JP2007336115A - Transmitter receiver having incorporated antenna switch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make compact in size transmitter receiver used for a wireless communication system which performs transmission and reception on a time-division basis like a wireless LAN by eliminating the need for an attenuator between a transmission/reception switch and a receiving circuit. <P>SOLUTION: When the intensity of a reception signal is larger than a certain level, the wireless communication system which performs transmission and reception on a time-division basis like a wireless LAN switches the transmission/reception switch (12) to the side of a power amplifier (13) for transmission even during reception to attenuate the reception signal by the transmission/reception switch and then input the signal to a receiving circuit. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a transmitter / receiver used in a transmission / reception time division wireless communication system including a so-called antenna switch that switches an antenna connection between a transmission side and a reception side, and more particularly, wireless communication that performs wireless communication in a relatively narrow area. The present invention relates to a technology that is effective when used for a transceiver used in a LAN (local area network).

  A transceiver used in a transmission / reception time-division wireless communication system that performs transmission and reception in a time division manner, such as a wireless LAN, is provided with a transmission / reception changeover switch called an antenna switch that switches an antenna connection between a transmission side and a reception side. At the time of reception, this switch is switched to the reception side so that the reception signal is input to a reception circuit (RF-IC) having a high gain amplifier.

  By the way, in wireless communication, if the reception intensity is too high, the amplifier is saturated and the received signal is distorted and the data error rate is increased. Therefore, in order to reduce the distortion of the received signal, an attenuator is placed after the transmission / reception selector switch. It is preferable to attenuate the received signal and input the signal to the receiving circuit (RF-IC).

  However, when an attenuator is provided, it becomes difficult to demodulate a weak received signal with low strength. Therefore, there is a technique that detects the intensity of the received signal and provides a switch for switching the signal path so that the attenuator is passed when the received intensity is high and the attenuator is not passed when the received intensity is low.

In addition, the wireless LAN is provided with a so-called diversity antenna having a plurality of antennas and an antenna changeover switch, and a switch switching control is performed so as to select a received signal from an antenna having a higher reception strength. Even in a wireless LAN having a diversity antenna, an attenuator is provided after the transmission / reception selector switch so that the signal path is switched so that the attenuator is passed when the reception strength is high and the attenuator is not passed when the reception strength is low. There is a technology.
JP 2002-223176 A JP 07-2977752 A Japanese Patent Laid-Open No. 06-252794 Japanese Patent Laid-Open No. 06-140959 Japanese Patent Laid-Open No. 11-068613 JP 2005-348137 A JP 2005-203947 A

  In a wireless LAN in which an attenuator is provided after the transmission / reception changeover switch, an attenuator and a signal path changeover switch for passing or bypassing the attenuator are necessary. There is a problem that it cannot be realized. In recent years, a receiving circuit for amplifying or downconverting a received signal has been provided as an integrated circuit on one semiconductor chip together with a transmitting circuit for upconverting a transmitted signal. Since it is common to configure an external circuit by combining components such as a resistor and a capacitor, it becomes an obstacle to downsizing of the device.

  In mobile phones such as PDC (Personal Digital Cellular) and PHS (Personal Handy-phone System) systems, the received signal level is detected, and if the threshold is exceeded, the demodulator moves the RF switch to the transmitting unit side that does not transmit output. There has been proposed an invention in which switching is performed and a large attenuation is applied to the input of the receiving unit so that the automatic gain control function of the amplifying unit can be realized with a simple circuit configuration (Patent Document 1).

  Also, in a TDD (Time Division Duplex) wireless communication device, even when receiving, a transmission / reception switch that switches the antenna and the transmission circuit to a connected state at the time of transmission and switches the antenna and the receiving circuit to a connected state at the time of reception. An invention configured to cause the transmission / reception switch to function as a high-frequency attenuator between the antenna and the receiving circuit by switching the antenna and the receiving circuit to a disconnected state if the strength of the antenna reception signal is equal to or greater than a predetermined value. It has been proposed (Patent Document 2).

  The inventions related to the above-mentioned prior application are mainly related to wireless communication devices for telephone calls, and are different from the wireless LAN according to the present invention used exclusively for data communication. The wireless LAN is CSMA (Carrier Sense Multiple Access) with variable transmission time and reception time, whereas TDMA (Time Division Multiple Access) has a fixed transmission time and reception time. In addition, the inventions according to the prior applications all relate to controlling the gain (amplification factor) of the transmission circuit only by switching the transmission / reception selector switch to the transmission side when the strength of the received signal is high. Not disclosed.

  An object of the present invention is to reduce the size and weight of an apparatus by eliminating the need for an attenuator between a transmission / reception switch and a receiving circuit in a transceiver used in a wireless communication system that performs transmission and reception in a time division manner, such as a wireless LAN. And to reduce the cost.

  The present invention includes an antenna, a transmission circuit, a reception circuit, a transmission / reception switching means, and a control circuit, and is a transceiver used in a radio communication system that performs transmission and reception in a time division manner. When the signal level is equal to or higher than a predetermined level, the transmission / reception switching unit is switched to the transmission circuit side even during reception, and the reception signal is attenuated by the transmission / reception switching unit and input to the reception circuit. Also used in a wireless communication system comprising a plurality of antennas, an antenna switching means for selecting one of the plurality of antennas, a transmission circuit, a reception circuit, a transmission / reception switching means, and a control circuit, and performing transmission and reception in a time division manner In the transmitter / receiver, the control circuit switches the transmission / reception switching means to the transmission circuit side even during reception when the intensity of the reception signal is equal to or higher than a preset first level, and the transmission / reception switching of the reception signal is performed. The signal is attenuated by the means and input to the receiving circuit. As a result, an attenuator and a signal path switching circuit are not required, and the number of parts of the apparatus can be reduced and the size can be reduced.

  Here, preferably, when the intensity of the received signal is equal to or higher than the predetermined level, the control circuit lowers the level of the transmission signal by reducing the gain of the amplifier in the transmission circuit during transmission. As a result, when processing the received signal on the server or repeater side that receives the signal, the distortion of the signal can be reduced to reduce the data error rate, and the power consumption of the terminal can be reduced by reducing the transmission level. Can be reduced.

  Further preferably, the control circuit controls the antenna switching means at the time of transmission when the intensity of the received signal is lower than the first level and higher than a second level lower than the first level. The reception signal from the antenna with the lower level is input to the reception circuit. Thereby, the level of the received signal input to the receiving circuit can be controlled in multiple stages according to the received signal strength.

  According to the present invention, in a transceiver used in a wireless communication system that performs transmission and reception in a time division manner, such as a wireless LAN, an attenuator between the transmission / reception switch and the reception circuit is not required, and the apparatus is reduced in size and weight. In addition, the cost can be reduced.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an embodiment of a transceiver for a wireless LAN suitable for application of the present invention.
The transceiver according to the present embodiment includes an antenna 11 that transmits and receives signal radio waves, a switch 12 for transmission and reception switching, a power amplifier 13 that amplifies a transmission signal and transmits the signal from the antenna 11, and down-converts the reception signal. Transmission / reception unit 20 for up-converting transmission signals, and baseband unit 30 for modulation / demodulation and baseband processing.

  The transmission / reception unit 20 includes an amplifier 21 that amplifies the reception signal, a mixer 22 that mixes the reception signal amplified by the amplifier 21 and an oscillation signal (high frequency signal) of a predetermined frequency, and down-converts the signal to a low frequency signal. Prepare. The transmission / reception unit 20 includes a mixer 27 that up-converts the modulated transmission signal and outputs the converted transmission signal to the transmission power amplifier 13.

  The baseband unit 30 includes a demodulation circuit 32 that demodulates the reception signal output from the transmission / reception unit 20 to restore reception data, a modulation circuit 33 that modulates transmission data, and a signal level measurement circuit that measures the amplitude level of the reception signal. 35. Generates a control signal for a circuit in the chip and a switching signal for the transmission / reception selector switch 12, and generates gain control data for controlling the gain of the amplifier in the transmission / reception unit 20 based on the output of the signal level measurement circuit 35. And a system control circuit 36 for sending the data to the transmitting / receiving unit 20.

  The system control circuit 36 can be configured by a circuit having the same configuration as a general-purpose microcomputer or microprocessor (hereinafter referred to as a microcomputer) that operates according to a program. The wireless LAN system according to the IEEE802.11a standard uses an OFDM (Orthogonal Frequency Division Multiplexing) system as a modulation system. When this embodiment is applied to a wireless LAN system, the demodulation circuit 32 and the modulation circuit 33 are used. The baseband unit 30 is configured to perform modulation / demodulation according to the OFDM scheme.

  In the transceiver of the present embodiment, when the received signal intensity measured by the signal level measuring circuit 35 is equal to or higher than a certain level, the system control circuit (microcomputer) 36 sets the transmission / reception changeover switch 12 even during reception. A control signal S1 that switches to the transmission power amplifier side is generated and output. The transmission / reception change-over switch 12 has such a characteristic that the received signal is attenuated by about 15 to 20 dB and transmitted to the amplifier 21 when switched to the power amplifier side.

  Furthermore, in this embodiment, when the intensity of the received signal measured by the signal level measurement circuit 35 is equal to or higher than a certain level, the system control circuit (microcomputer) 36 reduces the gain of the power amplifier 13 to the lower side during transmission. The switching control signal S2 is configured to be output to the power amplifier 13.

  In many cases, a wireless LAN is expected to be used without moving the terminal, that is, in a state in which the distance from the server or the repeater does not change. Therefore, the strength of the received signal is high. In such a case, communication is possible even if the transmission signal level is lowered, and at the server or repeater side that receives the signal by lowering the transmission level. It is possible to reduce the signal error rate and reduce the data error rate when processing the received signal. Moreover, there is an advantage that the power consumption of the terminal can be reduced by lowering the transmission level.

FIG. 2 shows an example of a specific procedure for switching control processing of the transmission / reception selector switch 12 executed by the system control circuit 36.
When this switching control process is started, the reception level is first measured by the signal level measurement circuit 35 (step S1). Next, it is determined whether or not the measured reception level is higher than a predetermined level such as -10 dB (step S2). When it is determined that the reception level is higher than −10 dB, the process proceeds to step S3, and a control signal S1 that switches the transmission / reception selector switch 12 to the transmission side is generated and output (step S3). At the same time, a predetermined flag ANT Flag is set to “1” to store that the transmission / reception selector switch 12 is on the transmission side, and the process returns to step S1 (step S4).

  If it is determined in step S2 that the reception level is lower than -10 dB, the process proceeds to step S5, where the reception level is lower than a predetermined level such as -35 dB and the flag ANT Flag is "1". Judge whether or not. If it is determined that “Yes”, that is, the reception level is lower than −10 dB and the flag ANT Flag is “1”, the control signal S1 that switches the transmission / reception selector switch 12 to the reception side is generated and output. (Step S6).

  At the same time, the flag ANT Flag is cleared to “0” to store that the transmission / reception selector switch 12 is on the receiving side, and the process returns to step S1 (step S7). If it is determined in step S5 that the reception level is higher than −35 dB or the flag ANT Flag is “0”, the process returns to step S1 without switching the transmission / reception selector switch 12 and the reception level is measured.

  In the processing flow of FIG. 2, since the determination is performed at different levels in steps S1 and S5, hysteresis can be provided, and the transmission / reception changeover switch 12 is switched between the transmission side and the reception side due to slight fluctuation of the reception signal. It is possible to prevent frequent switching.

  Although not shown in FIG. 2, the system control circuit 36 switches to the transmission side when the transmission / reception selector switch 12 is on the reception side with reference to the flag ANT Flag at the start of transmission processing. On the other hand, when the transmission / reception selector switch 12 is on the transmission side, the control signal S2 is generated so that the gain of the power amplifier 13 is switched to the lower side without switching. It is designed to output.

FIG. 3 shows another embodiment of a transceiver for a wireless LAN suitable for application of the present invention.
The transceiver of the present embodiment includes a diversity antenna provided with a plurality of antennas for transmitting and receiving signal radio waves. In this embodiment, an antenna changeover switch 14 for selecting which antenna to use is provided between the antennas 11 a and 11 b in addition to the transmission / reception changeover switch 12. The antenna selector switch 14 is switched by a control signal S3 from the system control circuit 36.

  Also in this embodiment, as in the first embodiment, a measurement circuit 35 for measuring the level of the received signal is provided. When the received signal strength is higher than a certain level, it is during reception. In addition, by switching the transmission / reception changeover switch 12 to the transmission side, the attenuation of the switch (-15 to 20 dB) is used to lower the level of the received signal and input it to the receiving circuit so that the signal distortion can be reduced. It has become. Further, when the transmission / reception selector switch 12 is switched to the transmission side at the time of reception, the gain of the power amplifier 13 is lowered at the time of transmission to lower the level of the transmission signal.

  FIG. 4 shows an example of a specific procedure of the switching control processing of the transmission / reception selector switch 12 and the antenna selector switch 14 executed by the system control circuit 36 in the second embodiment.

  When this switching control process is started, first, the reception level is measured by the signal level measurement circuit 35 (step S11). Next, it is determined whether or not the measured reception level is higher than a predetermined level such as -10 dB (step S12). If it is determined that the reception level is higher than −10 dB, the process proceeds to step S13 to determine which antenna is connected. Here, when the connected antenna is the antenna 1 (11a), the antenna changeover switch 14 is moved to the antenna 2 (11b) side, and when the connected antenna is the antenna 2, the antenna changeover switch 14 is turned off. A control signal S3 for switching to the antenna 1 side is generated and output (steps S14 and S17).

  Subsequently, the level of the received signal from the antenna on the switched side is measured by the measurement circuit 35 (steps S15 and S18). Then, it is determined whether or not the measured reception level is higher than the -10 dB level again (steps S16 and S19). Here, if it is determined that the reception level is again higher than the −10 dB level, the transmission / reception selector switch 12 is switched to the transmission side (step S20). At the same time, a predetermined flag ANT Flag is set to “1” to store that the transmission / reception selector switch 12 is on the transmission side, and the process returns to step S11 (step S21).

  When it is determined in steps S16 and S19 that the reception level is lower than -10 dB, the process returns to step S11 without switching the transmission / reception selector switch 12, and the reception level of the antenna is measured again. It progresses to step S22. In step S22, it is determined whether or not the reception level is lower than a predetermined level such as −35 dB and the flag ANT Flag is “1”. If “No”, that is, it is determined that the reception level is higher than −35 dB or the flag ANT Flag is “0”, the process returns to step S1 to measure the reception level.

  If “Yes”, that is, the reception level is lower than −10 dB and the flag ANT Flag is “1” in step S22, a control signal S1 for switching the transmission / reception selector switch 12 to the reception side is generated. (Step S23). At the same time, the flag ANT Flag is cleared to “0” to store that the transmission / reception selector switch 12 is on the receiving side, and the process returns to step S11 (step S24). When it is determined in steps S16 and S19 that the reception level is lower than −10 dB, the process may immediately proceed to step S22 instead of returning to step S11.

  In this second embodiment having a diversity antenna, when both the received signal strengths of the antenna 1 and the antenna 2 are higher than −10 dB, the transmission / reception selector switch 12 switches to the transmitting side even during reception. It is done. When one of the reception signals of the antenna 1 and the antenna 2 is higher than −10 dB and the other is lower than −10 dB and higher than −35 dB, the reception signal of the antenna on the switched side, that is, the low level side is received. It is controlled to be input to the circuit. When the transmission / reception changeover switch 12 is on the transmission side and the reception signal of one antenna is lower than −35 dB, the transmission / reception changeover switch 12 is controlled to be switched to the reception side.

  FIG. 5 shows another example of a specific procedure of the switching control process of the transmission / reception selector switch 12 and the antenna selector switch 14 executed by the system control circuit 36 in the second embodiment.

  When this switching control process is started, the reception level is first measured by the signal level measurement circuit 35 (step S31). Next, it is determined whether or not the measured reception level is lower than a predetermined level such as -10 dB (step S32). When it is determined that the reception level is lower than −10 dB, the process proceeds to step S33, and it is determined whether or not the reception level is lower than −70 dB. If it is higher than -70 dB, the process returns to step S31. If it is lower than -70 dB, it is determined in step S34 whether it is higher than the reception level of the other antenna (B). When it is determined that it is higher than the reception level of the other antenna (B) (large B), the process proceeds to step S31 as it is, and when it is determined that it is lower than the reception level of the other antenna (B) (large A). After switching the antenna selector switch 14 in step S35, the process returns to step S31.

  Next, the reception level is measured again, and it is determined whether or not the measured reception level is lower than a predetermined level such as -10 dB (step S32). And when it determines with a receiving level being higher than -10 dB, it progresses to step S36 and it is determined whether it is low compared with the receiving level of the other antenna (B). Here, when it is determined that the reception level of the other antenna (B) is lower (small A), the process proceeds to step S37, and when it is determined that the reception level of the other antenna (B) is higher (small B). The process proceeds to step S39, where it is determined whether each reception level is lower than −10 dB.

  When it is determined that the reception level is higher than −10 dB, the process proceeds to step S41, the transmission / reception changeover switch 12 is switched to the transmission side, and the process returns to step S31. On the other hand, when it is determined in step S37 that the reception level is lower than -10 dB, the antenna changeover switch 14 is changed from antenna B to A in step S38, and when it is determined in step S39 that the reception level is lower than -10 dB. In step S40, the antenna selector switch 14 is switched from antenna A to B, respectively, and the process returns to step S31. According to this flow, when both the received signal strengths of the antenna A and the antenna B are higher than −10 dB, the transmission / reception selector switch 12 is switched to the transmission side even during reception. In the above flowchart, it is desirable to compare the reception levels of the two antennas during the preamble signal reception period at the beginning of the signal.

  Although the invention made by the present inventor has been specifically described based on the embodiment, the present invention is not limited thereto. For example, in the above-described embodiment, when the transmission / reception selector switch 12 is switched to the transmission side during reception, the gain of the power amplifier 13 is decreased during transmission. However, the gain of the amplifier in the preceding stage is decreased before the power amplifier 13. You may do it.

  In the second embodiment having the diversity antenna, when the strength of the received signal of one antenna is higher than a certain level, the transmission / reception selector switch 12 is set without measuring the received signal level of the other antenna. You may control to switch to the transmission side. This is because when the received signal of one antenna is as high as −10 dB, the level of the received signal of the other antenna is expected to be considerably high.

  In the above description, the case where the invention made mainly by the present inventor is applied to a transmitter / receiver used in a wireless LAN which is a field of use as a background thereof has been described. However, the present invention is not limited thereto, and Bluetooth is used. The present invention can also be applied to a transceiver having a communication function. The present invention is effective when used for a non-moving type transceiver that is not usually moved much.

It is a block diagram which shows one Example of the transmitter / receiver for wireless LAN suitable for applying this invention. 2 is a flowchart illustrating an example of a specific procedure of a switching control process of a transmission / reception selector switch executed by a system control circuit in the transceiver of the embodiment of FIG. 1. It is a block diagram which shows the other Example of the transmitter / receiver for wireless LAN suitable for applying this invention. 4 is a flowchart illustrating an example of a specific procedure of switching control processing of a transmission / reception selector switch executed by a system control circuit in the transceiver of the embodiment of FIG. 3. 4 is a flowchart showing another example of a specific procedure of the switching control process of the transmission / reception selector switch executed by the system control circuit in the transceiver of the embodiment of FIG. 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Antenna 12 Transmission / reception changeover switch 13 Transmission power amplifier 14 Antenna changeover switch 20 Transmission / reception part 21 Low noise amplifier 22 Mixer 30 Baseband part 32 Demodulation circuit 33 Modulation circuit 35 Measurement circuit 36 System control circuit (microcomputer)

Claims (6)

Transmission / reception used in a wireless LAN comprising a plurality of antennas, an antenna switching means for selecting one of the plurality of antennas, a transmission circuit, a reception circuit, a transmission / reception switching means, and a control circuit, and performing transmission and reception in a time division manner In the machine
The control circuit is
When the received signal strengths from the plurality of antennas are all equal to or higher than a preset first level,
Even during reception, the transmission / reception switching means is switched to the transmission circuit side, the reception signal is attenuated by the transmission / reception switching means, and input to the reception circuit,
And at the time of transmission, the gain of the amplifier in the transmission circuit is made lower than the gain when the intensity of the received signal is less than the first level,
When the strength of any one of the received signals from the plurality of antennas is higher than the first level, and the strength of any one of the received signals from the plurality of antennas is lower than the first level. Is a transceiver configured to control the antenna switching means to input a reception signal from an antenna whose intensity is lower than the first level to the reception circuit.   An antenna, a transmission circuit, a reception circuit, a transmission / reception switching means, and a control circuit. In this case, the transmitter / receiver is configured to switch the transmission / reception switching means to the transmission circuit side even at the time of reception, and attenuate the reception signal by the transmission / reception switching means to input to the reception circuit. .   When the intensity of the received signal is equal to or higher than the predetermined level, the control circuit lowers the gain of the amplifier in the transmitting circuit at the time of transmission lower than the gain when the intensity of the received signal is lower than the predetermined level. The transceiver according to claim 2.   Used in a radio communication system comprising a plurality of antennas, an antenna switching means for selecting one of the plurality of antennas, a transmission circuit, a reception circuit, a transmission / reception switching means, and a control circuit, and performing transmission and reception in a time division manner In the transceiver, the control circuit switches the transmission / reception switching means to the transmission circuit side even during reception when the intensity of the received signal from at least one antenna is equal to or higher than a preset first level. A transceiver configured to attenuate a signal by a transmission / reception switching unit and input the signal to the reception circuit.   When the intensity of the reception signal from at least one antenna is equal to or higher than the first level, the control circuit sets the gain of the amplifier in the transmission circuit at the time of transmission and the intensity of the reception signal is less than the first level. 5. The transmitter / receiver according to claim 4, wherein the transmitter / receiver is set to be lower than a gain of the case. In the control circuit, one of the received signals from the plurality of antennas has a strength higher than the first level, and any one of the received signals from the plurality of antennas has the first level. 5. The transceiver according to claim 4, wherein when the frequency is lower, the antenna switching unit is controlled to input a reception signal from an antenna whose strength is lower than the first level to the reception circuit. .

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