JP7275383B2 - Receiver and automatic gain control method - Google Patents

Description

The present disclosure relates to receivers and automatic gain control methods.

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 makes up the receiver. is restricted. Therefore, in order to achieve a high dynamic range, automatic gain control (hereinafter referred to as "AGC (Automatic Gain Control)") is sometimes performed to adjust the signal level (amplitude) of the received signal.

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

In Japanese Unexamined Patent Application Publication 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 by comparing the two, the saturation of the variable gain amplifier is detected and the gain is set. A method has been disclosed (see Patent Document 1).

JP 2016-25561 A

A receiver equipped with an AGC circuit 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 (for example, preset fixed values), depending on the environment in which the receiver is used, the amplitude adjustment of the signal by AGC may be insufficient, resulting in stable Signal processing may not be possible.

The present disclosure has been made to solve such problems, 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 they are used. .

A 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 section, a gain setting section, a gain adjustment section, and a parameter setting section. The saturation level detector detects the saturation level of the digital signal output from the A/D converter. The gain setting section sets a gain used for adjusting the amplitude level of the digital signal based on the saturation level detected by the saturation level detecting section. The gain adjustment section adjusts the amplitude level of the digital signal according to the gain set by the gain setting section. The parameter setting section sets parameters used in the saturation level detection section based on the amplitude level of the digital signal output from the A/D converter.

Also, an automatic gain control method of the present disclosure is an automatic gain control method for a receiver, comprising the steps of detecting a saturation level of a digital signal output from an A/D converter that converts a received signal into a digital signal; setting a parameter used for detecting saturation level based on the amplitude level of the digital signal output from the A/D converter; and adjusting the amplitude level of the digital signal based on the detected saturation level. setting a gain; and 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. The saturation level can be detected according to the characteristics of the received signal regardless of the environment in which the 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.

2 is a block diagram showing the configuration of a receiver according to Embodiment 1 of the present disclosure; FIG. 2 is a block diagram showing the configuration of a parameter setting unit shown in FIG. 1; FIG. 4 is a timing chart showing an example of setting parameters; 2 is a block diagram showing the configuration of a saturation level detection unit shown in FIG. 1; FIG. 4 is a timing chart showing an example of saturation level detection; 3 is a diagram showing an example of a hardware configuration of an AGC circuit; FIG. 4 is a flow chart showing an example of a procedure of processing executed in an AGC circuit; FIG. 10 is a diagram showing the configuration of a parameter setting unit according to Embodiment 2; 4 is a timing chart showing an example when the threshold value of the amplitude determination unit is increased; 4 is a timing chart showing an example when the threshold value of the amplitude determination unit is lowered; FIG. 12 is a diagram showing the configuration of a parameter setting unit according to Embodiment 3; FIG. 11 is a timing chart showing an example of parameter setting by a parameter setting unit according to Embodiment 3; FIG. FIG. 12 is a block diagram showing the configuration of a receiver according to Embodiment 4; FIG. 14 is a diagram showing configurations of a parameter setting section and a parameter update timing adjustment section in the AGC circuit shown in FIG. 13; FIG. 9 is a timing chart showing an example of changing parameter update timing; FIG. 10 is a diagram for explaining the effect of extending the parameter update timing interval; 9 is a timing chart showing an example of changing parameter update timing; FIG. 10 is a diagram for explaining the effect of shortening the interval between parameter update timings;

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. A plurality of embodiments will be described below, but appropriate combinations of the configurations described in the respective embodiments have been planned since the filing of the application. The same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated.

Embodiment 1.
FIG. 1 is a block diagram showing the configuration of a receiver according to Embodiment 1 of the present disclosure. Referring to FIG. 1, receiver 100 includes receiver 30 and demodulator 40 . Receiving section 30 includes A/D converter 10 and AGC circuit 20 .

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

AGC circuit 20 includes gain adjustment section 21 , gain setting section 22 , saturation level detection section 23 , and parameter setting section 24 . Gain adjuster 21 receives the digital signal output from A/D converter 10 and adjusts the gain according to the gain (also referred to as “gain”, “amplification factor”, etc.) set by gain setter 22 . , to adjust the amplitude level of the received digital signal. Note that, hereinafter, 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 adjustment section 21 is output to the demodulation section 40 .

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

The saturation level detector 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. In this 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 decreases when the amplitude level of the input signal is high so that the receiver operates within the saturation level. , excessive gain adjustments may be made. Therefore, in this 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 receiver 100 . Gain setting section 22 sets the gain of gain adjusting section 21 based on the saturation level detected by saturation level detecting section 23 so that 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, depending on the environment in which the receiver is used, there is a possibility that signal amplitude adjustment by AGC will be insufficient and stable signal processing cannot be achieved.

Therefore, receiver 100 according to the first embodiment is provided with parameter setting section 24 that sets parameters used for AGC processing based on an input signal. 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 section 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 detecting section 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 characteristics of the received signal, and stable signal processing can be performed regardless of the environment in which the receiver is used. The parameter setting unit 24 and saturation level detection unit 23 will be described in detail below.

FIG. 2 is a block diagram showing the configuration of the parameter setting section 24 shown in FIG. Referring to FIG. 2, parameter setting unit 24 includes an amplitude determining unit 50, a counter 52, and a selector .

The amplitude determination section 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 set in advance to a level capable of distinguishing, for example, sudden amplitude fluctuations of the input signal due to disturbance or the like. This determination is made in synchronization with the sampling of A/D converter 10 . Then, the amplitude determination section 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 section 50 . The length of time during which the amplitude level of the input signal exceeds the threshold value Da can be detected by the counter 52 . The longer the duration and the smaller the count value, the shorter the time during which the amplitude level exceeds the threshold value Da.

The counter 52 counts until the parameter update timing, and the count value is reset to 0 when the parameter is set to the saturation level detector 23 at the parameter update timing. The parameter update timing occurs, for example, every several times or ten-odd times of sampling in the A/D converter 10 . The counter 52 then 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, . Output to In the present embodiment, the parameters Pa, Pb, . A relationship between the count value of the counter 52 and the parameters Pa, Pb, . Output to saturation level detector 23 .

FIG. 3 is a timing chart showing an example of parameter setting by the parameter setting unit 24. As shown in FIG. Referring to FIG. 3, #i (i=0, 1, 2, . . . ) indicates the sampling timing in A/D converter 10, and Tb indicates the parameter update timing interval. In this example, parameter update timing occurs every five samplings, and when time T0 is set to initial time t=0, time T1 (t=Tb), time T2 (t=2Tb), time T3 (t =3Tb), at time T4 (t=4Tb) .

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

In the interval from time T2 to 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 of parameter update timing is "2". Therefore, in the interval from time T3 to T4 following time T2 to T3, the parameter of saturation level detector 23 is set to parameter Pb (Pb≠Pa) corresponding to counter output "2".

FIG. 4 is a block diagram showing the configuration of the saturation level detector 23 shown in FIG. Referring to FIG. 4 , saturation level detection portion 23 includes a moving average calculation portion 60 and a selector 70 . The moving average calculator 60 includes a plurality of moving average filters 62, 64, . . . 66, and each of the moving average filters 62, 64, . input signal).

The moving average filters 62, 64, . . . 66 differ from each other in the number of stages for calculating the moving average value of the input signal. Specifically, the moving average filter 62 is a filter with A stages (for example, three stages), and calculates and outputs a moving average value of sampling data (amplitude level) for the most recent A times. The moving average filter 64 is a filter with B stages (for example, 5 stages), and calculates and outputs a moving average value of sampling data (amplitude level) for the most recent B times. The moving average filter 66 is a filter with the number of stages X (for example, n stages), and calculates and outputs a moving average value of sampling data (amplitude level) for the most recent X times.

Selector 70 receives outputs of moving average filters 62 , 64 , . . . 66 of moving average calculating section 60 . The selector 70 also receives a parameter Pi (i=one of 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 pre-associated relationship between the parameter Pi and the moving average filters 62, 64, . . . 66. Output to gain setting section 22 .

With respect to the correspondence between the parameters Pa, Pb, . . . , and the moving average filters 62, 64, . If Da is frequently exceeded, a moving average filter with a large number of stages may be selected according to parameters corresponding to 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 with 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 gain adjustment. As a result, it is possible to realize moving average processing in accordance with the amplitude fluctuation characteristics of the received signal, and to detect the saturation level for realizing stable signal processing.

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

Referring to FIG. 5, it is assumed that the parameter of saturation level detector 23 is set to parameter Pa in the section from time T10 to T12, and set to parameter Pb in the section from time T12 to T14.

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

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

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

FIG. 6 is a diagram showing an example of the hardware configuration of the AGC circuit 20. As shown in FIG. Referring to FIG. 6, AGC circuit 20 is configured by, for example, a DSP (Digital Signal Processor), and includes a CPU (Central Processing Unit) 26, a memory (ROM (Read Only Memory) and RAM (Random Access Memory)) 27 and , and an input/output port 28 for inputting/outputting various signals. The CPU 26 develops a program stored in the ROM of the memory 27 in the RAM or the like and executes it. A program stored in the ROM describes the processing of the AGC circuit 20 .

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

Referring to FIG. 7, AGC circuit 20 receives the digital signal output from A/D converter 10 (step S10). This signal input is performed each time the A/D converter 10 samples the received signal.

Next, AGC circuit 20 determines whether or not the amplitude level of the input signal is greater than threshold value Da (step S20). In this Embodiment 1, a preset value is used for the threshold value Da. When it is determined that the amplitude level of the input signal is greater than threshold value Da (YES in step S20), AGC circuit 20 adds the count value of counter 52 (step S30). When it is determined that the amplitude level is equal to or lower than threshold value Da (NO in step S20), addition by counter 52 is not performed.

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

When it is determined that it is time to update the parameters (YES in step S40), the AGC circuit 20 determines the parameters used for saturation level detection (the number of stages of the moving average filter) based on the count value of the counter 52. parameters) are set (step S50). When the parameters are 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 process proceeds to step S70 without executing the processes of steps S50 and S60.

Next, the AGC circuit 20 calculates the moving average of the input signal using the moving average filter corresponding to the parameters set in step S50 (step S70). More precisely along the lines of the configuration shown in FIG. 4, the AGC circuit 20 selects the output of the moving average filter corresponding to the parameters set in step S50. The output of the moving average filter calculated (or selected) here corresponds to the detection 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 such that the higher the saturation level, the lower the amplitude level after amplitude adjustment, and the lower the saturation level, the higher the amplitude level after amplitude adjustment. The AGC circuit 20 then adjusts the amplitude level of the input signal according to the set gain (step S90).

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

Embodiment 2.
In Embodiment 1, the threshold value Da used in the amplitude determination unit 50 (FIG. 2) of the parameter setting unit 24 is a fixed value. If the signal characteristic is such that the input signal below the value Da continues, the count value of the counter 52 becomes constant and the parameter is fixed. If the parameters are fixed, there is a possibility that the gain adjustment will stagnate in situations such as immediately after the start of communication when the gain adjustment is not progressing.

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, delays in gain adjustment are suppressed when gain adjustment is not progressing, such as immediately after the start of communication.

In the first embodiment, assuming that the receiver is used in an environment with a large amount of disturbance, the user measures the disturbance level of the received signal in advance before installing the receiver, and the measurement result is Therefore, a procedure for setting the threshold value Da 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 is not necessary.

Receiver 100 according to the second embodiment differs from the receiver of the first embodiment in the configuration of the parameter setting section.

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

The threshold value setting section 56 sets the threshold value used in the amplitude determination section 50 based on the count value of the counter 52 when the parameter update timing comes. 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 for a long time (the count value of the counter 52 is large), the threshold setting section 56 increases the threshold in the amplitude determination section 50, When the amplitude level of the input signal exceeds the threshold for a short time (count value is small), the threshold in the amplitude determination section 50 is decreased.

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

Referring to FIG. 9, the threshold value is the initial value Da in the interval from time T20 to T21, and the input signal exceeds the threshold value Da at sampling timings #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 this counter output.

At the parameter update timing (time T21), the threshold value setting unit 56 increases the threshold value by X (X>0) (Da+X) because the counter output is large. As a result, the input signals exceeding the threshold value (Da+X) are #6 and #9 in the interval from time T21 to T22, and the counter output (the count value of the counter 52) decreases. Therefore, selector 54 outputs 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 when the threshold value of the amplitude determination section 50 is lowered. In FIG. 10 as well, #i (i=0, 1, 2, . . . ) indicates the sampling timing in the A/D converter 10, and Tb indicates the parameter update timing interval.

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

At the parameter update timing (time T31), the threshold setting unit 56 determines that the counter output is relatively small, and lowers the threshold by X (X>0) (Da-X). As a result, the input signals exceeding the threshold value (Da-X) are #5, #7, and #9 in the section from time T31 to T32, 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, the parameter Pc corresponding to the count value based on the threshold value (Da-X) is set. A parameter Pd (Pc≠Pd) is set.

As described above, in the second embodiment, the threshold in the amplitude determination section 50 is made variable. If the threshold is fixed, there is a possibility that the parameter change based on the amplitude determination by the amplitude determination section 50 will not work. For example, when the input signal exceeding the threshold continues, the count value of the counter 52 becomes constant and the parameter set in the saturation level detector 23 is fixed. Similarly, the parameter is also fixed when the input signal below the threshold continues. Therefore, if 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 based on the measurement results. .

According to the second embodiment, since the threshold value is changed based on the count value of the counter 52, even if the above input signals continue, it is possible to suppress the parameter from being fixed. can. Therefore, it is possible to suppress the stagnation of the gain adjustment in a situation such as immediately after the start of communication where the gain adjustment has not progressed. Further, the user does not need 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.

Embodiment 3.
In Embodiment 1, 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 during the predetermined period is the same, The same parameters are set.

If the amplitude level intermittently exceeds the threshold value (hereinafter sometimes referred to as "intermittent saturation"), it means that the amplitude adjustment is approaching convergence to some extent, and the parameter should be changed. Not very necessary. On the other hand, if the amplitude level continuously exceeds the threshold immediately after the start of communication (hereinafter sometimes referred to as "continuous saturation"), the amplitude adjustment is not progressing and the above , it is necessary to change the parameters in order to prevent the parameters from being fixed and the gain adjustment stagnating.

In the second embodiment, by changing the threshold value based on the count value of the counter 52, fixation of parameters is suppressed. This third embodiment shows a technique different from that of the second embodiment. 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 occurs can be detected from the number of consecutive updates of the count value of the counter 52 . Then, when the count value is continuously updated for a large number of times, that is, when saturation occurs continuously, parameters are set so that the saturation level is detected by a moving average filter with a small number of stages in the saturation level detection unit 23. Thereby, the responsiveness of gain adjustment can be improved. As a result, it becomes possible to complete the amplitude adjustment early.

Receiver 100 according to the third embodiment also differs from the receiver of the first embodiment in the configuration of the parameter setting section.

11 is a diagram showing a configuration of a parameter setting unit according to Embodiment 3. FIG. This FIG. 11 also corresponds to FIG. 2 described in the first embodiment.

Referring to FIG. 11, parameter setting unit 24B in the third embodiment further includes a differential filter 58 in the configuration of parameter setting unit 24 in the first embodiment shown in FIG. A 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 obtained by the differential filter 58 corresponds to the number of consecutive updates of the count value of the counter 52, that is, the measured value of the time during which the amplitude level of the input signal continuously exceeds the threshold value.

Similar to the counter 52, the count by the differential filter 58 is performed until the parameter update timing, and the count value is reset to 0 when the parameter is set to the saturation level detector 23 at the parameter update timing.

Differential filter 58 outputs a count value corresponding to the number of consecutive updates of the count value of counter 52 to selector 54 . In the third embodiment, when the parameter update timing comes, the selector 54 selects one of the parameters Pa, Pb, . The parameters are output to the saturation level detection section 23 .

FIG. 12 is a timing chart showing an example of parameter setting by the parameter setting unit 24B of the third embodiment. Referring to FIG. 12, in this example, parameter update timing occurs every 10 samplings. 2Tb), at time T43 (t=3Tb) .

In this example, in the section from time T40 to 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 of the parameter update timing is (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 also becomes "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 in 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 five sampling periods). , the output of the differential filter 58 shows continuous saturation. Therefore, the parameter of the saturation level detector 23 is set to the parameter Pb based on the output of the differential filter 58 in the interval from time T41 to T42.

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 at sampling timings #16 and #17, and the output of the differential filter 58 intermittently It can be seen that saturation has occurred. Therefore, in the section from time T42 to T43, the parameter of the saturation level detector 23 is set to the parameter Pc (Pc≠Pb) based on the output of the differential filter 58. FIG.

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

In contrast, in the third embodiment, the parameter is set to Pb in the section from time T41 to T42 based on the continuous output of the differential filter 58 in the section from time T40 to T41, and the parameter in the section from time T41 to T42 is set to Pb. 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 while distinguishing between continuous saturation and intermittent saturation. Then, when saturation occurs continuously, parameters are set so that the saturation level is detected by a moving average filter with a small number of stages in the saturation level detection unit 23 . Thereby, it is possible to improve the responsiveness of the gain adjustment and complete the amplitude adjustment early.

Embodiment 4.
In each of the above embodiments, the parameter update timing is fixed (constant intervals), 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 update, and continuous saturation occurs immediately after the start of communication. In such a situation, the convergence of the gain adjustment can be improved by increasing the update frequency of the parameters.

13 is a block diagram showing the configuration of a receiver according to Embodiment 4. FIG. Referring to FIG. 13, this receiver 100A includes a receiving section 30A and a demodulating section 40. In FIG. Receiving section 30A includes A/D converter 10 and AGC circuit 20A. AGC circuit 20A further includes parameter update timing adjusting section 25 in the configuration of AGC circuit 20 shown in FIG. The parameter setting unit 24B is as described in FIG. 11 in the third embodiment.

The parameter update timing adjustment section 25 adjusts the setting timing (update timing) of the parameter output from the parameter setting section 24B to the saturation level detection section 23 . Specifically, when intermittent saturation occurs, the parameter update timing adjusting unit 25 lengthens the intervals between parameter update timings, and when continuous saturation occurs immediately after the start of communication. In this case, shorten the parameter update timing interval.

FIG. 14 is a diagram showing configurations of the parameter setting section 24B and the parameter update timing adjustment section 25 in the AGC circuit 20A shown in FIG. Referring to FIG. 14, parameter setting unit 24B includes differential filter 58 as described in FIG. A 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 section 25 includes a timing output counter 75 . The timing output counter 75 increments the counter at a predetermined cycle, and outputs parameter update timing to the parameter setting section 24B when the count value exceeds the maximum number of increments. The timing output counter 75 resets the count value to 0 when it outputs the parameter update timing to the parameter setting section 24B.

Here, the timing output counter 75 receives the count value from 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 increases the maximum increment number. As a result, the intervals between parameter update timings are lengthened, 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 reduces the maximum increment number. As a result, the intervals between parameter update timings are shortened, and the frequency of parameter updates is increased.

FIG. 15 is a timing chart showing an example of changing parameter update timing. Referring to FIG. 15, in this example, the output of differential filter 58 is intermittent (intermittent saturation) in the interval from time T50 to T51. Therefore, the maximum increment number of the timing output counter 75 is added to the initial value N by N×1. As a result, the parameter update timing interval is lengthened by time Tn (Tb+Tn), and the next parameter update timing is extended from time T52 to time T53.

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

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

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

On the other hand, in the fourth embodiment shown in the lower part, the interval between parameter update timings is extended (30 sample timings in this example) by adjusting the parameter update timing, and unnecessary parameter update is suppressed. there is

FIG. 17 is a timing chart showing another modification of parameter update timing. Referring to FIG. 17, in this example, a continuous output of differential filter 58 is seen (continuous saturation) in the interval from time T70 to T71. Therefore, the maximum increment number of the timing output counter 75 is subtracted from the initial value N by N×1. As a result, the parameter update timing interval is shortened by time Tn (Tb-Tn), and the next parameter update timing is changed from time T73 to time T72.

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

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

Referring 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 does not exceed the threshold value at sampling timings #4 to #9, etc. The parameter setting that reflects the fact that Da is continuously exceeded is after time T82. Therefore, the convergence of gain adjustment is prolonged.

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

As described above, in the fourth embodiment, parameter update timing is made variable. Then, when the amplitude is stabilized after the gain adjustment converges, unnecessary updating of the parameters can be suppressed by lowering the update frequency of the parameters. On the other hand, in situations where saturation occurs continuously immediately after the start of communication or the like, it is possible to improve the convergence of gain adjustment by increasing the update frequency of parameters.

In the fourth embodiment described above, the values Nx1, Nx2, . For example, the value for shortening the parameter update timing interval may be larger than the value for extending the interval. This can effectively improve the convergence of gain adjustment.

It is also planned that the embodiments disclosed this time will be combined as appropriate within a technically consistent range. And the embodiment disclosed this time should be considered as an illustration and not restrictive in all respects. The technical scope indicated by the present disclosure is indicated by the scope of claims rather than the description of the above-described embodiments, and is intended to include all modifications within the scope and meaning 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 input/output port, 30, 30A receiving section, 40 demodulating section, 50 amplitude determining section, 52 counter, 54, 70 selector, 56 threshold setting section, 58 differential filter, 60 moving average calculating section, 62, 64, 66 moving average filter, 75 counter for timing output, 100, 100A receiver.

Claims (11)

an A/D converter that converts a received signal into a digital signal;
and an automatic gain control circuit that adjusts the amplitude level of the digital signal,
The automatic gain control circuit comprises:
a saturation level detector that detects the saturation level of the digital signal output from the A/D converter;
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;
a gain adjustment unit that adjusts the amplitude level according to the gain set by the gain setting unit;
a parameter setting unit for setting 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 a moving average of the digital signal output from the A/D converter as the saturation level,
The receiver , wherein the parameter is the number of stages of the moving average filter. 2. The receiver according to claim 1 , wherein said parameter setting section sets said parameter according to the length of time during which the amplitude level of the digital signal output from said A/D converter exceeds a threshold value. 3. The receiver according to claim 2 , wherein said parameter setting section further changes said threshold according to how long said amplitude level exceeds said threshold. 4. The receiver according to claim 3 , wherein said parameter setting section increases said threshold when said amplitude level exceeds said threshold for a long time than when said time is short. 4. The receiver according to claim 3 , wherein said parameter setting section makes said threshold smaller when said amplitude level exceeds said threshold for a short time than when said time is long. 3. The receiver according to claim 2 , wherein said parameter setting section sets said parameter according to the length of time during which said amplitude level continuously exceeds said threshold value. The parameter setting unit further includes an update timing adjustment unit that adjusts update timing of the parameter set in the saturation level detection unit,
7. The receiver according to claim 6 , wherein said update timing adjustment section adjusts said update timing according to the length of time during which said amplitude level continuously exceeds said threshold value. 8. The update timing adjustment unit according to claim 7 , wherein when the amplitude level continuously exceeds the threshold for a short time, the update timing interval is made longer than when the time is long. Receiving machine. 8. The update timing adjustment unit according to claim 7 , wherein when the amplitude level continuously exceeds the threshold value for a long time, the update timing adjustment unit shortens the update timing interval more than when the time is short. Receiving machine. A receiver automatic gain control method comprising:
detecting a saturation level of a digital signal output from an A/D converter that converts a received signal into a digital signal;
setting a parameter used for detecting the saturation level based on the amplitude level of the digital signal output from the A/D converter;
setting a gain used to adjust the amplitude level of the digital signal based on the detected saturation level;
adjusting the amplitude level according to the gain set;
The step of detecting the saturation level includes calculating a moving average of the digital signal output from the A / D converter and outputting it as the saturation level,
The automatic gain control method, wherein the parameter is the number of stages of the moving average. The step of setting the parameters includes:
determining whether the amplitude level of the digital signal output from the A/D converter exceeds a threshold;
and setting the parameter according to how long the amplitude level exceeds the threshold .

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