JP2004193881A - High frequency signal processing circuit and wireless phone terminal employing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high frequency signal processing circuit which can obtain an extracted waveform from a filtered high frequency component of a received signal advantageous to improve the quality of an extracted signal of an operating frequency band and which can thereby contribute to improvement of the communication quality of a wireless phone communication apparatus. <P>SOLUTION: The switch circuits 42A, 42B of the high frequency signal processing circuit 2 deal with a plurality of communication frequency bands including two communication frequency bands each having a frequency band overlapping one terminal reception band and the other terminal transmission band. Connection of band pass filter circuits for extracting respective terminal reception bands each having a pass frequency band corresponding to the terminal reception band of each of reception/output terminals R<SB>x1</SB>to R<SB>x4</SB>is scheduled to each of the reception/output terminals R<SB>x1</SB>to R<SB>x4</SB>each provided to the communication frequency bands. Switching elements used for switching between a transmission connection mode and a reception connection mode are composed of high frequency compound semiconductor transistors Tr1 to Tr6. <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 2000-165274 A [Patent Document 2]
JP 2001-185902 A
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]
[Problems to be solved by the invention]
By the way, the number of mobile phone subscribers is increasing, and a new frequency band is allocated in a country or a region where the line tends to be short due to the increase in the number of subscribers, and services are provided in a plurality of frequency bands. It has become. 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. For example, 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. The same occurs in DCS (Digital Cellular System: GSM1800) and PCS (Personal Communications Service: GSM1900) having similar communication schemes but different communication frequency bands.
[0006]
In a multi-band telephone, a reception signal in a communication frequency band assigned for each system is extracted by a band-pass filter circuit. The allocated communication frequency band is generally set to a narrow band of about 50 to 75 MHz in order to effectively utilize radio wave resources, and a narrow band filter circuit suitable for the band pass filter circuit is used as the band pass filter circuit. Here, the table shown in the middle part of FIG. 9 shows the allocated frequency bands of EGSM and GSM850, and the table shown in the middle part of FIG. 10 shows the allocated frequency bands of PCS and DCS. Is assigned. Further, if further attention is paid, as shown in the lower graph of each figure, the terminal transmission band (Tx1) of the EGSM and the terminal reception band (Rx2) of the GSM850, and the terminal transmission band (Tx3) of the PCS and the DCS It can be seen that the terminal reception bands (Rx4) of each overlap each other in some frequency ranges.
[0007]
By the way, mobile phone communication is a type of frequency division multiplexing bidirectional communication in which a terminal transmission band and a terminal reception band are set so as not to overlap with each other. As long as the reception bands do not overlap, the transmission signal and the reception signal of each band can be separated without any trouble. In an actual telephone, since the antenna is shared between the transmitting circuit and the receiving circuit, transmission and reception are performed by switching the connection between the transmitting circuit and the receiving circuit and the antenna in a time-division manner with an antenna switch.
[0008]
Then, when the antenna switch 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 leak signal can be cut by the band-pass filter circuit provided on the downstream side. However, as shown in FIG. 9 or FIG. 10, when the terminal transmission band and the terminal reception band of two different bands overlap, even if a narrow band bandpass filter specialized for the terminal reception band is used. However, there is a problem that a transmission signal in a frequency band overlapping with the terminal transmission band passes through the band-pass filter, flows into the receiving circuit side, and causes a malfunction or the like.
[0009]
SUMMARY OF THE INVENTION An object of the present invention is to provide a radio telephone terminal that handles a plurality of communication frequency bands close to each other, which can effectively prevent a malfunction of a receiving circuit based on an overlap between a terminal transmission band and a terminal reception band of two different bands. An object of the present invention is to provide a signal processing circuit and a wireless telephone terminal using the same.
[0010]
[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 in a wireless telephone communication terminal (hereinafter, also referred to as a multi-band terminal) that can be switched between a plurality of communication frequency bands. To
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 transmission input terminal to which a transmission signal from an individual transmission circuit provided for each communication frequency band is provided in the wireless telephone terminal, and a reception signal from the antenna are provided for each communication frequency band in the wireless telephone terminal. A transmission connection mode in which a plurality of reception output terminals for outputting to an individual reception circuit side are provided, and a transmission input terminal is connected to the antenna side input / output terminal; and a reception connection mode in which the reception output terminal is connected to the antenna side input / output terminal. In the reception connection mode, one of the plurality of reception output terminals individually corresponding to the communication frequency band is selected and used for communication, and the antenna side input / output terminal is selected. And a switch circuit connected to the
The switch circuit handles a plurality of communication frequency bands including two communication frequency bands having an overlap between a terminal reception band of one communication frequency band and a terminal transmission band of the other communication frequency band. And a switch element that constitutes a switch circuit for switching between the switching mode and the reception connection mode is constituted by a high-frequency compound semiconductor transistor.
[0011]
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.
[0012]
Conventionally, a switch circuit using a PIN diode as a switching element has been used as an antenna switch of a multiband terminal. This switch circuit is inexpensive because the constituent elements of the peripheral bias circuit, including the PIN diode, can be mainly composed of coils and capacitors. However, good isolation characteristics can be obtained only in the vicinity of the set resonance frequency. In addition, leakage of the transmission signal to the reception output terminal side is relatively easy to occur. Therefore, when the terminal transmission band and the terminal reception band of two different communication frequency bands (bands) overlap, a band-pass filter circuit for extracting the terminal reception band of a narrow band specialized for the terminal reception band is provided. However, a transmission signal in a frequency band overlapping with the terminal transmission band passes through the transmission band, and flows into the receiving circuit side, thus easily causing a problem such as a malfunction.
[0013]
However, according to the present invention, a switch circuit for switching between two communication frequency bands having an overlap between one terminal reception band and the other terminal transmission band is used for switching between a transmission connection mode and a reception connection mode. The switch element was composed of a high-frequency compound semiconductor transistor. The high-frequency compound semiconductor transistor has extremely excellent isolation characteristics in a wide frequency band, and can reliably prevent a transmission signal from leaking to the reception output terminal side in the transmission connection mode. 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 passes through the terminal reception band extraction band-pass filter circuit and is received. A problem that flows into the circuit side and causes a malfunction or the like can be effectively prevented.
[0014]
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.
[0015]
Next, the high-frequency signal processing circuit of the present invention includes a demultiplexer circuit connected to the antenna-side input / output terminal and separating a reception signal received via the antenna into a high-frequency signal and a low-frequency signal. Can be configured as For example, as in a quad-band wireless telephone terminal, both the high-frequency signal and the low-frequency signal demultiplexed by the demultiplexing circuit are demultiplexed signals including a plurality of communication frequency bands, respectively. It is possible to adopt a configuration in which a switch circuit in which a switch element is formed of a high-frequency compound semiconductor transistor is provided on each output side of the split signal. With this configuration, in each switch circuit that handles the high-frequency signal and the low-frequency signal, it is possible to effectively prevent the transmission signal of the frequency band overlapping the terminal transmission band from leaking to the reception output terminal side. it can. In particular, in a switch circuit for a high-frequency signal in a higher frequency band, it is difficult to secure isolation characteristics with a conventional strip resonator type switch using a PIN diode. For this reason, it is necessary to add an extra element for improving the isolation, for example, by inserting a coil for forming a parallel resonator in parallel with the PIN diode, and there has been a problem that the circuit is enlarged. However, in the present invention, the use of the switch circuit constituted by the high-frequency compound semiconductor transistor eliminates the need for such an additional element, and the high-frequency signal processing circuit including the switch circuit, and thus the entire wireless telephone terminal, are compact. Can be configured.
[0016]
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 = it is _{{(f cH -f cL) -W} S} / (f cH -f cL) refers to 10% or less. This is because if J exceeds 10%, the accuracy of signal extraction in the terminal reception band is impaired. In particular, when the width of the terminal reception band is a narrow band of about 50 to 75 MHz, the bandpass filter circuit for extracting the terminal reception band should be a filter circuit including a surface acoustic wave resonator. It is desirable from the viewpoint of reducing the size and improving the extraction accuracy of signals in the terminal reception band.
[0017]
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.
[0018]
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.
[0019]
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.
[0020]
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.
[0021]
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. Switch circuits 42A and 42B are provided on the output sides of the respective demultiplexed signals, each of which includes a GaAs-based MESFET (or a monolithic element of a plurality of MESFETs) as a switch element. .
[0022]
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.
[0023]
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.
[0024]
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.
[0025]
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 mutually switches between a reception connection mode connected to the antenna side input / output terminal ANT. The switch circuit 42A is for processing lower frequency signals ▲ 2 ▼, reception circuit (reception unit 35A / 35B, demodulator 36A / 36B) of the cellular phone 1 receives the output and outputs the received signal to the terminal _{R X1} ( for _EGSM), R X2 (for GSM850), transmission circuit of a cellular phone 1 (modulation section 32A / 32B, the transmission unit 33A / 33B) transmit the input terminal _T X1 _T X2 (EGSM / GSM850 shared transmission signal is inputted from the (Described later)), and switches the connection between the reception output terminals R _X1 and R _X2 for the antenna-side input / output unit ANT and the transmission input terminals T _X1 T _X2 . The switch circuit 42B is for processing the high frequency side signal {circle around (4)}, and is a reception output terminal for outputting a reception signal to the reception circuit (reception unit 35C / 35D, demodulation unit 36C / 36D) side of the mobile phone 1. R _X3 (for PCS), R _X4 (for DCS) and transmission input terminals T _X3 T _X4 (to which transmission signals from the transmission circuits (modulation units 32C / 32D, transmission units 33C / 33D) of the mobile phone 1 are input. and a PCS / DCS sharing (described later)) which switches the connection of the reception output terminal for the antenna side input-output unit ANT _{R X3, R X4} and the transmission input terminal _T X3 _{T X4.} Note that C4 to C8 in FIG. 3 are DC blocking capacitors.
[0026]
The low-frequency side switch circuit 42A has a drain and a source connected on each path connecting the antenna-side input / output unit ANT and the reception output terminal R _X1 , the reception output terminal R _X2, and the transmission input terminal T _X1 T _X2 . Transistors Tr1, Tr2, Tr3 (in this embodiment, CXG1101TN manufactured by SONY Corporation) are provided, each of which is composed of a GaAs-based MESFET. , VC2, and VC3 are individually input. VC1, VC2, and VC3 are binary control signals, and in the transmission connection mode, only the transistor Tr3 corresponding to the transmission input terminal T _X1 T _X2 is turned ON, and the other VC1, VC2, and VC3 are turned OFF. Is controlled. In the transmission connection mode, the transistor Tr1 or the transistor Tr2 corresponding to one of the reception output terminal R _X1 and the reception output terminal R _X2 is selectively turned on, and the other transistors are turned off so that VC1, VC2 and VC3 are turned off. The input state is controlled.
[0027]
The high-frequency side switch circuit 42B has a drain and a source connected on each path connecting the antenna-side input / output unit ANT to the reception output terminal R _X3 , the reception output terminal R _X4, and the transmission input terminal T _X3 T _X4. Tr4, Tr5 and Tr6 (in this embodiment, CXG1101TN manufactured by Sony Corporation) are provided, each of which is made of a GaAs-based MESFET. The gates of these transistors Tr4, Tr5 and Tr6 are used for switch control. Signals VC4, VC5, and VC6 are individually input. VC4, VC5, VC6 are control signals of any binary, the transmission connection mode, only the transistor Tr6 is turned ON corresponding to the transmission input terminal _T X3 _{T X4,} so that other becomes OFF VC4, VC5, VC6 Is controlled. In the transmission connection mode, the transistor Tr4 or the transistor Tr5 corresponding to one of the reception output terminal R _X3 and the reception output terminal R _X4 is selectively turned on, and the other transistors are turned off so that VC4, VC5 and VC6 are turned off. The input state is controlled.
[0028]
Since only one of the four communication frequency bands shared by the switch circuits 42A and 42B is selected for transmission and reception, the switch circuits not involved in transmission and reception are switched so that all transistors are turned off. The input state of the control signal is controlled.
[0029]
The terminal reception band extraction bandpass filter circuits 40A (for EGSM: passband 880 to 960 MHz), 40B (for GSM850: passband 824 to 894 MHz), 40C (for PCS: passband 1850 to 1990 MHz) and 40D in FIG. (For DCS: pass band 1710 to 1880 MHz) are connected to the reception output terminals R _X1 , R _X2 , R _X3 , and R _X4 , and in this embodiment, all are narrow band filters including a surface acoustic wave resonator. It is configured as a circuit. 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.
[0030]
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 _X1 T _X2 and T _X3 T _X4 (42A, 42B) provided on both output sides of the low-frequency side signal (2) are connected to two communication frequencies handled by the switch circuits 42A, 42B. It is configured as a single terminal shared in the band. As shown in FIG. 1, the input of the transmission signal to each of the transmission input terminals T _X1 T _X2 and T _X3 T _X4 is performed via the high-frequency low-noise amplifiers 21 and 22.
[0031]
Next, as shown in FIG. 3, the transmission input terminals T _X1 T _X2 and T _X3 T _X4 are respectively provided with transmission low-pass filter circuits 41A and 41B having a pass band including a terminal transmission band of two communication frequencies. It is connected. 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, even if the band-pass filters 40A to 40D of narrow bands are not separately provided as in the receiving terminals R _{X1 to} R _X4 in FIG. Can be sufficiently removed. Further, since the pass band of the LC low-pass filter circuit is relatively wide, as shown 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 LC 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.
[0032]
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 capacitors C101 to C103 / C201 to C203 and coils L101 / L201, respectively. In particular, for the switch circuit 42B handling the high-frequency side signal {circle around (4)}, the adoption of the transmission low-pass filter circuit 41B makes it possible to inexpensively replace an expensive narrow-band filter circuit including a surface acoustic wave resonator. In addition to the above, the coil L201 used for the higher frequency can be downsized, and there is an advantage that the entire circuit can be made compact.
[0033]
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 can be significantly reduced.
[0034]
For example, although not shown in FIG. 3, when the resistor 55 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.
[0035]
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 the capacitor 54, which is a component 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 occurrence of dead space is eliminated and the stacked body 80 is made compact. Can be.
[0036]
According to the high-frequency signal processing circuit 2 and the quad-band mobile phone 1 (FIG. 1) using the same, in the transmission connection mode, the switch circuits 42A and 42B using the GaAs MESFET shown in FIG. The path leading to the transmission circuit is reliably cut off by the transistors Tr1, Tr2, Tr4, Tr5 in the OFF state, and the isolation characteristic of the transmission signal to the receiving circuit side is dramatically improved. As a result, as already described with reference to FIG. 9 and FIG. 10, even though the terminal transmission band and the terminal reception band of two different communication frequency bands (EGSM / GSM850 and PCS / DCS) overlap, the transmission is performed. The problem that a part of the signal leaks to the receiving circuit side hardly occurs.
[0037]
Note that the above-described embodiment has been described as an example of application to a quad-band mobile phone. However, such as a triple-band mobile phone, there is an overlap between one terminal reception band and the other terminal transmission band. The present invention can be applied to any mobile phone of a type that handles one communication frequency band (or a plurality of communication frequency bands more than that) with one switch circuit. Although the MESFET is used as the high-frequency compound semiconductor transistor used for switching between the transmission connection mode and the reception connection mode in the above embodiment, the transistor may naturally be constituted by a HEMT or an HBT. The switch circuit may be configured as a high-frequency IC integrated on a semiconductor substrate (for example, a GaAs substrate) with other devices.
[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.
FIG. 9 is a first explanatory diagram of a switch circuit that handles two communication frequency bands having an overlap between one terminal reception band and the other terminal transmission band.
FIG. 10 is also a second explanatory diagram.
[Explanation of symbols]
1. Digital mobile phones (wireless telephone terminals)
2 High frequency signal processing circuits 32A to 32D Modulation section (transmission circuit)
33A to 33D transmission unit (transmission circuit)
35A to 35D receiving unit (receiving circuit)
36A to 36D demodulation unit (receiving circuit)
39 Antennas 40A, 40B, 40C, 40D Terminal reception band extraction band-pass filter circuits 41A, 41B Transmission low-pass filters 42A, 42B Switch circuits Tr1 to Tr6, 51 GaAs-based MESFET (high-frequency compound semiconductor transistor)
44 Demultiplexing circuit 45 Low-pass filter circuit 46 High-pass filter circuits 53, 54, 55 Circuit pattern 80 Laminated bodies R _{X1 to} R _X4 Reception output terminals T _X1 T _X2 , T _X3 T _X4 Transmission input terminals ANT Antenna-side input / output terminals

Claims (6)

There is a high-frequency signal processing circuit used in 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 transmission input terminal to which a transmission signal from an individual transmission circuit provided for each communication frequency band is input in the wireless telephone terminal, and a reception signal from the antenna, and the communication frequency band in the wireless telephone terminal. A plurality of reception output terminals provided for each of the individual reception circuits provided for each transmission terminal, wherein the transmission input terminal is connected to the antenna-side input / output terminal, a transmission connection mode, and the reception output terminal is connected to the antenna. The reception connection mode connected to the side input / output terminal and, in the reception connection mode, one of a plurality of reception output terminals individually corresponding to the communication frequency band used for communication. And a switch circuit for selecting one and connecting to the antenna-side input / output terminal.
The switch circuit handles a plurality of communication frequency bands including two communication frequency bands having an overlap between a terminal reception band of one communication frequency band and a terminal transmission band of the other communication frequency band. A high-frequency signal processing circuit, wherein a switch element forming a switch circuit for switching between a connection mode and the reception connection mode is formed of a high-frequency compound semiconductor transistor. 2. The high-frequency signal processing circuit according to claim 1, wherein said high-frequency compound semiconductor transistor comprises a GaAs-based field-effect transistor. A demultiplexing circuit that is connected to the antenna-side input / output terminal and that separates a reception signal received via the antenna into a high-frequency signal and a low-frequency signal; Both the high-frequency signal and the low-frequency signal are demultiplexed signals including the plurality of communication frequency bands, respectively, and the output side of each demultiplexed signal includes the switch element in the high-frequency compound semiconductor transistor. The high-frequency signal processing circuit according to claim 1, wherein the configured switch circuit is provided. 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 signal processing circuit according to claim 3, wherein the high-frequency compound semiconductor transistor constituting the switch circuit is mounted on a surface of the stacked body. A transmission input terminal of at least one of the switch circuits provided on the output side of the high-frequency side signal of the demultiplexing circuit is configured as a single terminal shared in the two communication frequency bands, and 5. The high-frequency signal processing circuit according to claim 4, wherein a transmission low-pass filter circuit having a pass band including a terminal transmission band of the two communication frequencies is connected to the input terminal. A high-frequency signal processing circuit according to any one of claims 1 to 5,
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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