JP2007325234A - Radio communication equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide radio communication equipment having a function of attenuating a high-frequency reception signal when a strong input signal is received by an antenna. <P>SOLUTION: A plurality of threshold values of a threshold value 1 and a threshold value 2 lower than the threshold value 1 are used to control power-on/off of an LNA 111, namely, a high-frequency reception signal attenuation function. When a reception signal level exceeds the threshold value 1, the LNA 111 is powered off, and high-frequency reception signal attenuating operation is started. When the reception signal level is below the threshold value 2, the LNA 111 is powered on and the high-frequency reception signal attenuating operation is stopped but when the reception signal level is between the threshold value 1 and the threshold value 2, a power supply status of the LNA 111 is held. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a mobile terminal such as a mobile phone, or a wireless communication apparatus that performs mutual communication between wireless stations such as a wireless LAN (Local Area Network) or a PAN (Personal Area Network). The present invention relates to a radio communication apparatus capable of obtaining good reception performance in a signal range.

  More particularly, the present invention relates to a wireless communication apparatus that attenuates a high-frequency received signal when a strong input signal is received by an antenna, and in particular, a loss of a received frame occurs even in the vicinity of a switching point to a strong input signal. The present invention relates to a wireless communication apparatus having good reception performance without any problems.

  In recent years, broadband communication such as ADSL (Asymmetric Digital Subscriber Line) and FTTH (Fiber To The Home) has become widespread, and IP (Internet Protocol) of fixed telephones has been advanced.

  This flow is expected to spread to mobile phones, and one of them is the movement to install wireless LAN (Local Area Network) modules in mobile phones and to make IP (Internet Protocol) phones wireless. Since this wireless IP telephone communicates in real time, it is desired that the modulation accuracy and the packet error rate (PER) of the input signal received by the antenna are always good.

  By the way, in a wireless communication device such as a wireless LAN module, automatic gain control (Auto Gain Control: AGC) is generally performed in order to make the input level to the modulation / demodulation circuit constant. In addition, when a strong input signal is received by the antenna, if the input level to the modulation / demodulation unit cannot be kept constant by the AGC, a receiving circuit portion such as a low noise amplifier (LNA) or a frequency converter is used. There is a problem that the error rate deteriorates because the waveform of the received signal is distorted when passing. For example, when the mobile terminal is used in the vicinity of the base station, the input to the antenna becomes excessive, and the received signal is distorted every time the receiving circuit is processed. For this reason, when the input level exceeds a predetermined threshold value, the antenna is connected to the transmission system in spite of reception (however, when the antenna is shared in the transmission / reception system) (see, for example, Patent Document 1) ) Attenuate the high frequency received signal by turning off the LNA, providing a bypass path to the LNA, or inserting a variable attenuator between the antenna and the LNA (see, for example, Patent Document 2). In order to obtain good reception performance, the received signal is not distorted during down-conversion by frequency conversion.

  However, when such a high-frequency received signal attenuation function is used, switching between antennas and switches and LNA on / off control are frequently performed near the threshold at which the input signal level switches to a strong input. (Radio Frequency) The impedance of the circuit becomes unstable and adversely affects the receiving circuit, and a loss occurs in the received frame, which may degrade the PER. For example, in a wireless IP phone, the deterioration of PER causes a sound interruption.

Japanese Patent No. 3198894, paragraphs 0011-0012 JP 2002-335187 A, paragraphs 0004-0010

  An object of the present invention is to provide an excellent wireless communication apparatus capable of obtaining good reception performance in a wide reception signal range.

  A further object of the present invention is to provide an excellent wireless communication apparatus having a function of attenuating a high frequency received signal when a strong input signal is received by an antenna.

  A further object of the present invention is to provide an excellent wireless communication apparatus having a good reception performance without causing a loss of a received frame even in the vicinity of a switching point to a strong input signal.

  The present invention has been made in view of the above problems, and includes an antenna that receives a radio signal, a reception processing unit that receives and processes a reception signal of the antenna, and a reception signal level that detects a reception signal level of the antenna. A detection unit; a signal attenuation unit for attenuating a high-frequency reception signal in the antenna; and a control unit for controlling the attenuation operation of the high-frequency reception signal by the signal attenuation unit according to the detected reception signal level, Switches between a state in which the signal attenuator operates, a state in which the signal attenuator stops, and a state in which the operation of the signal attenuator continues or stops operating according to the received signal level. It is a communication device.

  In a wireless communication device such as a wireless LAN module, automatic gain control is generally performed to make the input level to the modulation / demodulation circuit constant. However, when a strong input signal is received by an antenna, AGC The input level to the modem cannot be kept constant. As a countermeasure, when the input level exceeds a predetermined threshold, a method of connecting the antenna to the transmission system regardless of the time of reception, or turning off the LNA, is used to attenuate the high frequency received signal, When down-converting by frequency conversion, the received signal is prevented from being distorted so as to obtain good reception performance.

  However, when such a high-frequency received signal attenuation function is used, switching between antennas and switches and LNA on / off control are frequently performed near the threshold at which the input signal level switches to a strong input. There is a possibility that the impedance of the circuit becomes unstable and adversely affects the receiving circuit, and a loss occurs in the received frame, thereby degrading the PER.

  Therefore, in the wireless communication apparatus according to the present invention, in addition to the state in which the signal attenuating unit operates and the state in which the signal attenuating unit stops, the signal attenuating unit continues to operate or stop operating, These states are appropriately switched according to the signal level.

  Specifically, when the received signal level exceeds a first threshold, the control unit starts the high-frequency received signal attenuation operation by the signal attenuating unit, and the received signal level is lower than the first threshold. When the received signal level falls between the first threshold value and the second threshold value, the operation state of the signal attenuating unit is maintained. To do.

  Therefore, even when the input signal level is in the vicinity of the threshold value for switching to a strong input, the switching of the antenna switch and the power on / off of the LNA are not frequently performed, and the impedance of the RF circuit is stabilized. The adverse effect on the receiving circuit is eliminated, and loss of the received frame and the accompanying deterioration of PER can be avoided.

  Here, the reception signal level detection unit may monitor the preamble portion of the reception frame and output RSSI (Received Signal Strength Indication).

  In addition, the reception processing unit usually includes a low noise amplification circuit that amplifies a weak signal attenuated by a propagation loss received by the antenna to an appropriate level, but the signal attenuation unit includes the low noise amplification circuit. The high frequency received signal can be attenuated by shutting off the power supply to the circuit.

  In addition, the wireless communication device further includes a transmission processing unit that processes transmission data and transmits it as a wireless signal via the antenna, and when the same antenna is shared by the transmission / reception processing unit via the transmission / reception changeover switch, The signal attenuating unit can perform the attenuating operation of the high frequency received signal by connecting the antenna to the transmission processing unit during the receiving operation.

  ADVANTAGE OF THE INVENTION According to this invention, the outstanding radio | wireless communication apparatus provided with the function to attenuate a high frequency received signal when a strong input signal is received with an antenna can be provided.

  Further, according to the present invention, it is possible to provide an excellent wireless communication apparatus having good reception performance without causing loss of a received frame even in the vicinity of a switching point to a strong input signal.

  When the input signal level is between the first threshold value and the second threshold value, the wireless communication apparatus according to the present invention keeps the power supply state of the LNA, so that the power supply of the LNA is frequently turned on and off. By avoiding the state, it is possible to prevent the impedance of the RF circuit from becoming unstable and adversely affect the receiving circuit, and to improve the loss of the received frame.

  Therefore, when the present invention is applied to a wireless communication apparatus that performs real-time communication such as a wireless IP phone, it is possible to avoid the occurrence of sound interruption.

  Other objects, features, and advantages of the present invention will become apparent from more detailed description based on embodiments of the present invention described later and the accompanying drawings.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 schematically shows a configuration of a high-frequency part mainly of a wireless communication apparatus 100 according to an embodiment of the present invention. The wireless communication device 100 is configured as a wireless LAN module, for example, but the gist of the present invention is not limited to this. Below, it demonstrates centering on the reception operation | movement of the said apparatus.

  The antenna 101 is configured to transmit and receive an RF signal in the 2.4 GHz band, for example, and is connected to the transmission / reception switching switch 102 and shared in the transmission / reception system.

  The transmission / reception switching switch 102 transmits the RF transmission signal transmitted from the transmission unit 103 to the antenna 101 when switching to the transmission system. Further, when switching to the reception system, the RF signal received by the antenna 101 is transmitted to the LNA 111.

  In the illustrated example, an SPDT (Single Pole Double Throw) switch is used as the transmission / reception switching switch 102. However, a DPDT (Double Pole Double Throw) switch may be used. Alternatively, two antennas may be mounted using two SPDT switches. In this case, since antenna diversity for combining or switching received signals of the respective antennas can be used, it is possible to perform good communication by selecting an antenna having a good communication state.

  The LNA 102 amplifies the weak signal attenuated by the propagation loss received by the antenna 101 to an appropriate level.

  The RF reception signal amplified by the LNA 111 is input to an RF band reception side bandpass filter (BPF) 112 to remove unnecessary signal components such as mobile phone call data.

  Next, the RF band variable gain amplifier 113 sets the output level appropriately by making the gain variable.

  The first frequency converter 114 uses an IF (Intermediate Frequency) frequency obtained by dividing a local frequency output from a local oscillator (not shown) by a PLL (Phase Lock Loop) circuit 122, The gain-amplified RF band received signal is frequency-converted (down-converted) into an IF signal.

  An IF band reception bandpass filter (BPF) 115 removes an image signal generated when down-converting from the RF band to the IF band.

  Next, the IF variable gain amplifier 116 sets the output level appropriately by making the gain variable.

  Next, the second frequency converter 117 further uses the baseband frequency obtained by dividing the local frequency output from the local oscillator (not shown) by the PLL circuit 123 to further convert the IF band received signal to the baseband. Convert frequency to signal. The baseband filter 118 removes unnecessary spurious generated during the frequency conversion.

  The modem 119 demodulates the input baseband signal.

  The input signal level calculation unit 120 monitors the output signal level of the baseband filter 118, and calculates the input signal level at the antenna 101 from this. This calculation is performed by monitoring the preamble portion of the received frame in the baseband, and is output as numerical data called RSSI (Received Signal Strength Indication: received signal strength).

  The LNA power supply control unit 121 performs on / off control of the power supply voltage to the LNA 111 according to the RSSI value.

  When the signal level received by the antenna 101 is too high, distortion occurs in the output of the RF band variable gain amplifier 113 or IF band variable gain amplifier 116, or the RF band variable gain amplifier 113 or IF band. Since the output level of the variable gain amplifier 116 is too high, the first frequency converter 114 or the second frequency converter 117 falls into an over-input state, resulting in distortion. As a result, normal modulation / demodulation section 119 cannot perform normal demodulation, resulting in a deterioration in reception sensitivity and an increase in packet error rate, and communication becomes impossible.

  In the illustrated wireless communication apparatus 100, when the RSSI value exceeds a predetermined level, the LNA power control unit 121 cuts off the power supplied to the LNA 111, thereby attenuating the high frequency received signal and distorting the received signal when down-converting. I am trying not to. When the RSSI value is too large, the high frequency reception signal can be similarly attenuated by connecting the transmission / reception switching switch 102 to the transmission unit 103 side instead of shutting off the power supply to the LNA 111.

  FIG. 2 shows an example of a processing procedure for performing power control for the LNA 111 according to the RSSI value in the LNA power control unit 121 in the form of a flowchart.

  In the wireless communication device 100 in the reception standby state, the transmission / reception switching switch 102 is set to the reception system, and the LNA 111 is in a power-on state.

  Here, when the preamble of the received frame is received (step S1), the RF received signal is down-converted into a baseband signal by each circuit module 111 to 118, and then the RSSI is calculated by the input signal level calculation unit 120 (step S1). S2).

  When receiving the RSSI from the input signal level calculator 120, the LNA power controller 121 compares it with a predetermined threshold (step S3). If the RSSI does not exceed the predetermined threshold, the LNA 11 is powered on (step S6). Thus, even when the input signal level to the antenna 101 is small, the received data can be demodulated normally (step S5).

  On the other hand, if the RSSI is larger than the predetermined threshold (Yes in step S3), the power of the LNA 111 is turned off to attenuate the high-frequency reception signal (step S4), and the signal level input to the subsequent reception circuit is lowered. . As a result, even when a strong input signal is received by the antenna 101, the received data can be normally demodulated (step S5).

  Here, when the power on / off of the LNA 111 is controlled with a single threshold as shown in FIG. 2, that is, when the attenuation function of the high-frequency reception signal is controlled, the input signal level is close to the threshold at which the input is switched to a strong input. Therefore, switching of the antenna switch and on / off control of the LNA 111 are frequently performed. For this reason, the impedance of the RF circuit becomes unstable and adversely affects the receiving circuit, and there is a problem that a loss occurs in the received frame, thereby deteriorating the PER.

  FIG. 3 shows the relationship between the input signal and the packet error rate (PER) in this case. When the input signal level is about the threshold value, the power supply of the LNA 111 is frequently turned on and off repeatedly, resulting in a loss of the received frame, and hence the PER is deteriorated.

  Furthermore, the difference that occurs when the LNA 111 is on and off is the input signal level so that there is no mismatch in the RSSI level that is output when the LNA 111 is powered on and off. It is corrected by the calculation unit 120.

  FIG. 4 shows a change in the power on / off operation of the LNA 111 and a change in the PER in association with the case where the input signal level changes with time.

  In a section where the input signal level is below the threshold value, the power supply of the LNA 111 is turned on, and even if the input signal level is small, data can be demodulated normally, so PER can be kept low.

  However, when the input signal level approaches the threshold value, the LNA 111 is frequently switched on and off due to vibration of the RSSI measurement result. When ON / OFF switching occurs, loss of received data occurs, and PER increases.

  Thereafter, when the input signal level greatly exceeds the threshold value, the power-off state of the LNA 111 is maintained. Therefore, even if the input signal level is large, data can be normally demodulated, and the PER can be kept low.

  As a countermeasure for the problem that on / off switching is frequently performed in the vicinity of the threshold value, power supply on / off of the LNA 111, that is, attenuation of a high-frequency received signal is performed using a plurality of threshold values of threshold value 1 and threshold value 2 lower than the threshold value 1. A method of controlling the function can be considered. That is, when the received signal level exceeds the threshold value 1, the power supply of the LNA 111 is turned off and the high frequency received signal is attenuated. When the received signal level is lower than the threshold value 2, the LNA 111 is turned on and the high frequency received signal is attenuated. Although the operation is stopped, the power state of the LNA 111 is maintained when the received signal level is between the threshold value 1 and the threshold value 2.

  FIG. 5 shows the relationship between the input signal and the packet error rate (PER) in this case. In a section where the input signal level is sandwiched between the threshold value 1 and the threshold value 2, the power control of the LNA 111 becomes a dead zone with respect to the RSSI, and the power supply of the LNA 111 can be either on or off depending on the previous state.

  For example, in the wireless communication apparatus 100 in the reception standby state, the transmission / reception switching switch 102 is set to the reception system and the LNA 111 is in the power-on state, but even if the input signal level exceeds the threshold 2, the LNA 111 However, when the input signal level further increases and exceeds the threshold value 1, the power supply of the LNA 111 is turned off. On the other hand, when the input signal level decreases once the input signal level increases and the power supply of the LNA 111 is once turned off, the power supply remains off when the value falls below the threshold 1, but further decreases to the threshold 2 The power is turned on when the value falls below.

  As a result, even when the input signal level is in the vicinity of the threshold value for switching to a strong input, the power on / off of the LNA 111 is not frequently switched, and the impedance of the RF circuit is stabilized, which adversely affects the receiving circuit. Is eliminated, and the loss of the received frame and the accompanying degradation of PER can be avoided.

  FIG. 6 shows an example of a processing procedure for the LNA power control unit 121 to perform power control on the LNA 111 using the threshold value 1 and the threshold value 2 in the form of a flowchart.

  In the wireless communication device 100 in the reception standby state, the transmission / reception switching switch 102 is set to the reception system, and the LNA 111 is in a power-on state.

  Here, when the preamble of the received frame is received (step S11), the RF received signal is down-converted to a baseband signal by each circuit module 111 to 118, and then the RSSI is calculated by the input signal level calculation unit 120 (step S11). S12).

  When receiving the RSSI from the input signal level calculation unit 120, the LNA power supply control unit 121 first compares the RSSI with the threshold value 1 (step S13). If the RSSI is larger than the threshold value 1 (Yes in step S13), the power of the LNA 111 is turned off to attenuate the high-frequency reception signal and lower the signal level input to the subsequent reception circuit. As a result, even when a strong input signal is received by the antenna 101, the received data can be normally demodulated (step S15).

  On the other hand, if the RSSI does not exceed the threshold 1 (No in step S13), the LNA power control unit 121 subsequently compares the RSSI with the threshold 2 (step S16).

  Here, when the RSSI is lower than the threshold value 2 (No in Step S16), the power supply of the LNA 11 is kept on (Step S17). Thereby, even when the input signal level to the antenna 101 is small, the received data can be demodulated normally (step S15).

  If the RSSI is larger than the threshold value 2 (Yes in step S16), the frame is received as it is without switching the power supply of the LNA 111 on (step S15). As a result, even when the input signal level is in the vicinity of the threshold value for switching to a strong input, the power on / off of the LNA 111 is not frequently switched, and the impedance of the RF circuit is stabilized, which adversely affects the receiving circuit. Is eliminated, and the loss of the received frame and the accompanying degradation of PER can be avoided.

  The present invention has been described in detail above with reference to specific embodiments. However, it is obvious that those skilled in the art can make modifications and substitutions of the embodiment without departing from the gist of the present invention.

  In the present specification, the embodiment applied to the wireless LAN module has been mainly described, but the gist of the present invention is not limited to this. Also, when the received signal level is too high, the high frequency received signal can be attenuated by shutting off the power supply to the LNA immediately after the antenna. Of course, the antenna is switched to the connection to the transmission system, or other methods The high frequency received signal may be attenuated by

  In short, the present invention has been disclosed in the form of exemplification, and the description of the present specification should not be interpreted in a limited manner. In order to determine the gist of the present invention, the claims should be taken into consideration.

FIG. 1 is a diagram schematically showing a configuration of mainly a high frequency part of a radio communication apparatus 100 according to an embodiment of the present invention. FIG. 2 is a flowchart showing an example of a processing procedure for performing power control on the LNA 111 according to the RSSI value in the LNA power control unit 121. FIG. 3 is a diagram showing the relationship between the input signal and the packet error rate (PER) when the LNA 111 is switched on / off with a single threshold. FIG. 4 shows the change in the power on / off operation of the LNA 111 and the change in the PER accompanying the assumption that the input signal level changes with time. FIG. 5 is a diagram showing the relationship between the input signal and the packet error rate (PER) when the power supply on / off of the LNA 111 is switched using the threshold value 1 and the threshold value 2. FIG. 6 is a flowchart showing an example of a processing procedure for performing power control in the LNA power control unit 121 using the threshold value 1 and the threshold value 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Wireless communication apparatus 101 ... Antenna 102 ... Transmission / reception switching switch 103 ... Transmission part 111 ... Low noise amplifier circuit (LNA)
112: Band pass filter (BPF)
DESCRIPTION OF SYMBOLS 113 ... Variable gain amplifier 114 ... 1st frequency converter 115 ... Band pass filter (BPF)
DESCRIPTION OF SYMBOLS 116 ... Variable gain amplifier 117 ... 2nd frequency converter 118 ... Baseband filter 119 ... Modulator / demodulator 120 ... Input signal level calculation part 121 ... LNA power supply control part 122 ... PLL circuit 123 ... PLL circuit

Claims (5)

An antenna for receiving radio signals;
A reception processing unit for receiving and processing a reception signal of the antenna;
A received signal level detector for detecting a received signal level of the antenna;
A signal attenuator for attenuating a high-frequency received signal in the antenna;
A control unit that controls the attenuation operation of the high-frequency reception signal by the signal attenuation unit according to the detected reception signal level,
The control unit switches between a state in which the signal attenuating unit operates, a state in which the signal attenuating unit is stopped, and a state in which the operation of the signal attenuating unit is continued or stopped according to a received signal level.
A wireless communication apparatus. The control unit starts a high-frequency received signal attenuation operation by the signal attenuating unit when the received signal level exceeds a first threshold, and when the received signal level falls below a second threshold lower than the first threshold, Attenuating the high frequency received signal by the signal attenuating unit, and holding the operating state of the signal attenuating unit when the received signal level is between the first threshold and the second threshold;
The wireless communication apparatus according to claim 1. The received signal level detection unit monitors a preamble portion of the received frame and outputs an RSSI (Received Signal Strength Indicator).
The wireless communication apparatus according to claim 1. The reception processing unit includes a low noise amplification circuit that amplifies a weak signal attenuated by a propagation loss received by the antenna to an appropriate level,
The signal attenuator performs an attenuation operation of a high-frequency received signal by shutting off a power supply to the low noise amplifier circuit.
The wireless communication apparatus according to claim 1. A transmission processing unit that processes transmission data and transmits it as a radio signal via the antenna; and a transmission / reception switching switch that connects the antenna to either the transmission processing unit or the reception processing unit,
The signal attenuation unit performs an attenuation operation of a high-frequency reception signal by connecting the antenna to the transmission processing unit during a reception operation.
The wireless communication apparatus according to claim 1.

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