JP4378263B2 - Receiver - Google Patents

Description

  The present invention relates to a receiving apparatus, and more particularly to an AGC control method in diversity reception.

  Diversity reception using a plurality of antennas is known. In particular, in the case of mobile reception or the like in which the received signal is susceptible to fading that greatly varies with time, it is known that reception characteristics are improved by providing or selecting or combining a plurality of antennas. However, when the signal from any one of the plurality of antennas is extremely small, the noise is amplified by the operation of automatic gain control (AGC), and further, the effects of the noise are synthesized by combining the signals from each antenna. May generate a composite wave that is greatly affected by. For example, FIG. 9 is an example in the case of receiving with two antennas (A and B). The received signal from the antenna A has sufficient power, and the signal from the antenna B has a very small received power. AGC attenuates a signal if the received power is very large, amplifies the signal if the received power is very small, and controls the signal level to be substantially constant. After control by AGC, the received signal from antenna A hardly changes, but the received signal from antenna B is greatly amplified, and noise is also amplified at the same time. Therefore, these combined waves are signals that are greatly affected by noise.

  As means for solving this problem, there are the following conventional examples relating to a receiving apparatus for preventing deterioration of the signal-to-noise ratio at the time of diversity reception. FIG. 10 shows an in-phase combined space diversity antenna circuit, in which filters 53 and 56 for taking out received waves, level detectors 54 and 55, attenuators 51 and 58, and a control circuit 52 are provided. When the attenuators 51 and 58 are normal, the attenuation is 0. For example, when the received power of the antenna 1 is reduced due to fading and the level detected by the detector 54 is lower than the standard level by 50 dB or more, the attenuation of the attenuator 51 The control circuit 52 performs control so that the noise power is hardly input to the synthesizer 59. As a result, the synthesizer 59 does not synthesize the received wave received by the antenna 1 and noise, so that the S / N does not deteriorate. Such a technique is described in Patent Document 1.

As another prior art, according to Patent Document 2, in the diversity system as shown in FIG. 11, when there is no difference in the received input signal, the output of the logic circuit 75 is synthesized by the signal switching unit 76. Is output. If there is a difference between the received input signals, the service signal with the lower received input is disconnected by the switch 77 based on the information of the received wave comparator 72, and only the service signal with the higher received input is taken out. Also, when an error or out of synchronization occurs in the demodulators 73 and 74, this information is sent to the logic circuit 75 to operate the switch 77 so as to prevent S / N deterioration due to signal synthesis. Further, according to Patent Document 3, it is proposed that a multiplier is provided and a multiplication signal generated so as to be proportional to the input signal level is used.
JP-A-60-149234 Japanese Patent Laid-Open No. 60-117938 Japanese Patent Laid-Open No. 8-23098

  Thus, a technique for preventing S / N degradation in diversity reception is conventionally known. However, since it is necessary to know the reception state of the signal from each antenna as in the above-described device, it is necessary to provide a demodulation circuit for each branch, which has a problem that the circuit scale and power consumption increase. .

  The present invention has been made in view of such a situation, and an object of the present invention is to provide a receiving apparatus that can reduce the hardware scale and power consumption by using a single demodulation circuit.

  The present invention solves these problems, and each invention has the following techniques. According to a first aspect of the present invention, there is provided a plurality of antennas for receiving modulated signals, and an automatic gain for automatically controlling a gain of the input high frequency signal by comparing a high frequency signal level received from the plurality of antennas with a reference voltage level. Control means (AGC), synthesis means for synthesizing each high-frequency signal, one demodulation means for demodulating the synthesized signal, reception quality detection means for detecting the reception quality of the data demodulated by the demodulation means, And control means for controlling IF AGC for each antenna in accordance with the reception quality detected by the reception quality detection means.

  Further, according to a second invention, in the receiving apparatus of the first invention, when the reception quality detecting means determines that the quality of the combined received signal is poor, the gain by the automatic gain control means in each antenna Detecting the control level, comparing the detected gain control levels, and minimizing the amplification factor of the IF signal by the control means for a high-frequency signal having a large amplification factor when the level difference exceeds a predetermined value It is possible to minimize IF AGC of a branch including a lot of noise.

  Further, in a third aspect of the present invention, in the receiving apparatus of the second aspect, after the IF signal gain is minimized by the control means, the received quality detecting means detects the quality of the combined received signal, When the improvement of the signal quality is not observed, the gain control by the automatic gain control means is restarted, and when the improvement is not achieved by the IF AGC minimization, it can be restored.

  According to a fourth aspect of the present invention, in the receiving apparatus of the first aspect, the control means can perform gain control in units of steps, and the quality of the received signal synthesized by the reception quality detection means can be improved. When it is determined to be inferior, the gain control level by the automatic gain control means in each antenna is detected, the detected gain control levels are compared, and if the level difference exceeds a predetermined value, a high frequency with a large amplification factor For the signal, the control means controls the amplification factor of the IF signal in units of steps and suppresses IF AGC in units of steps, and suppresses IF AGC of a branch containing a lot of noise in units of steps. Can do.

  In addition, in a fifth aspect of the present invention, in the receiving apparatus according to the fourth aspect of the invention, the control means detects the quality of the received signal synthesized by the reception quality detection means every time the gain is controlled in units of steps, Control is performed so that the IF signal amplification factor provides the best signal quality, and the optimum value of BER can be searched for during step-by-step suppression.

  According to a sixth aspect of the present invention, in the receiving apparatus according to the fifth aspect of the present invention, the RF AGC control level in which the gain is controlled by the automatic gain control means after the control means has controlled the amplification factor to obtain the best received signal quality. Is detected each time a predetermined time elapses, and IF AGC gain is equal to or less than a predetermined value (= received signal level becomes stronger), IF AGC control also resumes gain control by automatic gain control means The return process 1 can be performed.

  Further, according to a seventh aspect of the present invention, in the receiving apparatus of the fifth aspect, the RF AGC control level in which the gain is controlled by the automatic gain control means after the control means controls the amplification factor to obtain the best received signal quality. Is detected every time a predetermined time elapses, and when the RF AGC amplification factor falls below a predetermined value, the received signal quality is detected by the reception quality detection means, and a reception quality of a predetermined level or higher is obtained. The control means controls the gain in units of steps and relaxes the suppression of IF AGC in units of steps, so that the recovery process 2 can be performed.

  In addition, according to an eighth aspect of the invention, in the receiving device of the seventh aspect, the control means detects the quality of the reception signal synthesized by the reception quality detection means every time the gain is controlled in units of steps, Control is performed so that the IF signal amplification factor provides the best signal quality, and the optimum value of BER can be searched for when the suppression is reduced in units of steps.

  According to the present invention described above, when the signal power from a specific antenna is low in diversity reception, the signal quality is reduced due to noise amplification to prevent deterioration of signal quality due to noise amplification. be able to. Furthermore, by using one demodulation circuit, it is possible to reduce the hardware scale and power consumption.

The best mode for carrying out the present invention will be described.
An embodiment of the receiving apparatus of the present invention will be described below with reference to FIGS.

  Example 1 will be described. The present embodiment is an embodiment of the first invention, and FIG. 1 shows an example of the configuration of the embodiment of the receiving apparatus according to the present invention. Here, an example in which two antennas are used is shown, but a configuration in which the number of antennas and tuners is further increased may be employed. Broadcast waves are received from the antennas 1 and 2, respectively, and the channel selection frequency is set by the channel selection units 3 and 4 provided in the tuner unit. The reception signal is controlled by the AGC circuits 5 and 6 so that the output level becomes constant even when the input signal level changes, and is synthesized by the synthesis means 10. The synthesized signal is digitally converted by the A / D converter 11, converted to a complex baseband signal by the quadrature detection circuit 12, and output as received data via the FFT circuit 13, the equalization circuit 14, and the error correction circuit 15. Is done.

  Details of the AGC circuit will be described. FIG. 2 is an internal configuration diagram of the AGC circuits 5 and 6. Although only the AGC circuit 5 is shown here, the AGC circuit 6 has the same configuration. The RF signal (high frequency signal) input to the AGC circuit 5 is amplified by the RF AGC 21 and then passes through the mixer 23, the BPF (band pass filter) 22, and the IF amplifier 25 and is output as an IF signal (intermediate frequency signal). Is done. The IF amplifier output is input to the level detection circuit 26, and a DC voltage corresponding to the IF output amplitude level is output. With this voltage, the RF AGC control unit 27 controls the amplification factor of the RF AGC 21. Further, the output of the IF amplifier 25 is input to the IF AGC 28 and input to the A / D converter 11 and the quadrature detection circuit 12. The IF AGC control circuit 29 controls the amplification factor of the IF AGC 28 according to the output amplitude level of the quadrature detection circuit 12. The power detection circuit 7 detects the control level of the RF AGC control circuit 27 and the IF AGC control circuit 29 and obtains the level of received power. Normally, the RF AGC control circuit 27 and the IF AGC control circuit 29 perform automatic control so that the output level is always substantially constant. However, the IF AGC control circuit 29 can be controlled by the control unit 9. It has become.

  In the receiving apparatus of the present embodiment, description will be made of IF AGC minimization (second invention) of a branch including a lot of noise and a case where improvement is not achieved by IF AGC minimization (third invention). 3 and 4 are examples of flowcharts in the present embodiment. The reception quality detection means 19 in FIG. 1 detects the reception quality of the signal after combining the signals received from the antennas (S301). As the reception quality to be detected, C / N (Carrier to Noise Ratio), BER (Bit Error Rate), and the like can be considered. In this example, BER is obtained from the output of the error correction circuit 15. The reception quality detection unit 19 determines whether or not the reception state is inferior (S302). In FIG. 3, as an example of this determination, if the acquired BER is greater than 1.0E-3, it is determined to be poor, and otherwise, it is determined not to be bad. When it is determined that the quality of the synthesized received signal, that is, the BER is poor, the information is transmitted to the control unit 9. The control unit 9 detects the AGC control level for the signal of each antenna by the power detection circuits 7 and 8 prepared for each antenna (S303, S304). If the control level of the AGC circuit 5 for the antenna 1 is P and the control level of the AGC circuit 6 for the antenna 2 is Q, it is compared whether or not the difference between P and Q is a predetermined value (predetermined value a) or more ( S305). For example, when the reception power of the antenna 1 is strong and the reception power of the antenna 2 is small, the amplification factor by the AGC circuit 5 is small and the amplification factor by the AGC circuit 6 is large. When the difference between the amplification factors is equal to or greater than a predetermined value, it can be determined that the reception power of the antenna 2 is very small with respect to the antenna 1, and the amplification factor of the reception signal of the antenna 2 is largely controlled. In addition, it is thought that noise is also amplified. Therefore, the control unit 9 sends a control signal to the IF AGC control circuit of the AGC circuit 6 so as to minimize the amplification factor so that only the signal from the antenna 1 is input to the receiver 2. Reduces the effects of noise caused by signal amplification. That is, when the difference between P and Q is equal to or larger than a predetermined value, it is determined which amplification factor is larger (S306). When P, that is, the amplification factor for the signal of the antenna 1 is large, the IF AGC of the antenna 1 is determined. The control level is minimized (S307). Q, that is, if the amplification factor for the signal of the antenna 2 is large, the IF AGC control level of the antenna 2 is minimized (S308).

  Thereafter, the reception quality detection means 19 acquires a BER every time a predetermined time elapses. When the BER deteriorates below a predetermined value, it is considered that the reception signal level of each antenna has changed, and the reception state may be improved by releasing the suppression for the currently suppressed signal level. Therefore, the IF AGC of the antenna 2 controlled by the control unit 9 is returned to automatic control. FIG. 4 is an example of a flowchart of this control. In the state where the IF AGC control level is suppressed, the reception quality detection means 19 detects the BER (S401). The reception state detection means 19 determines whether or not the reception state is inferior (S402). If it is determined that the reception state is inferior, the IF AGC control that has been suppressed is returned to automatic control (S403). In this way, it is possible to always perform control in a direction in which the reception state is improved with respect to changes in the reception signal level of each antenna due to the influence of fading.

  In the receiving apparatus of the present embodiment, description will be given of suppressing IF AGC of a branch including a lot of noise in units of steps (fourth invention) and searching for an optimum value of BER when suppressing in units of steps (fifth invention). To do. In the control of IF AGC by the control unit 9, it has been described that the amplification factor is minimized, but the amplification factor may be changed in units of steps. For example, when the difference between the AGC amplification factors for the signals of the respective antennas is equal to or greater than a predetermined value, the control unit 9 suppresses the amplification factor by one step with respect to the IF AGC control circuit of the AGC circuit 6. Every time one step is suppressed, the reception quality detection means 19 detects the BER. If the BER improves, the signal is further suppressed by one step, and the reception quality detection means 19 detects the BER. When the BER deteriorates, the suppression level is controlled so as to return to the state before the deterioration, that is, one step before. By controlling in units of steps in this way, it is possible to adjust to an AGC control level that optimizes the BER.

  5 and 6 are examples of flowcharts in the above embodiment. It is determined whether the difference between the AGC gains for the signals of the respective antennas is greater than or equal to a predetermined value (S505). If the difference is greater than or equal to the predetermined value, it is determined which of the antennas has a higher gain for the signal (S506). . For example, when the IF AGC control level of the antenna 1 is greatly amplified, the IF AGC control level for the antenna 1 is suppressed by one step (S507), and it is determined whether or not the BER is improved (S508). In the case of improvement, the IF AGC control level is further suppressed by one step (S507), and the BER is confirmed (S508). This is repeated, and if the BER deteriorates, the IF AGC control level is returned to the position where the BER was the best (S509).

  In FIG. 6, in a state where the IF AGC control level is suppressed, the reception quality detection means 19 acquires the BER (S601), and determines whether the reception state has deteriorated (S602). When the BER is deteriorated, the IF AGC suppression is released step by step (S603), and the operation of determining whether the BER is improved (S604) is repeated to control the IF AGC control level to a position where the BER is best. (S605).

  A description will be given of a method (sixth invention) in which the reception level of the suppressed signal is improved and the suppression is canceled in the receiving apparatus of the present embodiment. In mobile reception, the reception state changes significantly, and the level of the signal received by each antenna also changes every moment. For this reason, if suppression is always performed in order to suppress noise amplification, it becomes impossible to cope with changes in the reception state. Even during IF AGC suppression, RF AGC automatically performs gain control, so when the received signal level increases, the RF AGC amplification level decreases and changes in the reception state are detected. can do. Therefore, after the suppression, the RF AGC control level is detected every time a predetermined time elapses. If it is determined that the detected RF AGC gain has dropped below a predetermined value and the received signal level has increased, the suppression of IF AGC is canceled and automatic control is resumed.

  FIG. 7 is an example of a flowchart of the above procedure. Here, an example in which the IF AGC control level is suppressed for the signal of the antenna 1 is shown, but the same applies to the case of the antenna 2. In the IF AGC suppression state, the RF AGC control level is detected by the power detection circuit (S701). Next, it is determined whether or not the RF AGC control level is lowered (S702). If the RF AGC is lowered, it is considered that the received power has increased. Therefore, the suppression of IF AGC is canceled, and automatic control is resumed (S703).

  In the receiving apparatus of the present embodiment, IF AGC suppression cancellation can be performed in units of steps (inventions 7 and 8). FIG. 8 is an example of a flowchart of this procedure. For example, when the RF AGC control level is detected (S801) and the RF AGC control level is lowered, that is, when it is determined that the received signal level has increased (S802), the suppression of IF AGC is released in units of steps. That is, the IF AGC amplification factor is increased in steps (S804). Each time the IF AGC amplification factor is changed, the reception quality detection means 19 determines whether or not the BER has been improved (S804). If the BER is improved, the amplification factor is further increased (S803), If this happens, the state before the deterioration is restored (S805). In this way, it is possible to adjust to the IF AGC control level at which the reception state is optimal.

It is a functional block diagram which shows the receiver of an Example. It is a functional block diagram of an AGC circuit in the receiving apparatus of the embodiment. It is the flowchart 1 in the receiver of an Example. It is the flowchart 2 in the receiver of an Example. FIG. 3 is a flowchart 3 of the receiving apparatus according to the embodiment. FIG. 4 is a flowchart 4 of the receiving apparatus according to the embodiment. FIG. 6 is a flowchart 5 of the receiving apparatus according to the embodiment. FIG. 6 is a flowchart 6 of the receiving apparatus according to the embodiment. It is a figure for demonstrating the operation | movement of AGC. It is a functional block diagram of the conventional receiver. It is a functional block diagram of the conventional receiver.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Antenna 3, 4 Channel selection part 5, 6 AGC circuit 7, 8 Power detection circuit 9 Control part 10 Synthesis | combination means 11 A / D converter 12 Quadrature detection circuit 13 FFT circuit 14 Equalization circuit 15 Error correction circuit 16 OSC
17 Synchronous Reproduction Circuit 18 Pilot Interpolation Circuit 19 Reception Quality Detection Means 21 RF AGC
22 Band pass filter 23 Mixer 24 OSC
25 IF amplifier 26 Level detector 27 AGC control circuit 28 IF AGC
29 IF AGC control circuit 100 demodulation means

Claims (7)

A plurality of automatic gain control means for controlling the gain of the input high frequency signal from the antenna that receives the modulated signal, and a combining means for combining the high frequency signals output from the automatic gain control means to obtain a combined received signal And demodulating means for demodulating the combined received signal, receiving quality detecting means for detecting the receiving quality of the data demodulated by the demodulating means, and control means for controlling the automatic gain obtaining means, Each of the automatic gain control means includes a high frequency gain control means and an intermediate frequency gain control means, and the high frequency gain control means compares the high frequency signal level of the input high frequency signal from the antenna with a reference voltage level, and the input high frequency gain control means. The gain of the intermediate frequency signal is automatically controlled, and the gain of the intermediate frequency signal is automatically controlled by the control means. , Gain control of forcibly intermediate frequency signal according to the reception quality in which the reception quality detection means has detected is suppressed,
The control means compares the gain control levels obtained by detecting the gain control level of the automatic gain control means in each antenna when the quality of the combined received signal detected by the reception quality detection means is poor. A receiving apparatus for minimizing an amplification factor of an intermediate frequency signal by the intermediate frequency gain control means for a high frequency signal having a large amplification factor when the difference becomes a predetermined value or more . The receiving device according to claim 1,
The control means resumes automatic gain control by the intermediate frequency gain control means when there is no improvement in the quality of the combined received signal detected by the reception quality detection means after minimizing the amplification factor of the intermediate frequency signal. receiving apparatus characterized by causing. A plurality of automatic gain control means for controlling the gain of the input high frequency signal from the antenna that receives the modulated signal, and a combining means for combining the high frequency signals output from the automatic gain control means to obtain a combined received signal And demodulating means for demodulating the combined received signal, receiving quality detecting means for detecting the receiving quality of the data demodulated by the demodulating means, and control means for controlling the automatic gain obtaining means, Each of the automatic gain control means includes a high frequency gain control means and an intermediate frequency gain control means, and the high frequency gain control means compares the high frequency signal level of the input high frequency signal from the antenna with a reference voltage level, and the input high frequency gain control means. The gain of the intermediate frequency signal is automatically controlled, and the gain of the intermediate frequency signal is automatically controlled by the control means. , Gain control of forcibly intermediate frequency signal according to the reception quality in which the reception quality detection means has detected is suppressed,
The intermediate frequency gain control means can perform gain control on a step-by-step basis, and when the quality of the combined reception signal detected by the reception quality detection means is poor, the control means When the gain control level obtained by detecting the gain control level of the automatic gain control means is compared and the level difference becomes a predetermined value or more, the automatic gain control by the intermediate frequency gain control means is stopped, A receiving apparatus comprising: controlling an amplification factor for a high-frequency signal having a large amplification factor in units of steps, and performing suppression control of an intermediate frequency gain control unit in units of steps . The receiving device according to claim 3 ,
Each time the control means performs suppression control of the intermediate frequency gain control means in units of steps, the reception quality detection means detects the quality of the synthesized reception signal, and the detected quality of the synthesized reception signal is the best step, The receiving apparatus according to claim 1 , wherein the intermediate frequency gain control means performs gain control . The receiving device according to claim 4,
The control means is controlled every time a control level by the high frequency gain control means elapses after a predetermined time after controlling to an amplification factor at which the quality of the combined received signal is the best, and the amplification factor by the high frequency gain control means is a predetermined value. In the case of the following, the receiving apparatus restarts the gain control by the intermediate frequency gain control means . The receiving device according to claim 4 ,
The control means is controlled every time a control level by the high frequency gain control means elapses after a predetermined time after controlling to an amplification factor at which the quality of the combined received signal is the best, and the amplification factor by the high frequency gain control means is a predetermined value. When the reception quality detecting means detects the reception quality of the combined received signal of a predetermined level or higher, the gain control is performed in units of steps, and the suppression of the intermediate frequency gain control means in steps is alleviated. A receiving device. The receiving apparatus according to claim 6 , wherein
Each time the control means performs gain control in units of steps, the reception quality detection means detects the quality of the combined reception signal so that the reception signal quality obtained by the quality is the best amplification factor of the intermediate frequency signal. A receiving device that controls the receiving device.

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