and the reception input terminal R _x3 Signal is blocked. In any case, the reception output terminal R _x4 Is in a state where signal passage is blocked by the resonance coupling between the switching diodes D1 to D3 and the resonance diode D2. On the other hand, when both VC4 and VC6 are equal to or lower than the threshold value, the switching diodes D1 and D3 both have high impedance, and no resonance coupling with the resonance diode D2 occurs. _x4 Is allowed to pass through.
[0025]
2, the terminal reception band extraction band-pass 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: pass band 1710 to 1880 MHz) _X1 , R _X2 , R _X3 , R _X4 In this embodiment, each is configured as a narrow band filter circuit including a surface acoustic wave resonator. FIG. 5 shows an example of such a filter circuit, in which an interdigital transducer type (hereinafter abbreviated as IDT type) resonator is used as a surface acoustic wave resonator. The IDT resonator utilizes a resonance phenomenon caused by a surface acoustic wave propagating while being reflected and transmitted on a large number of pairs of interdigital transducers formed on a piezoelectric ceramic plate. Has a very sharp narrow bandpass characteristic near its resonance frequency. The surface acoustic wave resonator and the filter circuit itself shown in FIG. 5 including the same are known in the literature (Proc. IEEE, 64, 5, p. 685 (1976)). Description is omitted. Note that, instead of the IDT resonator, a narrow band filter circuit using a cavity resonator may be used.
[0026]
Note that, 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), and in the present embodiment, the high-frequency side signal (4) The transmission input terminals T (42A, 42B) provided on both output sides of the low-frequency side signal (2) _X1 T _X2 And T _X3 T _X4 Are configured as a single terminal shared in two communication frequency bands handled by the switch circuits 42A and 42B. As shown in FIG. 1, each transmission input terminal T _X1 T _X2 , T _X3 T _X4 The transmission signal is input through the high-frequency low-noise amplifiers 21 and 22.
[0027]
Transmission input terminal T _X1 T _X2 , T _X3 T _X4 Are connected to transmission low-pass filter circuits 41A and 41B having a pass band including the terminal transmission bands of the two communication frequencies. Since the frequency of the signal on the transmission side is synthesized by the frequency synthesizer, the band is basically narrow, and it is sufficient to remove background noise due to internal or external factors of the mobile phone 1 (FIG. 1). Therefore, the receiving terminal R in FIG. _X1 ~ R _X4 Even if the narrow bandpass filters 40A to 40D are not individually provided as in the above, the use of the LC low-pass filter circuit can sufficiently remove the low-level background noise. Furthermore, since the pass band of the LC low-pass filter circuit is relatively wide, as shown in FIG. _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 shared, there is an advantage that the circuit configuration can be greatly simplified. In the present embodiment, the transmission low-pass filter circuits 41A and 41B are configured similarly to the low-pass filter circuit 45 of the demultiplexer circuit 44 by the capacitors C101 to C103 / 201 to C203 and the coils L101 / L201.
[0028]
The circuit elements shown in FIG. 3 are components of a high-pass filter circuit 46 and a low-pass filter circuit 45 forming a demultiplexing circuit 44. In this embodiment, components of the 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 laminated body 80 is formed by being embedded in the circuit patterns 53, 54, 55 and forming a switch circuit. The structure is such that the compound semiconductor transistor for use 51 is mounted on the surface of the multilayer body (in the present embodiment, the filters inside the multilayer body are all constituted by LC filters). As a result, the size of the high-frequency signal processing circuit can be significantly reduced, and the space occupied in the mobile phone 1 (FIG. 1) can be significantly reduced.
[0029]
For example, when the resistor 55 (such as the resistor R1 in FIG. 3) is incorporated in a 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 facing electrode plates 54a and 54b with the dielectric layer 50 interposed therebetween. Further, the coil 53 can be formed in such a manner that the winding pattern 53 a extending over the plurality of dielectric layers 50 is connected by the interlayer via 59. On the other hand, the dielectric layer 50 is made of, for example, a ceramic such as a glass ceramic made of lead borosilicate glass and alumina. The laminate 80 is manufactured by a method in which a circuit pattern is printed on a ceramic green sheet as a raw material of the dielectric layer 50 by using a conductive paste to form a thick film, laminated, and fired.
[0030]
In the present embodiment, as shown in FIG. 5, at least one side of the coil 53 included in the high-pass filter circuit 46 or the low-pass filter circuits 45, 41A, 41B in the stacking direction of the stacked body 80, and in this embodiment, both sides. An electrode plate 56 facing the coil 53 is provided. Then, a capacitor 54 which is a component of the high-pass filter circuit 46 or the low-pass filter circuits 45, 41A, 41B is incorporated in the dielectric layer 50 located between the coil 53 and the electrode plate 56. In recent years, the unification of the impedance of the laminated body 80 for a high-frequency switch has been promoted as a part of the integration of component standards, and it is obligatory to adjust the impedance level of the entire laminated body 80 to a specified value (for example, 50Ω). It is becoming. However, depending on the line width of the circuit pattern and the positional relationship of the fabricated element or the grounding electrode plate, parasitic capacitance may occur and impedance may increase. In particular, high-capacitance parasitic capacitance is likely to occur between the coil 53 where the conductor distribution area tends to be large and the large-area electrode plate 56 used for grounding or the like. Therefore, in order to adjust the impedance to a specified value, it is necessary to set the distance between the coil 53 and the electrode plate 56 to a certain value or more (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 and the size of the laminated body 80 becomes large. This is clearly disadvantageous in the field of portable telephones, which have been remarkably reduced in size in recent years. Therefore, if a capacitor 54 constituting at least one of the high-pass filter circuit 46 and the low-pass filter circuits 45, 41A and 41B is incorporated in the dielectric layer 50, the occurrence of dead space is eliminated, and the stacked body 80 Can be made more compact.
[0031]
According to the high-frequency signal processing circuit 2 of FIG. 3 and the quad-band mobile phone 1 (FIG. 1) using the same, the switching elements of the low-frequency side switch circuit 42A are constituted by high-frequency compound semiconductor transistors Tr1 to Tr3, The switch element of the high-frequency side switch circuit was constituted by PIN diodes D1 and D3. High-frequency compound semiconductor transistors can secure good isolation characteristics over a wide frequency range in the high-frequency band, and do not require parallel resonators, which are essential for PIN diode switch circuits, and peripheral capacitors and coils for forming bias circuits. is there. Accordingly, the configuration of the low-frequency side switch circuit 42A is greatly simplified, and since the frequency is low (less than 1 GHz), the external mounting of the coil and the inner layer on the substrate, which have been forced to be large, are not required. The low-frequency side switch circuit 42A can be made compact. On the other hand, since the high-frequency side switch circuit 42B has a high signal frequency (exceeding 1.5 GHz), when a high-frequency compound semiconductor transistor having a low impedance at the time of conduction is used for the switching element, power consumption increases, and the switching section has It is easy to generate heat. However, in the present embodiment, by configuring the high-frequency side switch circuit 42B as a PIN diode switch circuit, it is possible to reduce power consumption and suppress heat generation. In addition, by using expensive high-frequency compound semiconductor transistors in the low-frequency side switch circuit 42A, the entire high-frequency signal processing circuit 2 can be configured at low cost.
[0032]
Although the embodiment described above has been described as an example of application to a quad-band mobile phone, it is of course applicable to other mobile phones having different numbers of bands, such as a triple-band mobile phone. Further, although the MESFET is used as the high-frequency compound semiconductor transistor in the above-described embodiment, it is needless to say that the transistor may be constituted by HEMT or HBT, and these transistors may be formed on a semiconductor substrate (for example, a GaAs substrate) together with lines and other devices. The switch circuit may be configured as a high-frequency IC integrated in the IC.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an overall configuration of a mobile phone showing one embodiment of a wireless telephone terminal of the present invention.
FIG. 2 is a block diagram of the high-frequency signal processing circuit.
FIG. 3 is a circuit diagram showing details of the high-frequency signal processing circuit of FIG. 2;
FIG. 4 is a schematic cross-sectional view illustrating an example of the structure of a laminate.
FIG. 5 is a diagram illustrating an example of a narrow-band filter circuit including a surface acoustic wave resonator.
FIG. 6 is a schematic view showing a state in which a resistor is formed in a laminate.
FIG. 7 is a schematic view showing a manner of forming a capacitor.
FIG. 8 is a schematic view showing a manner of forming a coil.
[Explanation of symbols]
1. Digital mobile phones (wireless telephone terminals)
2 High frequency signal processing circuit
32A to 32D modulation unit (transmission circuit)
33A to 33D transmission unit (transmission circuit)
35A to 35D receiving unit (receiving circuit)
36A to 36D demodulation unit (receiving 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 to Tr3, 51 GaAs MESFET (high frequency compound semiconductor transistor)
44 demultiplexing circuit
45 Low-pass filter circuit
46 High-pass filter circuit
53,54,55 circuit pattern
80 laminate
R _X1 ~ R _X4 Receive output terminal
T _X1 T _X2 , T _X3 T _X4 Transmission input terminal
ANT antenna input / output terminal

Claims (4)

A high-frequency signal processing circuit used in a wireless telephone terminal switchable between a plurality of communication frequency bands,
An antenna-side input / output terminal that is used by being connected to an antenna and is used for input / output of a reception signal and a transmission signal,
A branching 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 for handling the high-frequency side signal, and that outputs a demultiplexed reception signal belonging to a frequency band of the high-frequency side signal from the demultiplexing circuit to a reception circuit side of the wireless telephone terminal. A transmission input terminal to which a transmission output signal belonging to a frequency band of the high-frequency side signal from the transmission circuit of the radio telephone terminal is input, and the reception output terminal and the transmission input terminal of the antenna side input / output terminal A high-frequency side switch circuit that switches a connection and uses a PIN diode as a switch element for performing the switching;
A reception output terminal that is provided for handling the low-frequency signal and that outputs a demultiplexed reception signal belonging to a frequency band of the low-frequency signal from the demultiplexing circuit to a reception circuit side of the wireless telephone terminal; A transmission input terminal to which a transmission output signal belonging to a frequency band of the low-frequency side signal from the transmission circuit of the wireless telephone terminal is input, and connection of the reception output terminal and the transmission input terminal to the antenna-side input / output terminal And a low-frequency switch circuit using a high-frequency compound semiconductor transistor as a switch element for performing the switching,
A high-frequency signal processing circuit comprising: 2. The high-frequency signal processing circuit according to claim 1, wherein said high-frequency compound semiconductor transistor comprises a GaAs-based GaAs-based field-effect transistor. The demultiplexing circuit includes a high-pass filter circuit and a low-pass filter circuit, and components of the high-pass filter circuit and the low-pass filter circuit are incorporated in the circuit pattern in a laminate in which a circuit pattern and a dielectric layer are laminated. 4. The high-frequency device according to claim 1, wherein the high-frequency compound semiconductor transistor included in the low-frequency side switch circuit is mounted on a surface of the stacked body. 5. Signal processing circuit. A high-frequency signal processing circuit according to any one of claims 1 to 3,
An antenna connected to the antenna-side input / output terminal of the high-frequency signal processing circuit;
A terminal reception band extraction band-pass filter circuit and the reception circuit individually connected to the plurality of reception output terminals,
A transmission circuit connected to the transmission input terminal;
A wireless telephone terminal comprising:

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