WO2021205558A1

WO2021205558A1 - Receiver and automatic gain control method

Info

Publication number: WO2021205558A1
Application number: PCT/JP2020/015774
Authority: WO
Inventors: 山崎　誠
Original assignee: 三菱電機株式会社
Priority date: 2020-04-08
Filing date: 2020-04-08
Publication date: 2021-10-14
Also published as: JP7275383B2; JPWO2021205558A1

Abstract

Provided is a receiver in which an AGC circuit (20) includes a saturation level detection unit (23), a gain setting unit (22), a gain adjustment unit (21), and a parameter setting unit (24). The saturation level detection unit (23) detects the saturation level of a digital signal output from an A/D converter (10). The gain setting unit (22) sets the gain used in adjustment of the amplitude level of the digital signal on the basis of the saturation level detected by the saturation level detection unit (23). The gain adjustment unit (21) adjusts the amplitude level of the digital signal in accordance with the gain set by the gain setting unit (22). The parameter setting unit (24) sets a parameter used in the saturation level detection unit (23) on the basis of the amplitude level of the digital signal output from the A/D converter (10).

Description

Receiver and automatic gain control method

This disclosure relates to a receiver and an automatic gain control method.

In receivers used in wireless communication equipment, radar, GPS (Global Positioning System), etc., the dynamic range of signal reception depends on the performance of each circuit (amplifier, mixer, ADC (Analog-Digital Converter), etc.) that composes the receiver. Is restricted. Therefore, in order to realize a high dynamic range, automatic gain control (hereinafter referred to as "AGC (Automatic Gain Control)") for adjusting the signal level (amplitude) of the received signal may be performed.

AGC has a function of attenuating the signal level of the received signal when a high power signal is received and amplifying the signal level of the received signal when a low power signal is received. This function may be performed on a digital signal digitally converted by an A / D (Analog / Digital) converter.

In Japanese Patent Application Laid-Open No. 2016-25561, in a variable gain amplifier corresponding to an AGC circuit, the amplitude of a signal is obtained at two measurement timings, and the saturation of the variable gain amplifier is detected and the gain is set by comparing the two. The method is disclosed (see Patent Document 1).

Japanese Unexamined Patent Publication No. 2016-25561

In a receiver equipped with an AGC circuit, it is required to realize stable signal processing for each environment (location, time, application, etc.) in which the receiver is used. However, if the parameters used for AGC processing are fixed (for example, preset fixed values), the signal amplitude adjustment by AGC becomes insufficient and stable depending on the environment in which the receiver is used. Signal processing may not be possible.

The present disclosure has been made to solve such a problem, and an object of the present disclosure is to provide a receiver and an automatic gain control method that enable stable signal processing for each environment in which the signal is used. ..

The receiver of the present disclosure includes an A / D converter that converts a received signal into a digital signal, and an AGC circuit that adjusts the amplitude level of the digital signal. The AGC circuit includes a saturation level detection unit, a gain setting unit, a gain adjustment unit, and a parameter setting unit. The saturation level detection unit detects the saturation level of the digital signal output from the A / D converter. The gain setting unit sets the gain used for adjusting the amplitude level of the digital signal based on the saturation level detected by the saturation level detection unit. The gain adjusting unit adjusts the amplitude level of the digital signal according to the gain set by the gain setting unit. The parameter setting unit sets the parameters used in the saturation level detection unit based on the amplitude level of the digital signal output from the A / D converter.

Further, the automatic gain control method of the present disclosure is an automatic gain control method of a receiver, which includes a step of detecting a saturation level of a digital signal output from an A / D converter that converts a received signal into a digital signal. It is used to set the parameters used to detect the saturation level based on the amplitude level of the digital signal output from the A / D converter, and to adjust the amplitude level of the digital signal based on the detected saturation level. It includes a step of setting the gain and a step of adjusting the amplitude level of the digital signal according to the set gain.

According to the above receiver and automatic gain control method, the parameters used for detecting the saturation level of the digital signal are set based on the amplitude level of the digital signal output from the A / D converter. It is possible to detect the saturation level according to the nature of the received signal regardless of the environment in which it is used.

Therefore, according to the present disclosure, it is possible to provide a receiver and an automatic gain control method that enable stable signal processing for each environment in which it is used.

It is a block diagram which shows the structure of the receiver according to Embodiment 1 of this disclosure. It is a block diagram which shows the structure of the parameter setting part shown in FIG. It is a timing chart which shows the setting example of a parameter. It is a block diagram which shows the structure of the saturation level detection part shown in FIG. It is a timing chart which shows the detection example of the saturation level. It is a figure which shows an example of the hardware composition of the AGC circuit. It is a flowchart which shows an example of the procedure of the processing executed in the AGC circuit. It is a figure which shows the structure of the parameter setting part in Embodiment 2. It is a timing chart which shows an example of the case where the threshold value of the amplitude determination part rises. It is a timing chart which shows an example of the case where the threshold value of the amplitude determination part decreases. It is a figure which shows the structure of the parameter setting part in Embodiment 3. FIG. It is a timing chart which shows the parameter setting example by the parameter setting part of Embodiment 3. It is a block diagram which shows the structure of the receiver according to Embodiment 4. It is a figure which shows the structure of the parameter setting part and the parameter update timing adjustment part in the AGC circuit shown in FIG. It is a timing chart which shows the change example of a parameter update timing. It is a figure explaining the effect by extending the interval of a parameter update timing. It is a timing chart which shows the change example of a parameter update timing. It is a figure explaining the effect by shortening the interval of a parameter update timing.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Hereinafter, a plurality of embodiments will be described, but it is planned from the beginning of the application that the configurations described in the respective embodiments are appropriately combined. The same or corresponding parts in the drawings are designated by the same reference numerals, and the description thereof will not be repeated.

Embodiment 1.
FIG. 1 is a block diagram showing a configuration of a receiver according to the first embodiment of the present disclosure. With reference to FIG. 1, the receiver 100 includes a receiving unit 30 and a demodulating unit 40. The receiving unit 30 includes an A / D converter 10 and an AGC circuit 20.

The A / D converter 10 samples an analog received signal at a predetermined frequency and converts it into a discrete digital signal. The AGC circuit 20 is configured to receive a digital signal output from the A / D converter 10 and automatically adjust the amplitude level of the digital signal. The demodulation unit 40 demodulates the digital signal whose amplitude level has been adjusted by the reception unit 30, and restores the signal transmitted from the transmitter (not shown).

The AGC circuit 20 includes a gain adjusting unit 21, a gain setting unit 22, a saturation level detecting unit 23, and a parameter setting unit 24. The gain adjusting unit 21 receives the digital signal output from the A / D converter 10 and follows the gain set by the gain setting unit 22 (sometimes referred to as “gain”, “amplification factor”, etc.). , Adjust the amplitude level of the received digital signal. In the following, the digital signal output from the A / D converter 10 may be referred to as an "input signal" when viewed from the AGC circuit 20. The digital signal whose amplitude level has been adjusted by the gain adjusting unit 21 is output to the demodulation unit 40.

The gain setting unit 22 receives the saturation level (described later) of the input signal detected by the saturation level detection unit 23 from the saturation level detection unit 23, and sets the gain of the gain adjustment unit 21 based on the saturation level. For example, the relationship between the saturation level of the input signal and the gain of the gain adjusting unit 21 is obtained in advance, and the gain setting unit 22 converts the saturation level received from the saturation level detecting unit 23 into a gain using this relationship. Output to the gain adjustment unit 21. The relationship between the saturation level of the input signal and the gain is associated so that, for example, the higher the saturation level, the smaller the gain.

The saturation level detection unit 23 detects the saturation level of the digital signal (input signal) output from the A / D converter 10. The saturation level is a signal level at which the receiver 100 is not saturated, and in the present embodiment, the moving average value of the digital signal (input signal) output from the A / D converter 10 is defined as the “saturation level”.

That is, the AGC adjusts the gain so that the gain becomes small when the amplitude level of the input signal is high so that the receiver operates within the saturation level, but when a sudden amplitude fluctuation occurs due to disturbance or the like. , Excessive gain adjustment may occur. Therefore, in the present embodiment, the moving average value of the input signal is calculated, and this moving average value is used as the state value that characterizes the saturation level of the receiver 100. Then, the gain of the gain adjusting unit 21 is set by the gain setting unit 22 based on the saturation level detected by the saturation level detecting unit 23 so that the receiver 100 operates within the saturation level.

Here, the receiver is required to realize stable signal processing for each environment (place, time, application, etc.) in which the receiver is used. However, if the parameters used for AGC processing are fixed, the signal amplitude adjustment by AGC may be insufficient depending on the environment in which the receiver is used, and stable signal processing may not be realized.

Therefore, in the receiver 100 according to the first embodiment, a parameter setting unit 24 for setting parameters used for AGC processing based on an input signal is provided. Specifically, the parameter setting unit 24 receives the digital signal (input signal) output from the A / D converter 10, and sets the parameter used for detecting the saturation level in the saturation level detection unit 23 to the amplitude level of the input signal. Set based on. More specifically, the parameter setting unit 24 sets the number of stages of the moving average filter for calculating the moving average value of the input signal in the saturation level detection unit 23 based on the amplitude level of the input signal. As a result, the saturation level can be appropriately detected according to the amplitude fluctuation characteristic of the received signal, and stable signal processing can be performed regardless of the environment in which the receiver is used. Hereinafter, the parameter setting unit 24 and the saturation level detection unit 23 will be described in detail.

FIG. 2 is a block diagram showing the configuration of the parameter setting unit 24 shown in FIG. With reference to FIG. 2, the parameter setting unit 24 includes an amplitude determination unit 50, a counter 52, and a selector 54.

The amplitude determination unit 50 receives the digital signal (input signal) output from the A / D converter 10 and determines whether or not the amplitude level of the input signal exceeds the threshold value Da. The threshold value Da is appropriately preset to a level at which sudden fluctuations in the amplitude of the input signal due to disturbance or the like can be distinguished. This determination is performed in synchronization with the sampling of the A / D converter 10. Then, the amplitude determination unit 50 outputs the determination result to the counter 52.

The counter 52 counts the number of times the amplitude level of the input signal exceeds the threshold value Da based on the determination result of the amplitude determination unit 50. The counter 52 can detect the length of time that the amplitude level of the input signal exceeds the threshold value Da, and the larger the count value of the counter 52, the more the amplitude level of the input signal exceeds the threshold value Da. The longer the time spent and the smaller the count value, the shorter the time the amplitude level exceeds the threshold value Da.

The count by the counter 52 is performed up to the parameter update timing, and when the parameter is set in the saturation level detection unit 23 at the parameter update timing, the count value is reset to 0. The parameter update timing is generated, for example, every several samplings or a dozen or so samplings of the A / D converter 10. Then, the counter 52 outputs the count value (that is, the number of times the amplitude level of the input signal exceeds the threshold value) to the selector 54.

When the parameter update timing comes, the selector 54 selects one of the parameters Pa, Pb, ... Pn based on the count value from the counter 52 at that time, and sets the selected parameter in the saturation level detection unit 23. Output to. In the present embodiment, the parameters Pa, Pb, ... Pn specify the number of stages of the moving average filter used in the saturation level detection unit 23 to calculate the moving average of the input signal. The relationship between the count value by the counter 52 and the parameters Pa, Pb, ... Pn is associated in advance, and the selector 54 uses the relationship to select a parameter corresponding to the count value received from the counter 52. Output to the saturation level detection unit 23.

FIG. 3 is a timing chart showing an example of parameter setting by the parameter setting unit 24. With reference to FIG. 3, # i (i = 0, 1, 2, ...) Indicates the sampling timing in the A / D converter 10, and Tb indicates the interval of the parameter update timing. In this example, the parameter update timing occurs every five samplings, and when the time T0 is set to the initial time t = 0, the time T1 (t = Tb), the time T2 (t = 2Tb), and the time T3 (t). = 3Tb), at time T4 (t = 4Tb) ..., The parameter selected by the selector 54 based on the count value of the counter 52 is set in the saturation level detection unit 23.

In this example, in each section of time T0 to T1 and time T1 to T2, the amplitude level of the input signal is lower than the threshold value Da, so the counter output (count value of the counter 52) is "0". Therefore, in the section of the time T1 to T2 following the time T0 to T1 and the section of the time T2 to T3 following the time T1 to T2, the parameter of the saturation level detection unit 23 becomes the parameter Pa corresponding to the counter output "0". Set. In this example, the parameter Pa is also set as an initial value in the section from time T0 to T1.

In the section between times T2 and T3, the amplitude level of the input signal exceeds the threshold value Da at sampling timings # 12 and # 14, and the counter output at time T3 at the parameter update timing becomes “2”. Therefore, in the section from time T3 to T4 following time T2 to T3, the parameter of the saturation level detection unit 23 is set to the parameter Pb (Pb ≠ Pa) corresponding to the counter output “2”.

FIG. 4 is a block diagram showing the configuration of the saturation level detection unit 23 shown in FIG. With reference to FIG. 4, the saturation level detection unit 23 includes a moving average calculation unit 60 and a selector 70. The moving average calculation unit 60 includes a plurality of moving

average filters

62, 64, ... 66, and each moving

average filter

62, 64, ... 66 is a digital signal output from the A / D converter 10. (Input signal) is received.

The moving

average filters

62, 64, ... 66 have different numbers of stages for calculating the moving average value of the input signal. Specifically, the moving average filter 62 is a filter having the number of stages A (for example, 3 stages), and calculates and outputs the moving average value of the sampling data (amplitude level) for the most recent A times. The moving average filter 64 is a filter having the number of stages B (for example, 5 stages), and calculates and outputs the moving average value of the sampling data (amplitude level) for the most recent B times. The moving average filter 66 is a filter having the number of stages X (for example, n stages), and calculates and outputs the moving average value of the sampling data (amplitude level) for the latest X times.

The selector 70 receives the output of each moving

average filter

62, 64, ... 66 of the moving average calculation unit 60. Further, the selector 70 receives the parameter Pi (any of i = 1 to n) from the parameter setting unit 24. Then, the selector 70 selects the output of the moving average filter corresponding to the parameter Pi received from the parameter setting unit 24 according to the relationship of the parameter Pi and the moving

average filters

62, 64, ... 66 in advance. Output to the gain setting unit 22.

Regarding the correspondence between the parameters Pa, Pb, ... Pn and the moving

average filters

62, 64, ... 66, for example, the amplitude fluctuation of the received signal due to disturbance or the like is large, and the amplitude level of the input signal is the threshold value. If Da is frequently exceeded, a moving average filter with a large number of stages can be selected according to the parameters corresponding to the large count values so as to suppress excessive gain adjustment. On the other hand, when the amplitude fluctuation of the received signal is small, a moving average filter having a small number of stages can be selected according to the parameter corresponding to the small count value in order to improve the convergence of the gain adjustment. As a result, the moving average processing according to the amplitude fluctuation characteristic of the received signal can be realized, and the saturation level can be detected to realize stable signal processing.

FIG. 5 is a timing chart showing an example of detecting the saturation level by the saturation level detection unit 23. Also in FIG. 5, #i (i = 0, 1, 2, ...) Indicates the sampling timing in the A / D converter 10, and Tb indicates the interval of the parameter update timing.

With reference to FIG. 5, it is assumed that the parameter of the saturation level detection unit 23 is set to the parameter Pa in the section of the time T10 to T12 and the parameter Pb in the section of the time T12 to T14.

For example, when the moving average filter corresponding to the parameter Pa is a five-stage filter, for example, the saturation level at the sampling timing of # 4 is calculated based on the amplitude level of the input signals of # 0 to # 4, for example. The saturation level at the time of the sampling timing of # 5 is calculated based on the amplitude level of the input signals of # 1 to # 5.

Further, for example, when the moving average filter corresponding to the parameter Pb is a 7-stage filter, for example, the saturation level at the sampling timing of # 10 is calculated based on the amplitude level of the input signals of # 4 to # 10. NS.

As described above, in the receiver 100 according to the first embodiment, the saturation level (moving average value of the input signal) is calculated using the parameters set for each parameter update timing, and based on the calculated saturation level. The gain adjustment of AGC is performed. Therefore, it is possible to realize appropriate gain control according to the amplitude fluctuation characteristic of the received signal regardless of the environment in which the receiver 100 is used.

FIG. 6 is a diagram showing an example of the hardware configuration of the AGC circuit 20. With reference to FIG. 6, the AGC circuit 20 is composed of, for example, a DSP (Digital Signal Processor), and includes a CPU (Central Processing Unit) 26 and a memory (ROM (Read Only Memory) and RAM (Random Access Memory)) 27. , Including an input / output port 28 for inputting / outputting various signals. The CPU 26 expands the program stored in the ROM of the memory 27 into a RAM or the like and executes the program. The processing of the AGC circuit 20 is described in the program stored in the ROM.

FIG. 7 is a flowchart showing an example of a processing procedure executed in the AGC circuit 20. The series of processes shown in this flowchart are repeatedly executed at predetermined cycles (for example, sampling cycles).

With reference to FIG. 7, the AGC circuit 20 inputs a digital signal output from the A / D converter 10 (step S10). This signal input is executed every time the received signal is sampled in the A / D converter 10.

Next, the AGC circuit 20 determines whether or not the amplitude level of the input signal is larger than the threshold value Da (step S20). In the first embodiment, a preset value is used for the threshold value Da. When it is determined that the amplitude level of the input signal is larger than the threshold value Da (YES in step S20), the AGC circuit 20 adds the count value of the counter 52 (step S30). When it is determined that the amplitude level is equal to or less than the threshold value Da (NO in step S20), the counter 52 is not added.

Next, the AGC circuit 20 determines whether or not it is the parameter update timing (step S40). For example, as shown in FIGS. 3 and 5, the parameter update timing can be generated every 5 samplings in the A / D converter 10.

Then, when it is determined that it is the parameter update timing (YES in step S40), the AGC circuit 20 determines the parameter (number of stages of the moving average filter) used for detecting the saturation level based on the count value of the counter 52. Parameters) are set (step S50). When the parameter is set, the count value of the counter 52 is reset to 0 (step S60). If it is determined in step S40 that it is not the parameter update timing (NO in step S40), the processes of steps S50 and S60 are not executed and the process shifts to step S70.

Next, the AGC circuit 20 calculates the moving average of the input signal using the moving average filter corresponding to the parameter set in step S50 (step S70). More precisely according to the configuration shown in FIG. 4, the AGC circuit 20 selects the output of the moving average filter corresponding to the parameter set in step S50. The output of the moving average filter calculated (or selected) here corresponds to the detected value of the saturation level.

Then, the AGC circuit 20 sets the gain used for adjusting the amplitude level of the input signal based on the detected saturation level (step S80). Basically, the gain is set so that the higher the saturation level, the smaller the amplitude level after the amplitude adjustment, and the lower the saturation level, the larger the amplitude level after the amplitude adjustment. Then, the AGC circuit 20 adjusts the amplitude level of the input signal according to the set gain (step S90).

As described above, in the first embodiment, the parameter (number of stages of the moving average filter) used for detecting the saturation level of the digital signal based on the amplitude level of the digital signal output from the A / D converter 10. Is set. As a result, the saturation level can be detected according to the nature of the received signal regardless of the environment in which the receiver 100 is used. Therefore, according to the first embodiment, stable signal processing can be realized for each environment in which the receiver 100 is used.

Embodiment 2.
In the first embodiment, since the threshold value Da used in the amplitude determination unit 50 (FIG. 2) of the parameter setting unit 24 is a fixed value, for example, input signals exceeding the threshold value Da are continuous or threshold. In the case of a signal characteristic in which input signals lower than the value Da are continuous, the count value of the counter 52 becomes constant and the parameters are fixed. If the parameters are fixed, the gain adjustment may be stagnant in a situation where the gain adjustment has not progressed, such as immediately after the start of communication.

Therefore, in the second embodiment, the parameter is suppressed from being fixed by making the threshold value Da variable. Specifically, the threshold value Da is changed based on the count value of the counter 52. As a result, it is possible to prevent the gain adjustment from stagnation in a situation where the gain adjustment has not progressed, such as immediately after the start of communication.

In the first embodiment, assuming that the receiver is used in an environment with a large disturbance, the user measures the disturbance level of the received signal in advance before installing the receiver, and the measurement result is used. A procedure for setting the threshold value Da based on the above is required. In the second embodiment, since the threshold value Da is changed based on the count value of the counter 52, the above procedure by the user becomes unnecessary.

In the receiver 100 according to the second embodiment, the configuration of the parameter setting unit is different from that of the receiver of the first embodiment.

FIG. 8 is a diagram showing a configuration of a parameter setting unit according to the second embodiment. FIG. 8 corresponds to FIG. 2 described in the first embodiment. With reference to FIG. 8, the parameter setting unit 24A in the second embodiment further includes the threshold value setting unit 56 in the configuration of the parameter setting unit 24 in the first embodiment shown in FIG.

When the parameter update timing comes, the threshold value setting unit 56 sets the threshold value used in the amplitude determination unit 50 based on the count value of the counter 52. Specifically, the threshold value setting unit 56 sets the initial value of the threshold value to Da, raises the threshold value when the count value of the counter 52 is large, and raises the threshold value when the count value is small. reduce. That is, when the amplitude level of the input signal exceeds the threshold value for a long time (the count value of the counter 52 is large), the threshold value setting unit 56 increases the threshold value in the amplitude determination unit 50. When the amplitude level of the input signal exceeds the threshold value for a short time (count value is small), the threshold value in the amplitude determination unit 50 is reduced.

FIG. 9 is a timing chart showing an example when the threshold value of the amplitude determination unit 50 rises. Also in FIG. 9, #i (i = 0, 1, 2, ...) Indicates the sampling timing in the A / D converter 10, and Tb indicates the interval of the parameter update timing.

With reference to FIG. 9, the threshold value is the initial value Da in the section from time T20 to T21, and the input signal exceeds the threshold value Da at the sampling timings of # 0, # 1, # 2, and # 4. There is. Therefore, the counter output (count value of the counter 52) is relatively large, and the selector 54 outputs the parameter Pa corresponding to the counter output.

At the parameter update timing (time T21), the threshold value setting unit 56 raises the threshold value by X (X> 0) because the counter output is large (Da + X). As a result, in the section from time T21 to T22, the input signals exceeding the threshold value (Da + X) become # 6 and # 9, and the counter output (count value of the counter 52) decreases. Therefore, the selector 54 outputs the parameter Pb corresponding to this counter output. That is, in the section from time T20 to T21, the parameter Pa corresponding to the count value based on the threshold value Da is set, and in the section from time T21 to T22, the parameter Pb corresponding to the count value based on the threshold value (Da + X) is set. (Pb ≠ Pa) is set.

On the other hand, FIG. 10 is a timing chart showing an example in which the threshold value of the amplitude determination unit 50 decreases. Also in FIG. 10, #i (i = 0, 1, 2, ...) Indicates the sampling timing in the A / D converter 10, and Tb indicates the interval of the parameter update timing.

With reference to FIG. 10, the threshold value is the initial value Da in the section from time T30 to T31, and the input signal exceeds the threshold value Da at the sampling timings of # 2 and # 4. The counter 52 counts this number of times, and the selector 54 outputs the parameter Pc corresponding to the count value.

At the parameter update timing (time T31), the threshold value setting unit 56 determines that the counter output is relatively small, and lowers the threshold value by X (X> 0) (Da-X). As a result, in the section from time T31 to T32, the input signals exceeding the threshold value (Da-X) become # 5, # 7, and # 9, and the counter output increases. Therefore, the selector 54 outputs the parameter Pd corresponding to this counter output. That is, in the section from time T30 to T31, the parameter Pc corresponding to the count value based on the threshold value Da is set, and in the section from time T23 to T32, it corresponds to the count value based on the threshold value (Da-X). The parameter Pd (Pc ≠ Pd) is set.

As described above, in the second embodiment, the threshold value in the amplitude determination unit 50 is variable. If the threshold value is fixed, the parameter change based on the amplitude determination by the amplitude determination unit 50 may not function. For example, when the input signals exceeding the threshold value are continuous, the count value of the counter 52 becomes constant, and the parameters set in the saturation level detection unit 23 are fixed. Similarly, the parameters are fixed even when the input signals below the threshold value are continuous. Therefore, when the parameters are fixed, it is necessary for the user to measure the disturbance level of the received signal in advance before installing the receiver and set the threshold value based on the measurement result. ..

According to the second embodiment, since the threshold value is changed based on the count value of the counter 52, it is possible to suppress the parameter from being fixed even if the above input signals are continuous. can. Therefore, it is possible to suppress the stagnation of the gain adjustment in a situation where the gain adjustment has not progressed, such as immediately after the start of communication. Further, the user does not need to measure the disturbance level of the received signal in advance and set the threshold value based on the measurement result before installing the receiver.

Embodiment 3.
In the first embodiment, the parameters are set based on the count value of the counter 52 at the parameter update timing. In this case, regardless of whether the amplitude level of the input signal exceeds the threshold value continuously or intermittently, if the number of times the amplitude level exceeds the threshold value is the same in a predetermined period, The same parameters are set.

If the amplitude level intermittently exceeds the threshold value (hereinafter sometimes referred to as "intermittent saturation"), it is the stage where the amplitude adjustment is approaching convergence to some extent, and the parameter is changed. The need is not high. On the other hand, if the amplitude level continuously exceeds the threshold value immediately after the start of communication (hereinafter, may be referred to as "continuous saturation"), the amplitude adjustment has not progressed and the above-mentioned As such, it is necessary to change the parameters in order to prevent the parameters from being fixed and the gain adjustment from becoming stagnant.

In the second embodiment, the parameter fixation is suppressed by changing the threshold value based on the count value of the counter 52. In the third embodiment, a method different from that of the second embodiment is shown. That is, in the third embodiment, the number of consecutive updates of the count value of the counter 52 is counted, and the parameter is set based on the number of consecutive updates.

Whether or not continuous saturation has occurred can be detected by the number of consecutive updates of the count value of the counter 52. Then, when the number of continuous updates of the count value is large, that is, when continuous saturation occurs, the saturation level detection unit 23 sets the parameter so that the saturation level is detected by the moving average filter having a small number of stages. Therefore, the responsiveness of the gain adjustment can be improved. As a result, the amplitude adjustment can be completed at an early stage.

Even in the receiver 100 according to the third embodiment, the configuration of the parameter setting unit is different from that of the receiver of the first embodiment.

FIG. 11 is a diagram showing a configuration of a parameter setting unit according to the third embodiment. This FIG. 11 also corresponds to FIG. 2 described in the first embodiment.

With reference to FIG. 11, the parameter setting unit 24B in the third embodiment further includes the differential filter 58 in the configuration of the parameter setting unit 24 in the first embodiment shown in FIG. The differential filter 58 calculates the difference between the count values of the counter 52, and counts the number of consecutive times when the difference occurs. The count value by the differential filter 58 corresponds to the number of consecutive updates of the count value of the counter 52, that is, corresponds to the measured value of the time when the amplitude level of the input signal continuously exceeds the threshold value.

Note that the count by the differential filter 58 is also performed up to the parameter update timing as in the counter 52, and when the parameter is set in the saturation level detection unit 23 at the parameter update timing, the count value is reset to 0.

The differential filter 58 outputs a count value corresponding to the number of consecutive updates of the count value of the counter 52 to the selector 54. Then, in the third embodiment, the selector 54 selects one of the parameters Pa, Pb, ... Pn based on the count value received from the differential filter 58 at the parameter update timing, and is selected. The parameter is output to the saturation level detection unit 23.

FIG. 12 is a timing chart showing an example of parameter setting by the parameter setting unit 24B of the third embodiment. With reference to FIG. 12, in this example, when the parameter update timing occurs every 10 samplings and the time T40 is set to the initial time t = 0, the time T41 (t = Tb) and the time T42 (t =) At 2Tb), time T43 (t = 3Tb) ..., The parameter selected by the selector 54 is set in the saturation level detection unit 23.

In this example, in the section between times T40 and T41, the amplitude level of the input signal exceeds the threshold value Da at sampling timings # 1 and # 5 to # 9, and the counter output of the counter 52 at time T41 at the parameter update timing. (A9) becomes "6". In the section from time T41 to T42, the amplitude level of the input signal exceeds the threshold value Da at sampling timings # 10, # 12, # 14, # 16, # 17, and # 19, and at time T42 of the parameter update timing. The counter output (A19) of the counter 52 is also “6”. That is, when looking at the counter output of the counter 52, the same count value is obtained in the section from time T40 to T41 and the section from time T41 to T42.

On the other hand, looking at the output of the differential filter 58, in the section from time T40 to T41, the amplitude level of the input signal continuously exceeds the threshold value Da at sampling timings # 5 to # 9 (continuously for 5 sample periods). , It can be seen from the output of the differential filter 58 that continuous saturation occurs. Therefore, in the section from time T41 to T42, the parameter of the saturation level detection unit 23 is set to the parameter Pb based on the output of the differential filter 58.

In the section from time T41 to T42, the amplitude level of the input signal continuously exceeds the threshold value Da only during the two sample periods of sampling timings # 16 and # 17, and is intermittent from the output of the differential filter 58. It can be seen that saturation has occurred. Therefore, in the section from time T42 to T43, the parameter of the saturation level detection unit 23 is set to the parameter Pc (Pc ≠ Pb) based on the output of the differential filter 58.

In this example, in the first embodiment in which the differential filter 58 is not provided, the parameters in the section from time T41 to T42 are set based on the counter output (A9) of the counter 52 in the section from time T40 to T41, and the time is set. The parameters in the section from time T42 to T43 are set based on the counter output (A19) of the counter 52 in the section from T41 to T42. Therefore, the parameters are not updated.

On the other hand, in the third embodiment, the parameter in the section of time T41 to T42 is set to Pb based on the continuous output of the differential filter 58 in the section of time T40 to T41, and the time T41 to T42. Based on the intermittent output of the differential filter 58 in the interval, the parameter in the interval from time T42 to T43 is set to Pc.

As described above, according to the third embodiment, by providing the differential filter 58, it is possible to set parameters by distinguishing between continuous saturation and intermittent saturation. Then, when continuous saturation occurs, the parameter is set so that the saturation level detection unit 23 detects the saturation level with a moving average filter having a small number of stages. As a result, the responsiveness of the gain adjustment can be improved and the amplitude adjustment can be completed at an early stage.

Embodiment 4.
In each of the above embodiments, the parameter update timing is fixed (constant interval), but in the fourth embodiment, the parameter update timing is variable. Specifically, when the amplitude stabilizes after the gain adjustment converges, the parameter update frequency is reduced to suppress unnecessary parameter updates, and continuous saturation occurs immediately after the start of communication. In this situation, the convergence of gain adjustment can be improved by increasing the frequency of parameter updates.

FIG. 13 is a block diagram showing a configuration of a receiver according to the fourth embodiment. With reference to FIG. 13, the receiver 100A includes a receiving unit 30A and a demodulating unit 40. The receiving unit 30A includes an A / D converter 10 and an AGC circuit 20A. In the configuration of the AGC circuit 20 shown in FIG. 1, the AGC circuit 20A further includes a parameter update timing adjusting unit 25, and includes a parameter setting unit 24B instead of the parameter setting unit 24. The parameter setting unit 24B is as described with reference to FIG. 11 in the third embodiment.

The parameter update timing adjustment unit 25 adjusts the parameter setting timing (update timing) output from the parameter setting unit 24B to the saturation level detection unit 23. Specifically, the parameter update timing adjusting unit 25 lengthens the interval of the parameter update timing when intermittent saturation occurs, and continuous saturation occurs immediately after the start of communication or the like. In that case, the interval of parameter update timing is shortened.

FIG. 14 is a diagram showing the configuration of the parameter setting unit 24B and the parameter update timing adjustment unit 25 in the AGC circuit 20A shown in FIG. As described with reference to FIG. 14, the parameter setting unit 24B includes the differential filter 58. The differential filter 58 calculates the difference between the count values of the counter 52, and counts the number of consecutive times when the difference occurs.

The parameter update timing adjustment unit 25 includes a timing output counter 75. The timing output counter 75 increments the counter at a predetermined cycle, and when the count value exceeds the maximum increment number, outputs the parameter update timing to the parameter setting unit 24B. The timing output counter 75 resets the count value to 0 when the parameter update timing is output to the parameter setting unit 24B.

Here, the timing output counter 75 receives the count value by the differential filter 58, and changes the maximum increment number of the counter in the timing output counter 75 based on the count value. Specifically, when the count value of the differential filter 58 is small and intermittent saturation occurs, the timing output counter 75 raises the maximum increment number. As a result, the interval of the parameter update timing becomes long, and the parameter update frequency is suppressed.

On the other hand, when the count value of the differential filter 58 is large and continuous saturation occurs, the timing output counter 75 lowers the maximum increment number. As a result, the interval of the parameter update timing is shortened, and the frequency of parameter update is increased.

FIG. 15 is a timing chart showing an example of changing the parameter update timing. With reference to FIG. 15, in this example, the output of the differential filter 58 is intermittent (intermittent saturation) in the interval between times T50 and T51. Therefore, the maximum increment number of the timing output counter 75 is added by Nx1 to the initial value N. As a result, the interval of the parameter update timing is extended by the time Tn (Tb + Tn), and the next parameter update timing is extended from the time T52 to the time T53.

The output of the differential filter 58 is intermittent even in the section from time T51 to T53. Therefore, the maximum increment number of the timing output counter 75 is added by Nx2 (Nx2> Nx1) to the initial value N. As a result, the interval of the parameter update timing is longer than the initial time by 2 Tn (Tb + 2 Tn), and the next parameter update timing is extended to the time T55.

FIG. 16 is a diagram for explaining the effect of expanding the parameter update timing interval. FIG. 16 shows a waveform when the gain adjustment is converged and the amplitude of the signal is stable. The upper row shows the waveform when the parameter update timing is not changed as a reference example, and the lower row shows the waveform when the parameter update timing interval is extended by the receiver 100A according to the fourth embodiment. ing.

With reference to FIG. 16, in the upper reference example, since the parameter update timing is fixed (every 10 sample timings in this example), the time is set even though the gain adjustment is converged and the amplitude is stable. The parameters are updated unnecessarily at T61, T62, T63, ....

On the other hand, in the fourth embodiment of the lower stage, the parameter update timing interval is extended by adjusting the parameter update timing (30 sample timing in this example), and unnecessary parameter update is suppressed. There is.

FIG. 17 is a timing chart showing another example of changing the parameter update timing. With reference to FIG. 17, in this example, the continuous output of the differential filter 58 is seen in the interval from time T70 to T71 (continuous saturation). Therefore, the maximum increment number of the timing output counter 75 is subtracted by Nx1 with respect to the initial value N. As a result, the interval of the parameter update timing is shortened by the time Tn (Tb-Tn), and the next parameter update timing is changed from the time T73 to the time T72.

The continuous output of the differential filter 58 is also observed in the section from time T71 to T72. Therefore, the maximum increment number of the timing output counter 75 is subtracted by Nx2 (Nx2> Nx1) with respect to the initial value N. As a result, the interval of the parameter update timing is shortened by 2 Tn (Tb-2Tn) from the initial time, and the next parameter update timing is changed to the time T74.

FIG. 18 is a diagram illustrating the effect of shortening the parameter update timing interval. FIG. 18 shows the waveform when the gain adjustment has not converged. The upper row shows the waveform when the parameter update timing is not changed as a reference example, and the lower row shows the waveform when the parameter update timing interval is shortened by the receiver 100A according to the fourth embodiment. ing.

With reference to FIG. 18, in the upper reference example, since the parameter update timing is fixed (every 20 sample timings in this example), the amplitude level of the input signal is a threshold value at sampling timings # 4 to # 9 and the like. The parameter setting that reflects that Da is continuously exceeded is after time T82. Therefore, the convergence of the gain adjustment is prolonged.

On the other hand, in the fourth embodiment of the lower stage, the parameter update timing interval is shortened by adjusting the parameter update timing (every 10 sample timings in this example), and the amplitude level of the input signal is set at time T81. A parameter is set that reflects that the threshold value Da is continuously exceeded. Therefore, the gain adjustment converges early.

As described above, in the fourth embodiment, the parameter update timing is variable. Then, when the amplitude is stable after the gain adjustment and convergence, it is possible to suppress the parameter update from being unnecessarily performed by reducing the parameter update frequency. On the other hand, in a situation where continuous saturation occurs immediately after the start of communication or the like, the convergence of gain adjustment can be improved by increasing the frequency of parameter updates.

Note that, in the above-described fourth embodiment, the values Nx1, Nx2, ... That define the change speed of the parameter update timing may be different values depending on whether the parameter update timing interval is expanded or shortened. For example, the value for shortening the parameter update timing interval may be larger than the value for increasing the interval. Thereby, the convergence of the gain adjustment can be effectively improved.

It is also planned that the embodiments disclosed this time will be appropriately combined and implemented within a technically consistent range. And it should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The technical scope indicated by the present disclosure is indicated by the scope of claims rather than the description of the embodiment described above, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims. ..

10 A / D converter, 20, 20A AGC circuit, 21 gain adjustment unit, 22 gain setting unit, 23 saturation level detection unit, 24, 24A, 24B parameter setting unit, 25 parameter update timing adjustment unit, 26 CPU, 27 memory , 28 I / O port, 30, 30A receiver, 40 demodulation unit, 50 amplitude determination unit, 52 counter, 54, 70 selector, 56 threshold setting unit, 58 differential filter, 60 moving average calculation unit, 62, 64, 66 moving average filter, 75 timing output counter, 100, 100A receiver.

Claims

An A / D converter that converts the received signal into a digital signal,
It is equipped with an automatic gain control circuit that adjusts the amplitude level of the digital signal.
The automatic gain control circuit
A saturation level detector that detects the saturation level of the digital signal output from the A / D converter, and
A gain setting unit that sets a gain used for adjusting the amplitude level based on the saturation level detected by the saturation level detection unit, and a gain setting unit.
A gain adjusting unit that adjusts the amplitude level according to the gain set by the gain setting unit, and a gain adjusting unit.
A receiver including a parameter setting unit that sets parameters used in the saturation level detection unit based on the amplitude level of the digital signal output from the A / D converter.
The saturation level detection unit includes a moving average filter that outputs the moving average of the digital signal output from the A / D converter as the saturation level.
The receiver according to claim 1, wherein the parameter is the number of stages of the moving average filter.
The reception according to claim 1 or 2, wherein the parameter setting unit sets the parameter according to the length of time during which the amplitude level of the digital signal output from the A / D converter exceeds the threshold value. Machine.
The receiver according to claim 3, wherein the parameter setting unit further changes the threshold value according to the length of time during which the amplitude level exceeds the threshold value.
The receiver according to claim 4, wherein the parameter setting unit increases the threshold value when the amplitude level exceeds the threshold value for a long time as compared with the case where the time is short.
The receiver according to claim 4, wherein the parameter setting unit makes the threshold value smaller when the time when the amplitude level exceeds the threshold value is short than when the time is long.
The receiver according to claim 3, wherein the parameter setting unit sets the parameters according to the length of time during which the amplitude level continuously exceeds the threshold value.
The parameter setting unit further includes an update timing adjusting unit for adjusting the update timing of the parameter set in the saturation level detecting unit.
The receiver according to claim 7, wherein the update timing adjusting unit adjusts the update timing according to the length of time during which the amplitude level continuously exceeds the threshold value.
The update timing adjusting unit according to claim 8, wherein when the time when the amplitude level continuously exceeds the threshold value is short, the interval between the update timings is longer than when the time is long. Receiving machine.
The update timing adjusting unit according to claim 8, wherein when the amplitude level continuously exceeds the threshold value for a long time, the update timing interval is shorter than when the time is short. Receiving machine.
It is an automatic gain control method for the receiver.
A step of detecting the saturation level of the digital signal output from the A / D converter that converts the received signal into a digital signal, and
A step of setting parameters used for detecting the saturation level based on the amplitude level of the digital signal output from the A / D converter, and a step of setting the parameters used for detecting the saturation level.
A step of setting the gain used for adjusting the amplitude level of the digital signal based on the detected saturation level, and
An automatic gain control method comprising the step of adjusting the amplitude level according to the set gain.
The step of detecting the saturation level includes a step of calculating the moving average of the digital signal output from the A / D converter and outputting it as the saturation level.
The automatic gain control method according to claim 11, wherein the parameter is the number of stages of the moving average.
The step of setting the parameters is
A step of determining whether or not the amplitude level of the digital signal output from the A / D converter exceeds the threshold value, and
The automatic gain control method according to claim 11, further comprising the step of setting the parameter according to the length of time that the amplitude level exceeds the threshold value.