JP2008166893A - Transmission/reception circuit of wireless terminal equipment by dual mode communication - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the number of components and to suppress the generation of spuriousness. <P>SOLUTION: In the transmission/reception circuit 10, an antenna 11 is connected through a BPF 12 to a circulator 13, and the BPF 12 makes signals by the frequency of the using frequency band of the wireless terminal equipment pass through and eliminates disturbance waves out of the using frequency band. For the circulator 13, a circuit connected through the BPF 12 to the antenna 11, an input circuit to a low noise amplifier 14 and an output circuit from a power amplifier 15 are successively connected in the order and in the direction to three terminals, functions of both of a changeover switch and an isolator are provided, and the function of a band pass filter for making only the signals by the using frequency pass through is provided together further. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a transmitter / receiver circuit of a radio terminal by dual mode communication that can reduce spurious generated when signals are simultaneously transmitted by two adjacent transmitter / receiver circuits while improving reception characteristics for spurious signals at the time of reception. It is.

  As a conventional transmission / reception circuit of a wireless terminal using dual mode communication, for example, there is a communication device disclosed in Japanese Patent Laid-Open No. 2005-73078 (Patent Document 1). For example, as shown in FIG. 2, the main part of the transmission / reception circuit including the antenna of the communication apparatus disclosed in Patent Document 1 includes two transmission / reception circuits 110 and 120, and antennas 111 and 121, switches 112 and 122, and a low-noise amplifier 113. , 123, reception band pass filters (BPF) 114, 124, transmission BPFs 115, 125, and power amplifiers 116, 126.

  In the transmission / reception circuit 110, the antenna 111 is connected to the switch 112, receives a signal having a reception frequency included in one frequency band, and transmits a signal having the transmission frequency. The switch 112 connects the antenna 111 to the low noise amplifier 113 for reception and to the power amplifier 116 for transmission. The low noise amplifier 113 passes only the signal having the reception frequency through the reception BPF 114 and sends it to the demodulation circuit. The transmission BPF 115 passes only the signal of the transmission frequency out of the output of the modulation circuit and sends it to the power amplifier 116. Since the transmission / reception circuit 120 has the same circuit configuration, the description thereof is omitted.

  As described above, in Patent Document 1, in order to reduce the occurrence of spurious in each of the transmission circuit and the reception circuit, a BPF that passes a signal in each use frequency band of transmission and reception that removes a signal due to an extra frequency is used.

  On the other hand, for example, there is a wireless device disclosed in Japanese Patent Laid-Open No. 2006-262314 (Patent Document 2). The main part of the transmission / reception circuit including the antenna of the wireless device of Patent Document 2 is, for example, as shown in FIG. 3, one transmission / reception circuit 210 including an antenna 211, a common BPF 212, a switch 213, a low noise amplifier 214, and a power amplifier 215. , And an isolator 216. The other transmission / reception circuit 220 includes an antenna 221, a switch 222, a low noise amplifier 223, a reception BPF 224, a transmission BPF 225, a power amplifier 226, and an isolator 216.

  The configuration of Patent Document 2 is the same as that of Patent Document 1, but one difference is that the reception BPF 114 and the transmission BPF 115 in the transmission / reception circuit 110 in FIG. 2 are not in the transmission / reception circuit 210 in FIG. Instead, one common BPF 212 is provided between the antenna 211 and the switch 213.

  For example, a dual mode of a 1.9 GHz band radio using a transmission frequency of 1850 to 1910 MHz and a reception frequency of 1930 to 1990 MHz and a 2 GHz band radio using a transmission frequency of 1920 to 1980 MHz and a reception frequency of 2110 to 2170 MHz. This is realized in the case of. That is, it is possible to reduce the number of BPFs by putting together the transmission / reception circuits with the reception frequencies 1930 to 1990 MHz of the 1.9 GHz band radio and the transmission frequencies 1920 to 1980 MHz of the 2 GHz band radio in one transmission / reception circuit 210. When compared with the transmission / reception circuit 110, the apparatus can be reduced in size and weight.

  Further, the second difference is that the isolators 216 and 227 are respectively provided between the switches 213 and 222 and the power amplifiers 215 and 226 on the transmission circuit side. It is described that this isolator is provided to prevent destruction of the low noise amplifiers 214 and 223 and the receiving BPF 224 on the receiving circuit side due to the transmission power of the power amplifiers 215 and 226.

Japanese Patent Laying-Open No. 2005-73078 (FIG. 1) JP 2006-262314 A (FIG. 2)

  A wireless device having the above-described two transmission / reception circuits in the same housing is a wireless system having different frequency bands. However, a dual-mode wireless terminal has a narrow communication range of one base station such as PHS (Personal Handyphone System), and the frequency band per terminal is wider than that of a mobile phone. Some access two base stations at different frequencies.

  When two adjacent transmitting / receiving circuits transmit at the same time, spurious (intermodulation distortion) is a problem. For example, as shown in FIG. 3, when two adjacent transmission / reception circuits 210 and 220 simultaneously transmit signals at different frequencies F1 and F2 that are adjacent to each other, the transmission / reception circuit 210 receives a radio wave having a transmission frequency F2 of the transmission / reception circuit 220. Is transmitted to the transmission circuit of the transmission / reception circuit 210 through the antenna 211. Therefore, spurious is generated at the frequency “F1-Fd” and the frequency “F1-2Fd” due to the distortion characteristics of the power amplifier 215 having a nonlinear element. Similarly, in the transmission / reception circuit 220, the radio wave having the transmission frequency F1 of the transmission / reception circuit 210 is transmitted to the transmission circuit of the transmission / reception circuit 220 through the antenna 221, so that the frequency “F2 + Fd” and the frequency characteristics “F2 + Fd” and Spurious is generated at the frequency “F2 + 2Fd”.

  In the circuit of FIG. 3, in the two transmission / reception circuits 210 and 220, the radio waves of the two transmission / reception circuits 210 and 220 wrap around each other's transmission circuit by the isolators 216 and 227 inserted on the output sides of the power amplifiers 215 and 226, respectively. The amount, that is, the signal level in the reverse direction is reduced, and the occurrence of spurious is suppressed. However, in this circuit configuration, there is a problem that an isolator is necessary and transmission loss occurs due to this.

  Further, in order to attenuate unnecessary frequencies with respect to the receiving circuit, BPFs 212 and 224 that pass only a signal having a frequency to be used, or a low noise amplifier 223 that has an effect of suppressing unnecessary waves, are used. Improvements are being made. However, in order to further improve the spurious reception characteristics, it is necessary to cope with the addition of a filter.

  The problem to be solved is that it is impossible to reduce the number of parts and simultaneously suppress the occurrence of spurious.

  The main feature of the present invention is that a circulator is used for switching between a transmission circuit and a reception circuit in order to reduce the number of components and suppress spurious generation.

  That is, the transmission / reception circuit of the wireless terminal according to the present invention includes two antennas that the wireless terminal includes for dual mode communication, and includes an antenna, a transmission circuit, and a reception circuit. A circulator is used to switch the connections.

  The circulator is connected to each of an antenna, a transmission circuit, and a reception circuit, passes a signal having a transmission frequency in a transmission / reception frequency band to be used from the transmission circuit to the antenna, and a signal having a reception frequency from the antenna is the reception circuit. The connection between the antenna and the transmission circuit and the reception circuit is switched.

  The transmission circuit includes a power amplifier that directly inputs a signal based on a transmission frequency from a modulation circuit and directly outputs the signal to the circulator, and the reception circuit directly inputs a signal based on the reception frequency from the circulator. A low-noise amplifier that directly outputs to the demodulation circuit.

  In addition, in the transmission / reception circuit of the wireless terminal, having a bandpass filter that passes a signal in a transmission / reception frequency band used between the antenna and the circulator eliminates an extra frequency that causes spurious. preferable.

  Since the circulator is used for switching the connection between the antenna, the transmission circuit, and the reception circuit in each of the transmission / reception circuits of the wireless terminal using dual mode communication according to the present invention, a signal based on the transmission frequency from the transmission circuit flows to the antenna, The signal by the reception frequency flows to the reception circuit, and the separation is more reliable than the changeover switch due to the direction of transmission. Therefore, it is possible to suppress a signal having a transmission frequency received from an adjacent transceiver from the own antenna from entering the own transmission circuit. As a result, it is possible to avoid the occurrence of spurious in the transmission circuit. Further, since the interference wave to the receiving circuit is attenuated by the bandpass filter characteristic of the circulator and its insertion loss, the improvement of the spurious reception characteristic can be expected. Thus, since the circulator has the function of an isolator, the functions of both the changeover switch and the isolator can be covered by one, contributing to a reduction in the number of parts.

  The purpose of reducing the number of parts and suppressing spurious generation was realized by using a circulator for switching the connection between the antenna, the transmission circuit, and the reception circuit in each of two adjacent transmission / reception circuits.

  This embodiment will be described with reference to the drawings. FIG. 1 is a circuit diagram showing in block form an embodiment of a transmission / reception circuit in a wireless terminal using dual mode communication according to the present invention.

  The radio terminal using dual mode communication has two transmission / reception circuits 10 and 20 as shown in the figure. In the transmission / reception circuit 10, an antenna 11, a BPF 12 for transmission / reception, a circulator 13, a low noise amplifier 14, and a power amplifier 15 are illustrated. Similarly, the transmission / reception circuit 20 includes an antenna 21, a BPF 22 for transmission / reception, a circulator 23, a low noise amplifier 24, and a power amplifier 25.

  In the transmission / reception circuit 10, the antenna 11 is connected to the circulator 13 via the BPF 12. The BPF 12 passes a signal having a frequency in a frequency band used by the wireless terminal, and eliminates an interference wave outside the used frequency band. The circulator 13 is a change-over switch that sequentially connects, in this order and in this direction, a circuit connected to the antenna 11 via the BPF 12, an input circuit to the low-noise amplifier 14, and an output circuit from the power amplifier 15 to three terminals. Demonstrate the effect of. This is because the transmission loss is small in one direction and large in the reverse direction as a characteristic of the circulator.

  Therefore, due to the switching action of the circulator 13, in the connection from the circuit to the antenna 11 to the low noise amplifier 14, a signal based on the reception frequency from the antenna 11 is sent only to the low noise amplifier 14 and sent to the power amplifier 15. I can't. In the connection from the low noise amplifier 14 to the power amplifier 15, there is no frequency transmission to the power amplifier 15 because there is no signal transmission at a high frequency to the circulator 13. In the connection from the power amplifier 15 to the circuit of the antenna 11, a signal based on the output frequency of the power amplifier 15 is sent only to the antenna 11 and is not sent to the low noise amplifier 14. Since the illustrated transmission / reception circuit 20 has the same circuit configuration, the description thereof is omitted.

  Therefore, when the adjacent transmission / reception circuits 10 and 20 simultaneously transmit signals of the frequencies F1 and F2 from the antennas 11 and 21, the signal of the frequency F2 radiated from the antenna 21 is transferred from the antenna 11 to the inside of the transmission / reception circuit 10. Is transmitted. The signal of the frequency F2 is transmitted to the low noise amplifier 14 by the circulator 13, and is greatly attenuated in the direction toward the power amplifier 15, thereby suppressing the wraparound of the signal by the frequency F2. That is, the circulator 13 can suppress the occurrence of spurious in the transmission circuit. Similarly, signal wraparound due to the reverse transmission frequency F1 can be suppressed.

  Further, since the circulator can be manufactured so as to pass only the used frequency band, the circulator also serves as a bandpass filter that attenuates signals by the upper and lower frequencies to remove unnecessary waves. Therefore, even in the reception circuit, the attenuation effect of the interference wave is increased, and an improvement in spurious reception characteristics can be expected. Thus, since the circulator also has a function of a bandpass filter in addition to a function of a changeover switch and a function of an isolator, the number of parts can be reduced from the conventional circuit described above.

  Furthermore, in this embodiment, a bandpass filter that allows only the used frequency band to pass is inserted between the antenna and the circulator for thorough deletion of the interference wave.

  Since such a configuration is adopted, it is possible to realize two transmission / reception circuits for the dual mode that are effective in reducing the number of parts and at the same time suppressing the occurrence of spurious.

  By using a circulator to switch the connection between the antenna, transmitter circuit and receiver circuit in each of the two adjacent transmitter / receiver circuits, it is easy to reduce the number of parts and at the same time suppress the occurrence of spurious, improving economic and quality. It can be applied to wireless terminals that require

1 is a circuit diagram illustrating a block diagram of an embodiment of a transceiver circuit of a wireless terminal using dual mode communication according to the present invention. FIG. FIG. 6 is a circuit diagram illustrating an example of a transmission / reception circuit of a wireless terminal using conventional dual mode communication. FIG. 6 is a circuit diagram illustrating an example of a transmission / reception circuit of a wireless terminal using conventional dual mode communication. It is explanatory drawing which shows an example of generation | occurrence | production of the spurious by two frequencies with a graph.

Explanation of symbols

10, 20 Transmission / reception circuit 11, 21 Antenna 12, 22 BPF
13, 23 Circulator 14, 24 Low noise amplifier 15, 25 Power amplifier

Claims (6)

In each of the two radio terminals equipped for dual mode communication, in the transmission / reception circuit having an antenna, a transmission circuit and a reception circuit,
Connect to each of the antenna, the transmission circuit and the reception circuit, and pass a signal with a transmission frequency in a transmission / reception frequency band to be used from the transmission circuit to the antenna, and pass a signal with a reception frequency from the antenna to the reception circuit. A circulator for switching the connection between the antenna and the transmission circuit and the reception circuit,
A power amplifier that is provided in the transmission circuit and that directly inputs a signal at a transmission frequency from a modulation circuit and directly outputs the signal to the circulator;
A low-noise amplifier that is provided in the receiving circuit and that directly inputs a signal based on a reception frequency from the circulator and directly outputs the signal to a demodulation circuit;
A transmission / reception circuit for a wireless terminal, comprising:   2. The transmission / reception circuit of a wireless terminal according to claim 1, further comprising a band-pass filter that allows a signal in a required transmission / reception frequency band to pass between the antenna and the circulator. .   In each of the two transmission / reception circuits that the wireless terminal has for dual mode communication, it is connected to each of the antenna, the transmission circuit, and the reception circuit, and a signal having a transmission frequency in a required transmission / reception frequency band is passed from the transmission circuit to the antenna. And a circulator for switching a connection between the antenna, the transmission circuit, and the reception circuit by allowing a signal having a reception frequency from the antenna to pass through the reception circuit.   4. The transmission / reception circuit of the wireless terminal according to claim 3, wherein the transmission circuit includes a power amplifier that inputs a signal having a transmission frequency from a modulation circuit and directly outputs the signal to the circulator. Transmission / reception circuit.   4. The wireless terminal transmission / reception circuit according to claim 3, wherein the reception circuit includes a low noise amplifier that directly inputs a signal having a reception frequency from the circulator and outputs the signal to a demodulation circuit. Transmission / reception circuit.   6. The transmission / reception circuit of the wireless terminal according to claim 3, further comprising a band-pass filter that passes a signal in a transmission / reception frequency band used between the antenna and the circulator. Transmitter / receiver circuit for wireless terminal.

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