JP3240458B2 - Automatic gain control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an automatic gain control device.

[0002]

2. Description of the Related Art A conventional automatic gain control device, for example, amplifies an input signal by a variable gain amplifier 1 and an output signal of the variable gain amplifier 1 by a multiplier 2 as shown in FIG. The output of the amplifier 2 is used as the output of the automatic gain control device, and the control voltage is supplied to the control voltage generation circuit 100 to generate a control voltage for controlling the output level of the automatic gain control device to a desired range. The signal is supplied to a gain amplifier 1 to control the gain, and a value based on the control voltage is supplied to a multiplier 2 as a multiplier to multiply the output signal of the variable gain amplifier by a multiplier to substantially amplify the output signal. Signal (A
GC output signal).

As a conventional automatic gain control device, for example, as shown in FIG. 11, an input signal is amplified by a multiplier 21 and an output signal of the multiplier 2 is supplied to a filter 22 to perform a filtering process. Multiplier 21 via 22
Is amplified by the multiplier 2, the output of the multiplier 2 is used as the AGC output signal, and the control voltage generation circuit 10
0 to generate a control voltage for controlling the level of the AGC output signal within a desired range, and supply the multiplier 21 with a value based on the control voltage as a multiplier to multiply the input signal by a multiplier to convert the input signal. AGC is substantially amplified, and a value based on the control voltage is supplied to the multiplier 2 as a multiplier, and the output signal of the multiplier 21 via the filter 22 is multiplied by a multiplier to substantially amplify the signal.
Output signal.

The input signal is amplified by the variable gain amplifier 1 and the multiplier 2 in the above-mentioned first automatic gain control device, and the multiplier 2 is used in the second automatic gain control device.
1 and the multiplier 2 amplify the input signal, so that the total gain can be increased as compared with the case of one-stage amplification by the variable amplifier 1 or the multiplier 21, and the gain is insufficient even when the input signal level is small. This is convenient even when the input signal level fluctuates greatly.

[0005]

When using the first conventional automatic gain control device, the gain characteristic of the variable gain amplifier 1 with respect to the control voltage is not a linear characteristic, but the output characteristic of the multiplier 2 with respect to the control voltage, that is, the gain characteristic. The characteristic is usually a linear characteristic, and the overall characteristic of the gain with respect to the control voltage by the variable gain amplifier 1 and the multiplier 2 does not become linear. In contrast, the input / output characteristics of the control voltage generation circuit 100 are usually designed to be linear.

FIG. 12 shows a conventional first automatic gain control device.
When the time constant of the control voltage generation circuit 100 is large when the burst signal shown in FIG. 12A is input, the AGC output signal level is maintained over the first predetermined period when the burst signal is input as shown in FIG. Not within the desired range,
When the time constant of the control voltage generation circuit 100 is small, FIG.
As shown in (d), the AGC output signal level does not fall within the desired range due to partial oscillation during the period in which the burst signal is input, and the time constant of the control voltage generation circuit 100 falls within an appropriate range. Only within the desired range as shown in FIG. However, since the overall characteristic of the gain with respect to the control voltage is non-linear as described above, the appropriate range of the time constant is narrow, and the AGC output signal is distorted with respect to the input signal of the first conventional automatic gain control device. There was a problem that it became a waveform.

Further, it takes time to reduce the gain of the variable gain amplifier 1 which is controlled to the maximum when no input signal is present. In this case, even if the time constant is appropriate, the time constant is large. In this case, the AGC output signal waveform becomes the same as that in the case of FIG. 12B, and the AGC output signal waveform is distorted.

When an input signal is amplified by the multiplier 21 and the multiplier 2 as in the second conventional automatic gain control device, the overall characteristic of the control voltage versus the gain is linear.
However, since the filter 22 exists between the multiplier 21 and the multiplier 2, the signal propagation is delayed by the filter 22. Therefore, a time difference occurs between the input signal input to the second automatic gain control device and the control voltage generated by the control voltage generation circuit 100. Even when this time difference is large and extends over one cycle of the input signal, if the time constant of the control voltage generation circuit 100 is kept small,
When the burst signal shown in FIG.
As shown in (b), the output signal waveform of the multiplier 21 vibrates without entering the desired range. This oscillation is due to the fact that a value based on the control voltage as a multiplier is supplied to the multiplier 21 with a delay, and this is a distortion similar to a case where the time constant is too small.

The output signal of the multiplier 21 is input to the multiplier 2 with a delay of t0 due to the filter 22.
Therefore, the multiplier 2 receives and amplifies the output signal of the multiplier 21 of FIG. 13B with a delay, and the output signal of the multiplier 2, that is, the AGC output signal waveform is distorted as shown in FIG. 13C. It becomes a waveform. This distortion has a delay time of one cycle from immediately after the input of the burst signal until the control voltage generation circuit 100 detects the AGC output signal. During this time, the gain of the multiplier 21 is not changed and After a delay of one minute, the output signal of the multiplier 21 is input to the multiplier 2,
Since the control voltage generation circuit 100 detects the level of the AGC output signal, the AGC output signal level does not approach the desired range.

Due to the delay time of the filter 22, the AGC output signal becomes over-amplified or conversely under-amplified. As a result, there has been a problem that the AGC output signal exceeds the desired range or becomes a level smaller than the desired range, and the AGC output signal level does not converge to the desired range.

The present invention provides an automatic gain control device capable of obtaining an output signal with little distortion even if the control voltage-gain characteristic is non-linear or even if there is an element delaying signal propagation in the loop. The purpose is to:

[0012]

An automatic gain control device according to a first aspect of the present invention comprises a first variable gain amplifying means for amplifying an input signal and an output signal from the first variable gain amplifying means. second and third variable gain amplifying means, second
Rectifier for rectifying the output signal from the variable gain amplifying means (2)
Stage, first integrating means for integrating the output of the rectifying means, and
Computing means for subtracting the output of the integrating means from the reference value;
The output of the calculating means is integrated and the integrated output is used as the output control signal.
A second integrating means, based on the output control signal.
The output signal level from the second variable gain amplifying means is adjusted to a predetermined level.
A first control signal generating means for controlling the gains of the first and second variable gain amplifying means so as to set the first and second variable gain amplifying means; A second control signal generating means for receiving an output signal from the gain amplifying means as an input signal and transmitting an output control signal for controlling an output signal level from the third variable gain amplifying means to a predetermined level; One of the output control signal from the signal generation means and the output control signal from the second control signal generation means is selected, and a third variable as a signal for gain control is selected.
A first selecting means for transmitting to the gain amplifying means, a second selecting means for selecting and transmitting one of the output signals of the second and third variable gain amplifying means, and an output of the calculating means.
Determine whether the force level is equal to or greater than a predetermined threshold value.
Selection control means for controlling the first and second selection means in conjunction with each other based on another output .

According to the automatic gain control device according to claim 1 of the present invention, the input signal is amplified by the first variable gain amplifying means, the output signal from the first variable gain amplifying means and the second and third Is amplified by the variable gain amplifying means. The output signal from the second variable gain amplifier is rectified.
And the rectified output is integrated by the first integrating means.
The output is subtracted from the reference value, and the subtracted output is output from the second integrating means.
And the output control signal is integrated.
The output signal level from the second variable gain amplifying means based on
The gain of the first and second variable gain amplifying means is controlled by the first control signal generating means so as to bring the level to a predetermined level . On the other hand, the gain of the third variable gain amplifying means is controlled based on the control signal from the first or second control signal generating means selected by the first selecting means. When the output signal level of the second variable gain amplifying means is a predetermined level, the output signal from the second variable gain amplifying means is selected by the second selecting means, and the first control signal generating means is selected by the first selecting means. The gain of the third variable gain amplifying means is controlled based on the control signal from the control circuit.

When the level of the output signal from the second variable gain amplifying means changes from the predetermined level, the gain of the third variable gain amplifying means changes the second control signal supplied through the first selecting means. Controlled based on the control signal from the generating means, the output signal level from the third variable gain amplifying means is controlled to a predetermined level. That is, the first control signal generation
The output from the arithmetic circuit in the generating means is equal to or greater than the threshold,
During the first selection under the control of the selection control means.
The control signal to the third variable gain amplifying means is changed by the selecting means.
Switching to the control signal from the second control signal generating means.
The control signal generated by the second control signal generation means.
Of the third variable gain amplifying means whose gain is controlled by the signal
The output will be selected by the second selection means.

In this case, when the second control signal generating means is used,
The constant is set smaller than the time constant of the first control signal generation means.
Is fast and follows the input, and the third variable
The output from the gain amplifying means falls within a predetermined level range
Will be. If this change is not made,
The time constant of the control signal generator 1 is set to be large.
Therefore, the output signal level from the second variable gain amplifying means
When the first control signal generation means changes from a predetermined level,
Tracking of the control signal generated by the second variable gain
The output signal from the amplifying means will exceed a predetermined level.
You. In this state, the second variable gain amplifying means
Of the first control signal generating means.
When the output from the arithmetic circuit falls below a predetermined threshold, it falls below the threshold.
The first selection method under the control of the selection control means during the
The control signal to the third variable gain amplifying means is controlled by the first stage.
Is switched to the control signal from the control signal generating means of
The control signal generated by the first control signal generating means
Therefore, the output of the second variable gain amplifying means whose gain is controlled
Is selected by the second selecting means.

An automatic gain control device according to a second aspect of the present invention is the automatic gain control device according to the first aspect.
When the control signal from the second control signal generating means is selected by the selecting means in place of the control signal from the first control signal generating means, the control signal from the second control signal generating means is changed to the first control signal from the first control signal generating means. And a copy control unit that matches the control signal from the control signal generation unit.

According to the automatic gain control device of the present invention , the control signal from the second control signal generating means is changed by the first selecting means to the control signal from the first control signal generating means. Is selected by the first selection means because the control signal from the second control signal generation means is made to match the control signal from the first control signal generation means immediately before switching by the copy control means. Even if the control signal is switched from the control signal from the first control signal refining unit to the control signal from the second control signal generation unit, the fluctuation due to the switching of the output signal level from the automatic gain control device is suppressed and the switching is performed. Sometimes no distortion occurs.

An automatic gain control device according to a third aspect of the present invention is the automatic gain control device according to the first aspect.
And a signal processing unit that takes an output signal from the variable gain amplifying unit as an input signal, performs predetermined processing on the input signal, and uses the output signal as an input signal of the second and third variable gain amplifying units.
When the signal processing means is provided, a delay time occurs in signal propagation due to processing by the signal processing means, and the delay time causes a change in the output signal level from the second variable gain amplifying means. Since the output signal is switched to the output signal from the gain amplifying means, the fluctuation of the output signal level from the automatic gain control device is suppressed regardless of the delay time.

An automatic gain control device according to a fourth aspect of the present invention is the automatic gain control device according to the first aspect.
And the second variable gain amplifying means are first and second multipliers each having a multiplier based on a value based on a control signal from the first control signal generating means, and the third variable gain amplifying means is a first selection means. It is a third multiplier that uses a value based on a control signal transmitted through the means as a multiplier. 1st, 2nd
And a third variable gain amplifier means first, second and third
Is multiplied by the constant and the input signal, and a multiplied output is sent out. The multiplier operates similarly to the first, second, and third variable gain amplifying means.

An automatic gain control device according to a fifth aspect of the present invention is the automatic gain control device according to the first aspect,
The control signal generating means of
Rectifying means for rectifying the output signal, first integrating means for integrating the output of the rectifying means, calculating means for subtracting the output of the first integrating means from a reference value, and integrating output of the calculating means. and wherein the <br/> that example Bei and second integrating means to output control signals.

According to the automatic gain control device of the fifth aspect of the present invention, the second control signal generating means is provided with the third variable gain control means.
Rectifying means for rectifying the output signal from the gain and amplification means, first integrating means for integrating the output of the rectifying means, calculating means for subtracting the output of the first integrating means from a reference value, and output of the calculating means. When the control signal generating means includes a second integrating means for integrating and using the integrated output as a control signal, the control signal generating means includes a third variable gain amplifying means based on an output signal level from the third variable gain amplifying means. A control signal for controlling the output signal level to a predetermined level is sent from the second control signal generation means .

[0022]

An automatic gain control device according to a sixth aspect of the present invention is the automatic gain control device according to the fifth aspect, wherein
When the control signal from the second control signal generation means is selected by the selection means instead of the control signal from the first control signal generation means, the first control signal generation means
And copying means for copying the output of the integrating means to the first integrating means in the second control signal generating means, wherein the change in the output signal level of the automatic gain control device due to the switching is caused by the copying by the copying means. Is suppressed.

An automatic gain control device according to a seventh aspect of the present invention is the automatic gain control device according to the sixth aspect, wherein
The copying unit is configured to control the level of the control signal from the first control signal generating unit and the level of the control signal from the second control signal generating unit so that the control signal from the second control signal generating unit matches the control signal from the first control signal generating unit. The control signal from the second control signal generator is made to coincide with the control signal from the first control signal generator when the level of the control signal has a predetermined relationship.

An automatic gain control device according to claim 8 of the present invention comprises: first variable gain amplifying means for amplifying an input signal;
A second amplifying output signal from the first variable gain amplifying means;
And a third variable gain amplifying means, and a second variable gain amplifying means for setting an output signal level from the second variable gain amplifying means to a predetermined level.
Control signal generating means for controlling the gains of the first and second variable gain amplifying means based on an output signal from the variable gain amplifying means as an input signal, and a first control signal generating means And an output control signal for controlling the output signal level from the third variable gain amplifying means to a predetermined level using the output signal from the third variable gain amplifying means as an input signal. The second control signal generation means to be transmitted and the output from the first control signal generation means
Force control signal and output control signal from the second control signal generating means.
And the third signal as a signal for gain control.
First selecting means for sending to the variable gain amplifying means;
Of each output signal of the third and third variable gain amplifying means.
A second selecting means for selecting and transmitting the first control signal, and a copying means for matching a control signal from the second control signal generating means with a control signal from the first control signal generating means. When the level of the control signal from the signal generation unit and the level of the control signal from the second control signal generation unit have a predetermined relationship, the control signal from the second control signal generation unit is changed to the first control signal. The control signal from the generation means .
(3) an output signal from the variable gain amplifying means as the first selecting means
Automatic gain control by selecting with the second selecting means linked with
It is transmitted as a control signal output .

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the automatic gain control circuit according to the present invention will be described. FIG. 1 is a block diagram showing a first embodiment of the automatic gain control circuit according to the present invention.

In the first embodiment of the automatic gain control circuit according to the present invention shown in FIG. 1, an input signal is supplied to a variable gain amplifier 1 for amplification, and an output signal of the variable gain amplifier 1 is applied to multipliers 2 and 3 And multiplies it by a multiplier described later, and outputs the output signals of the multipliers 2 and 3 as AGC output signals. The AGC output signal output from the multiplier 2 is supplied to a control voltage generation circuit 4 to detect the signal level of the AGC output signal, generate a control voltage (first control voltage) based on the detected signal level, and vary the control voltage. The signal is supplied to the gain amplifier 1 as a gain control signal, and the value based on the first control voltage is supplied to the multiplier 2 as a multiplier (hereinafter, the value based on the control voltage is simply referred to as a multiplier). , So that the AGC output voltage output from the multiplier 2 becomes a constant level.

Similarly, the AGC output signal output from the multiplier 3 is supplied to the control voltage generation circuit 5 to detect the signal level of the AGC output signal, and the control voltage (second control voltage) based on the detected signal level is detected. ), And one of the first control voltage and the second control voltage is supplied to the multiplier 3 as a multiplier via the switch circuit 7, and the AGC output voltage output from the multiplier 3 becomes a constant level. Control.
One of the AGC output signal output from the multiplier 2 and the AGC output signal output from the multiplier 3 is selected and transmitted through a switch circuit 8 which is switched in conjunction with a switch circuit 7.

The control voltage generating circuit 4 includes a rectifying circuit 41 for rectifying the AGC output signal output from the multiplier 2, an integrating circuit 42 to which the output voltage of the rectifying circuit 41 is input, and a control circuit for converting the output voltage of the integrating circuit 42. Adder 43 for subtracting from the reference voltage
And an integration circuit 4 to which an output voltage from the adder 43 is input.
The output voltage of the integration circuit 44, that is, the first control voltage output from the control voltage generation circuit 4 is supplied to the variable gain amplifier 1 as a gain control voltage to control the gain of the variable gain amplifier 1, The signal is supplied to the multiplier 2 as a multiplier, and is multiplied by the output signal of the variable gain amplifier 1.

The control voltage generating circuit 5 includes a rectifying circuit 51 for rectifying the AGC output signal output from the multiplier 3, an integrating circuit 52 to which the output voltage of the rectifying circuit 51 is input, and a control circuit for converting the output voltage of the integrating circuit 52. Adder 53 for subtracting from the reference voltage
And an integrating circuit 5 to which an output voltage from the adder 53 is input.
4, the output voltage of the integration circuit 54, that is, the second control voltage and the first control voltage output from the control voltage generation circuit 5 are switched via the switch circuit 7 which is switched in conjunction with the switch circuit 8. Is supplied to the multiplier 3 as a multiplier, and is multiplied by the output signal of the variable gain amplifier 1.

The copy control circuit 9 receives the voltage of the integration capacitor 421 of the integration circuit 42 as an input,
1, a buffer amplifier 92 that receives the voltage of the integration capacitor 441 of the integration circuit 44 as an input, and a switch circuit 93 that transfers the electric charge of the integration capacitor 421 to the integration capacitor 521 of the integration circuit 52 via the buffer amplifier 91 and copies it. And a switch circuit 94 for transferring the electric charge of the integrating capacitor 441 to the integrating capacitor 521 via the buffer amplifier 92 and copying the electric charge. The electric charges are transferred by turning on the associated switch circuits 93 and 94.

When the output voltage of the adder 43, that is, the absolute value of the level of the input signal of the switching control circuit 6 is smaller than a predetermined threshold, the switching control circuit 6 switches the switching circuit 7 to the output of the control voltage generating circuit 4. Side and the multiplier 3
Supply a value based on the control voltage of
The switch circuit 8 is switched to the output side of the multiplier 2 to select and transmit the AGC output signal output from the multiplier 2. Hereinafter, for simplicity of description, threshold values for switching by the switching control circuit 6 will be described as positive and negative including zero, instead of magnitudes of absolute values.

Further, the switching control circuit 6 includes an adder 4
When the output voltage of the control voltage generator 3 is an input signal and the input signal level is negative, the switch circuit 7 is switched to the output side of the control voltage generator 5 to supply the multiplier 3 with a value based on the second control voltage as a multiplier. The switch circuit 8 is switched to the output side of the multiplier 3 to select and send out the AGC output signal output from the multiplier 3. Further, the control circuit 6 switches the multipliers 3 from the value based on the first control voltage to the value based on the second control voltage by the switch circuit 7 only for a predetermined period from the time when the switch circuits 93 and 94 are switched.
Is turned on to transfer the charges of the integration capacitors 421 and 441 to the integration capacitors 521 and 541, respectively, and copy them.

Here, the time constant of the control signal generation circuit 4 is A
The time constant is set so as not to cause oscillation in the GC output signal waveform and larger than the time constant of the control signal generation circuit 5. The time constant of the control voltage generation circuit 5 is smaller than the time constant of the control signal generation circuit 4,
Is set to a time constant at which the optimum response signal waveform can be obtained from

In the first embodiment configured as described above, when the input signal is not supplied to the automatic gain control device, the output voltage level of the adder 43 is increased and is positive, so that the switching reference The value is less than the threshold value, and the switching circuits 7 and 8 are in the state shown in FIG. 1 under the control of the switching control circuit 6.

In this state, when the burst signal shown in FIG. 2A is supplied to the AGC circuit as an input signal, the burst signal is amplified by the variable gain amplifier 1, and
The amplified output from variable gain amplifier 1 is substantially amplified by multipliers 2 and 3. In this case, the gain of the variable gain amplifier 1 is controlled by the first control voltage, the multiplier 2 is a multiplier based on the value based on the first control voltage, and the multiplier 3 is based on the first control voltage. The value is a multiplier, and the AGC output signal output from the multiplier 2 is supplied to the control voltage generation circuit 4 and the AGC output signal output from the multiplier 3
The GC output signal is supplied to the control voltage generation circuit 5, and the first
And a second control voltage are respectively generated.

However, because the time constant of the control voltage generation circuit 4 is large, the control by the first control voltage is insufficient to follow up, and the level of the output signal from the multiplier 2 is reduced as shown in FIG.
As shown in (b), there is a portion that is higher than the desired range voltage level. Here, the desired range voltage level is indicated by positive or negative because AG before being rectified by the rectifier circuit 41.
This is because it is shown corresponding to the C output signal. The desired range voltage level is a voltage corresponding to the reference voltage supplied to the adders 43 and 53, and indicates a range desired as the AGC output voltage level.

On the other hand, since the time constant of the control voltage generation circuit 5 is set smaller than the time constant of the control voltage generation circuit 4, the following is sufficiently fast and the value based on the second control voltage is multiplied by the multiplier. The output signal from the multiplier 3 is output as an AGC output signal. Here, since the time constant of the control voltage generation circuit 5 is set to be small as described above, the AGC output signal output from the multiplier 3 is as shown in FIG. 2C, and the distortion is small.

However, the AGC output from the multiplier 2
The output signal is rectified in the rectifier circuit 41 and the rectifier circuit 4
The output voltage from 1 is integrated in the integration circuit 42, and the output voltage from the integration circuit 42 is subtracted from the reference voltage level in the adder 43. When the signal level of the output signal output from the multiplier 2 is increased, the output voltage level of the integration circuit 42 is increased, and the output voltage level of the adder 43 is sequentially reduced as shown in FIG. And becomes negative, and becomes equal to or greater than the threshold value as the switching reference value. As a result, under the control of the switching control circuit 6, the switching circuits 7 and 8 are switched from the state shown in FIG. 1 to the multiplier 3 to which the multiplier of the value based on the second control voltage is supplied. The output signal from the device 3 is sent out as an AGC output signal. Therefore, the AGC output signal level does not exceed the desired range voltage level.

On the other hand, during this time, the control loop formed by the variable gain amplifier 1, the multiplier 2, and the control voltage generation circuit 4 is continuously operating, and the first control loop output from the control voltage generation circuit 4 The output signal level output from the multiplier 2 which has received the value based on the control voltage as a multiplier gradually decreases over time, and decreases to the desired range voltage level. As a result, the output voltage level of the integrating circuit 42 is reduced, and the output voltage level of the adder 43 becomes less than (zero) the threshold value as a switching reference value, and under the control of the switching control circuit 6, the switching circuit 7 and 8 are switched to the state shown in FIG. 1, the output signal from the multiplier 2 is selected instead of the output signal from the multiplier 3, and the multiplier 3
Is switched from a value based on the second control voltage to a value based on the first control voltage.

That is, the gain control by the control voltage generation circuit 4 is performed by the automatic gain control device when the gains of the variable gain amplifier 1 and the multiplier 2 are controlled to be high when there is no input signal to the automatic gain control device. As the input signal is supplied, it takes time to reduce the gain and reduce the level of the AGC output signal from multiplier 2 to the desired range voltage level. Therefore, if the output signal of the multiplier 2 is set to the AGC output signal during this period, the period in which the AGC output signal exceeds the desired range voltage level becomes longer, and the large amplitude output signal is gradually attenuated. Output signal.

However, as described above, during the period t1 when the AGC output signal exceeds the desired range voltage level, the output signal of the multiplier 3 which has received the value based on the second control voltage as a multiplier is transmitted as the AGC output signal. Therefore, the AGC output signal level does not exceed the desired range voltage level, and after the period t1, the output signal of the multiplier 2 becomes the AGC output signal during the remaining period t2 in which the burst signal is continuously supplied. Will be sent as In this period t2, the output of the multiplier 2 does not exceed the desired range voltage level, and the AGC output signal becomes as shown in FIG.

Next, when the input signal of the automatic gain control device disappears, the output voltage level from the integrating circuit 42 decreases, and the output voltage level from the adder 43 sequentially increases and becomes positive. Therefore, under the control of the switching control circuit 6, the switching circuits 7 and 8 remain in the state shown in FIG.

As a result, the state returns to the state before the burst signal is applied, and the same operation is performed when the burst signal is next applied.

When it is necessary to quickly increase the gain after the burst signal disappears and follow a low-level signal, the threshold value as the switching reference value of the switching control circuit 6 is set by the adder 43. When the absolute value of the output voltage level is equal to or greater than a predetermined threshold value, the signal level of the AGC output signal output from the multiplier 2 increases, and the output voltage level of the adder 43 becomes higher than the threshold value. Is exceeded, the second control voltage is increased by the multiplier 3
, And the AGC output signal output from the multiplier 3 is selected by the switch circuit 8.
Switching can be performed when the signal level of the AGC output signal output from the multiplier 2 increases or decreases.

Even if it is necessary to increase the gain immediately after the burst signal disappears, if it is not necessary to quickly lower the gain and follow up when the level of the input signal of the AGC circuit increases, the switching is performed. The threshold value as the switching reference value of the control circuit 6 is made valid only when the output signal level from the adder 43 is on the positive side except zero, and the signal level of the AGC output signal output from the multiplier 2 is set. Decreases, and the output voltage level from the adder 43 exceeds a threshold value as a switching reference value, the second control voltage is used as a multiplier for the multiplier 3, and the AGC output output from the multiplier 3 is output. The signal may be selected by the switch circuit 8 so that the switching is performed only when the signal level of the AGC output signal output from the multiplier 2 decreases. .

2 (e) shows the waveform of the output voltage of the adder 43, FIG. 2 (f) shows the waveform of the output voltage of the adder 53, and FIG. The switching timing at which the second control voltage is supplied to the multiplier 3 as a multiplier is shown.

In the above, since the gain by the variable gain amplifier 1 and the multiplier 2 and the gain by the variable gain amplifier 1 and the multiplier 3 are instantaneously switched, the first control output from the control voltage generation circuit 4 Voltage and control voltage generation circuit 5
If the first control voltage level is slightly different from the second control voltage level at the time of switching to the second control voltage output from the switch, switching noise occurs.

However, according to the first embodiment of the automatic gain control circuit according to the present invention, when the switch circuit 7 switches from the first control voltage to the second control voltage as a multiplier to the multiplier 3, a predetermined value is used. The period switch circuits 93 and 94 are turned on, the charge of the capacitor 421 is copied to the capacitor 521, and the charge of the capacitor 441 is copied to the capacitor 541. Therefore,
There is no difference between the first control voltage level and the second control voltage level at the time of switching, and generation of switching noise is prevented.

Next, a description will be given of a second embodiment of the automatic gain control circuit according to the present invention. FIG. 3 is a block diagram showing a second embodiment of the automatic gain control circuit according to the present invention.

In the second embodiment, the variable gain amplifier 1 is replaced by a multiplier 21, an output signal of the multiplier 21 is supplied to a filter 22, and an output of the multiplier 21 is filtered by the filter 22. Are supplied to the multipliers 2 and 3 through the signal output from the multiplier 21 via the. The other configuration is the same as the configuration of the first embodiment, the same portions are denoted by the same reference numerals, and description of overlapping portions will be omitted. Also in the second embodiment, the time constant of the control voltage generation circuit 4 is set to be larger than the time constant of the control voltage generation circuit 5.

The operation of the automatic gain control circuit according to the second embodiment will be described with reference to the waveform diagram shown in FIG. In the second embodiment, when the burst signal shown in FIG. 4A is applied as an input signal of the automatic gain control device, the output from the multiplier 21 becomes as shown in FIG. 4B. The output signal from the multiplier 21 has a delay time t0 due to the existence of the delay time t0 due to the filtering in the filter 22.
AGC which is input to multipliers 2 and 3 with a delay and output from multiplier 2 corresponding to FIGS. 2 (b) and 2 (c)
The output signal and the AGC output signal output from the multiplier 3 are as shown in FIGS. 4 (c) and 4 (d).

The output voltage level of the adder 43 is shown in FIG.
As shown in (e), an AGC output signal output from the multiplier 3 to which a value based on the second control voltage is supplied as a multiplier under the control of the switching control circuit 6 from the beginning of the application of the burst signal. Is selected by the switch circuit 8 and the AGC output signal output from the multiplier 2 is switched when the output voltage level of the adder 43 becomes less than the threshold value as the switching reference value, that is, in the latter half of the input burst signal. Selected by the circuit 8 and transmitted.

FIG. 4F shows the output voltage level of the adder 53, and FIG. 4G shows the switching timing at which the first and second control voltages are supplied to the multiplier 3 as multipliers. Note that the first control voltage is always supplied to the multiplier 21 and the multiplier 2 as a multiplier. In the case of the present embodiment, the AGC output signal can be controlled to a desired range voltage level regardless of the existence of a delay time with respect to the signal of the filter 22.

Next, a third embodiment of the automatic gain control circuit according to the present invention will be described. FIG. 5 is a block diagram showing a third embodiment of the automatic gain control circuit according to the present invention. This embodiment digitally processes the stage from the stage after the multiplier 21 of the second embodiment to the stage before the switch circuit 8. This is the form of the case.

In the third embodiment of the automatic gain control circuit according to the present invention shown in FIG. 5, an input signal of the AGC circuit is supplied to a multiplier 21 and multiplied by a multiplier. The signal is supplied to a D converter 23 and converted into a digital signal. The digital signal output from the A / D converter 23 is supplied to digital multipliers 2D and 3D and multiplied by a multiplier.
The output digital signal of the digital multiplier 2D is supplied to a digital control signal generation circuit 4D to generate a first digital control signal, and the output digital signal of the digital multiplier 3D is supplied to a digital control signal generation circuit 5D to generate a second digital control signal. To generate a digital control signal.

The first digital control signal is supplied to a digital multiplier 2D as a multiplier, and is also supplied to a D / A converter 26 to be converted into an analog signal and converted as a multiplier.
To supply. The first and second digital control signals are supplied to a switch circuit 7, one of which is selected and supplied as a multiplier to a digital multiplier 3D. One of the output digital signals of the digital multipliers 2D and 3D is selected by a switch circuit 8 which is switched in conjunction with the switch circuit 7,
/ A converter 25, and converts the analog signal into an analog signal.
Transmitted as C output signal.

As shown in FIG. 6, the digital control signal generation circuit 4D includes an absolute value conversion circuit 11 for converting the output of the multiplier 2D to an absolute value, and a coefficient multiplier for multiplying the output of the absolute value conversion circuit 11 by a coefficient. 12, an adder 13 to which the output of the coefficient multiplier 12 is supplied, a shift register 14 to which the output of the adder 13 is input, and multiplying the output of the shift register 14 by a coefficient and supplying the output to the adder 13 A coefficient multiplier 15 and an adder 16 for subtracting the output of the shift register 14 from the reference value
And a coefficient multiplier 17 for multiplying the output of the adder 16 by a coefficient
An adder 18 to which the output of the coefficient multiplier 17 is supplied;
The absolute value conversion circuit 11 substantially performs a rectification operation and corresponds to the rectification circuit 41. The shift register 19 supplies the output of the adder and outputs the output to the adder 18.
2, adder 13, shift register 14, coefficient multiplier 15
Corresponds to the integration circuit 42 by performing coefficient multiplication and integration,
The adder 16 corresponds to the adder 43, and the coefficient multiplier 17, the adder 18, and the shift register 19 perform an integral operation by performing coefficient multiplication and accumulation, and correspond to an integrating circuit 44. Therefore, the digital control signal generation circuit 4D corresponds to the control voltage generation circuit 4 and performs the same operation as that.

The digital control signal generation circuit 5D is configured similarly to the digital control signal generation circuit 4D, corresponds to the control voltage generation circuit 5, and performs the same operation as that. Here, it is set by setting the coefficient values of the coefficient multipliers 12, 15 and 17 corresponding to the time constants of the control voltage generation circuits 4 and 5.

The switching control circuit 6D receives the output of the adder 16, and switches the switch circuits 7 and 8 from the position shown in FIG. 5 when the output of the adder 16 reaches a predetermined value, that is, a threshold or more. When the value becomes smaller than the threshold value, the switch circuits 7 and 8 are switched to the positions shown in FIG. The copy control means 9D operates the shift register 14 when switching the switch circuits 7 and 8 from the position shown in FIG.
Is transferred to the corresponding shift register of the digital control signal generation circuit 5D.

According to the third embodiment, the same operation as in the second embodiment is performed. In this case, the multiplier 21, A
In a loop including the / D converter 23, the filter 24, the multiplier 2D, the digital control signal generation circuit 4D, and the D / A transformer 26, the time delay due to the sampling of the A / D converter 23 and the processing in the filter 24 are performed. The time delay in the loop is large due to the time delay and the time delay of the D / A transformer 26, and the waveform of the output signal of the multiplier 21 and the waveform of the output signal of the multiplier 2D with respect to the input of the burst signal in FIG. Are as shown in FIGS. 4B and 4C, respectively. However, in the loop including the multiplier 3D and the digital control signal generation circuit 5D, there is no delay element, and the waveform of the output signal from the multiplier 3D becomes as shown in FIG. 4D, and is added to FIG. As in the case of the second embodiment, an AGC output signal without distortion is obtained by switching based on the output from the device 16.

Next, a description will be given of a fourth embodiment of the automatic gain control circuit according to the present invention. FIG. 7 is a block diagram showing a fourth embodiment of the automatic gain control circuit according to the present invention. In this embodiment, a digital signal processing circuit is provided from the stage following the A / D converter 23 of the third embodiment to the switch circuit 8. This is a mode in the case of performing the processing.

In the fourth embodiment of the automatic gain control circuit according to the present invention shown in FIG. 7, the input signal of the automatic gain control circuit is supplied to a multiplier 21 to be multiplied by a multiplier.
1 is supplied to an A / D converter 23 to be converted into a digital signal. The digital signal output from the A / D converter 23 is supplied to a digital signal processing circuit 28 for signal processing.
The digital AGC output obtained by the signal processing is converted to a D / A converter 25.
To a D / A converter 26, which converts the multiplier obtained by the signal processing into a multiplier of the analog signal, and supplies the multiplier to the multiplier 21 for multiplication with the input signal. are the sea urchin configuration good that.

In the present embodiment, a distortion reduction instruction switch 29 for instructing distortion reduction is provided, and when distortion reduction instruction is given based on the instruction, distortion reduction is performed.
Digital signal processing circuit 2 when low distortion reduction processing is not performed
8 is reduced. When it is not necessary to instruct to reduce distortion, this is a case where the present invention is applied to an FM receiver. The distortion caused by the AGC circuit is amplitude distortion, and it is not necessary to reduce distortion in an FM receiver or the like in which frequency information and phase information are more important than amplitude information.

The operation of the fourth embodiment will be described with reference to the flowchart shown in FIG. In the operation of the digital signal processing circuit 28, the correspondence is shown using the same reference numerals as those in the configurations of FIGS. The value obtained by filtering the output X of the multiplier 21 is temporarily stored as Y (step S
1) The value Y is multiplied by the first control signal data (AGCV1), and the multiplied value is temporarily stored as M2 (step S2). The operation in step S2 corresponds to the operation of the multiplier 2D. Subsequent to step S2, the absolute value of the multiplied value M2 is calculated and temporarily stored as a value AM2 (step S3). The operation in step S3 corresponds to the operation of the absolute value conversion circuit 11.

Subsequent to step S3, the value AM2 is multiplied by the coefficient A, the numerical value (REG1) of the first shift register is multiplied by the coefficient B, and the result of the multiplication is added to obtain the value REG.
1 is temporarily stored (step S4). Step S
The operations from 1 to S4 correspond to the operations by the absolute value conversion circuit 11, the coefficient multiplier 12, the adder 13, the shift register 14, and the coefficient adder 15. Step S
Subsequent to 4, the value REG1 is subtracted from the reference value (REF), and the subtracted value is stored as the value R1 (Step S)
5). The operation in step S5 corresponds to the operation in the adder 16.

Subsequent to step S5, the value R1 is multiplied by the coefficient C1, and the multiplication result is added with the numerical value (AGCV1) of the second shift register.
Is stored once (step S6), and subsequent to step S6, the value AGCV1 is supplied to the D / A converter 26, converted into an analog signal, and supplied to the multiplier 21 as a multiplier (step S7). The operation in step S6 corresponds to the operation by the coefficient multiplier 17, the adder 18, and the shift register 19. Subsequent to step S7, it is checked whether or not the low distortion instruction has been issued by the low distortion instruction switch 29 (step S8). When it is determined that the low distortion instruction has not been issued, the value M is determined following step S8.
2 is supplied to the D / A converter 25 and sent out as an analog AGC output signal (step S9). S step 8
When step S9 is executed, the multiplier 3D
Is not switched.

If it is determined in step S8 that the low distortion instruction has been issued, the value R is set following step S8.
It is checked whether 1 is correct (step S10). When it is determined to be positive in step S10, the value AGCV1 is set to the value AGCV2 and is stored once after step S10 (step S11). Subsequent to step S11, the value REF is set as the value REG2 and temporarily stored (step S12), and then the value M2 is sent to the D / A converter 25 (step S9). Here, the operation in step S11 corresponds to transfer and copying of the value AGCV1 to the value AGCV2, and step S12 also corresponds to transfer and copying to the REG2.

[0069] If it is judged not positive in step S10, the value Y and the second control signal data (AG C V2) Subsequently to step S10 and is multiplied by the multiplication value M3
Is temporarily stored (step S13). Step S
The operation 13 corresponds to the operation of the multiplier 3D. Subsequent to step S13, the absolute value of the multiplied value M3 is calculated to obtain the value A
It is temporarily stored as M3 (step S14). The calculation from step S14 to step S17 corresponds to the calculation in the digital control voltage generation circuit 5D.

Subsequent to step S14, the coefficient AM is added to the value AM3.
Are multiplied by the coefficient (REG2) and the coefficient B, and the results of both multiplications are added and temporarily stored as a value REG2 (step S15). Subsequent to step S15, the value REG2 is subtracted from the reference value (REF), and the subtracted value is the value R2.
Is temporarily stored (step S16). Step S
Subsequent to 16, the value R2 is multiplied by the coefficient C2, the value (AGCV2) is added to the multiplication result, and the added value is temporarily stored as the value AGCV2 (step S17).

Subsequent to step S17, it is checked whether the value AGCV2 is larger than the value AGCV1 (step S18). If it is determined in step S18 that the value AGCV2 is larger than the value AGCV1, the process proceeds to step S18.
Following the step 18, the value AGCV1 is temporarily stored as the value AGCV2 (step S19). Subsequent to step S19, the value M3 is supplied to the D / A converter 25, converted into an analog signal, and transmitted as an AGC output signal (step S19).
20). In step 18, the value AGCV2 is set to the value AGC
If it is not determined that it is larger than V1, step S18
Then, step S20 is executed.

The above operation of the digital signal processing circuit 28 in the case where the step of step S8 is eliminated is described in the third embodiment.
The operation is the same as in the case of

Next, a description will be given of a modification of the fourth embodiment of the automatic gain control circuit according to the present invention. In the modified example of the fourth embodiment, as shown in the flowchart of FIG. 9, steps S8 to S12 are omitted from the flowchart of FIG.
3 is executed. By doing so, a case where a processing with a fixed multiplier to the multiplier 3D output from the digital control signal generating circuit 5 D in this modification.

[0074]

As described above, according to the automatic gain control device according to the present invention, distortion is produced even when the control voltage versus gain characteristic is non-linear and there is an element that delays signal propagation in the loop. A small output signal can be obtained.

[Brief description of the drawings]

FIG. 1 is a first embodiment of an automatic gain control device according to the present invention.
It is a block diagram showing a form.

FIG. 2 is a first embodiment of an automatic gain control device according to the present invention.
FIG. 4 is a waveform chart for explaining the operation of the embodiment.

FIG. 3 is a second embodiment of the automatic gain control device according to the present invention.
It is a block diagram showing a form.

FIG. 4 is a second embodiment of the automatic gain control device according to the present invention.
FIG. 4 is a waveform chart for explaining the operation of the embodiment.

FIG. 5 is a third embodiment of the automatic gain control device according to the present invention.
It is a block diagram showing a form.

FIG. 6 is a third embodiment of the automatic gain control device according to the present invention.
FIG. 4 is a block diagram of a digital control signal generation circuit according to the embodiment.

FIG. 7 is a fourth embodiment of the automatic gain control device according to the present invention.
It is a block diagram showing a form.

FIG. 8 is a fourth embodiment of the automatic gain control device according to the present invention.
It is a flowchart for explaining the operation of the embodiment.

FIG. 9 is a fourth embodiment of the automatic gain control device according to the present invention.
It is a flow chart for explaining operation in a modification of an embodiment.

FIG. 10 is a block diagram showing a configuration of a first conventional automatic gain control device.

FIG. 11 is a block diagram showing a configuration of a second conventional automatic gain control device.

12 is a waveform chart for explaining the operation of the conventional automatic gain control device shown in FIG.

FIG. 13 is a waveform chart for explaining the operation of the conventional automatic gain control device shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Variable gain amplifier 2, 3 and 21 Multiplier 4 and 5 Control voltage generation circuit 4, 8, and 16 Switch 6 and 6D Switching control circuit 7 and 8 Switch circuit 9 Copy control circuit 22 and 24 Filter 2D and 3D Digital multiplier 4D And 5D digital control signal generation circuit 23 A / D converter 25 and 26 D / A converter 28 digital signal processing circuit 29 low distortion instruction switch

Claims (8)

(57) [Claims] A first variable gain amplifying means for amplifying an input signal; and a second variable gain amplifying means for amplifying an output signal from the first variable gain amplifying means.
And third variable gain amplifying means, and rectification for rectifying an output signal from the second variable gain amplifying means
Means, first integrating means for integrating the output of the rectifying means,
Arithmetic means for subtracting the output of the first integrating means from the reference value
And the output of the arithmetic means is integrated and the integrated output is output control signal
And a second integrating means, based on the output control signal.
And the output signal level from the second variable gain amplifying means
A first control signal generating means for controlling the gains of the first and second variable gain amplifying means so as to have a constant level; and a third constant set to a time constant smaller than the time constant of the first control signal generating means. A second control signal generating means for receiving an output signal from the variable gain amplifying means as an input signal and transmitting an output control signal for controlling an output signal level from the third variable gain amplifying means to a predetermined level; A first selector for selecting one of the output control signal from the control signal generator and the output control signal from the second control signal generator and transmitting the selected signal to the third variable gain amplifier as a signal for gain control; And second selecting means for selecting and transmitting one of the output signals of the second and third variable gain amplifying means; and determining whether an output level of the calculating means is equal to or higher than a predetermined threshold value.
An automatic gain control device, comprising: selection control means for determining whether or not the first and second selection means are interlocked based on the determination output based on the determination output . 2. The automatic gain control device according to claim 1, wherein the first selection means selects a control signal from the second control signal generation means instead of the control signal from the first control signal generation means. The automatic gain control device further comprises copy control means for making the control signal from the second control signal generation means coincide with the control signal from the first control signal generation means immediately before. 3. An automatic gain control device according to claim 1, wherein an output signal from said first variable gain amplifying means is used as an input signal, and said input signal is subjected to a predetermined process to perform second and third variable gain amplifying. An automatic gain control device comprising signal processing means for inputting the signal to the means. 4. The automatic gain control device according to claim 1, wherein said first and second variable gain amplifying means have a multiplier based on a value based on a control signal from said first control signal generating means.
And a second multiplier, wherein the third variable gain amplifying means is a third multiplier having a multiplier based on a value based on a control signal transmitted through the first selecting means. Gain control device. 5. The automatic gain control device according to claim 1, wherein said second control signal generating means includes a third variable gain amplifier.
Rectifying means for rectifying the output signal from the stage, first integrating means for integrating the output of the rectifying means, calculating means for subtracting the output of the first integrating means from a reference value, and integrating the output of the calculating means. that example Bei and second integrating means for an output control signal the integrated output Te automatic gain control device according to claim. 6. The automatic gain control device according to claim 5, wherein the first selection means selects a control signal from the second control signal generation means instead of the control signal from the first control signal generation means. when automatic gain control device characterized by comprising a copying means for copying the output of the first integrating means in the first control signal generating means to the first integrating means in the second control signal generating means. 7. The automatic gain control device according to claim 6 , wherein said copy means is adapted to match a control signal from said second control signal generation means with said first control signal generation means .
The level of the control signal from the first control signal generator and the second
When the level of the control signal from the control signal generating means has a predetermined relationship, the control signal from the second control signal generating means is matched with the control signal from the first control signal generating means. Automatic gain control device. 8. A first variable gain amplifying means for amplifying an input signal, second and third variable gain amplifying means for amplifying an output signal from the first variable gain amplifying means, and a second variable gain. In order to set the output signal level from the amplifying means to a predetermined level, an output signal from the second variable gain amplifying means is used as an input signal and the gains of the first and second variable gain amplifying means are controlled based on the output control signal. The first control signal generation means and a time constant smaller than the time constant of the first control signal generation means, and an output signal from the third variable gain amplification means is used as an input signal, and the signal from the third variable gain amplification means is used as an input signal. A second control signal generating means for transmitting an output control signal for controlling an output signal level to a predetermined level; and a first control signal generating means.
Output control signals and outputs from the second control signal generating means.
Select one of the control signals as a signal for gain control
First selecting means for sending to third variable gain amplifying means;
Output signals of the second and third variable gain amplifying means
Second selecting means for selecting and transmitting one of the signals, and copying means for matching a control signal from the second control signal generating means with a control signal from the first control signal generating means,
The level of the control signal from the first control signal generator and the second
The level of the control signal from the control signal generating means so that match the control signal from the control signal from the second control signal generating means a first control signal generating means when a predetermined relationship, the third The output signal from the variable gain amplifying means
Automatically selected by the second selection means linked with the selection means
An automatic gain control device for transmitting as an output of a gain control signal .