JP2001156562A - Agc circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an AGC circuit that can suppress an output power jumping due to changeover between AGC off and AGC on. SOLUTION: A control means of the AGC circuit 10 is provided with a detection means 14 that outputs a detected voltage, a voltage control means 17 that adjusts the voltage to provide an output of an AGC setting voltage, a comparison means 15 that receives the detected voltage and the AGC setting voltage to provide a comparison voltage, and a changeover means that selects the comparison means or an MGC setting voltage and provides an output of the selected voltage as a control signal of a level adjustment means 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AG used for, for example, a transmitter or a relay of a television broadcast signal.
The present invention relates to a C circuit (automatic gain control circuit), and more particularly to an AGC circuit that suppresses a jump in output power when switching from AGC off (manual gain control loop) to AGC on (automatic gain control loop).

[0002]

2. Description of the Related Art Conventionally, an AGC circuit (automatic gain control circuit) has been used in a television broadcast signal transmitting apparatus or a relay apparatus in order to stabilize an output power level.

FIG. 4 shows a configuration of a conventional AGC circuit 100. The AGC circuit 100 includes an attenuator 110 for attenuating an input signal to a predetermined amount of attenuation, an amplifier 120 for performing signal amplification, and a distributor 1 for extracting a part of a signal.
30, a detector 140, a comparator 150, and a switch 160 for switching between an AGC circuit and an MGC circuit (manual gain control circuit).

Next, the operation of the AGC circuit 100 will be described. The signal input from the input terminal IN is supplied to the attenuator 11
It is attenuated by 0 and amplified by the amplifier 120. Then, the signal passing through the distributor 130 is output from the output terminal OUT.

On the other hand, the signal extracted and distributed by the distributor 130 is input to the detector 140. Detector 1
40 is a detection voltage Vd corresponding to the power of the input signal.
Is output.

The comparator 150 compares the detection voltage Vd input to one terminal with the AGC setting voltage Va input to the other terminal, and outputs the comparison voltage Vc to the switch 16.
Output to 0.

In the switch 160, the comparison voltage Vc is input to one terminal a (hereinafter, referred to as a “comparison voltage input terminal”), and the MGC set voltage Vm is applied to the other terminal b (hereinafter, “MG”).
C setting voltage input terminal ”). In this switch 160, the switch S
Is switched, and the switch S is connected to the comparison voltage input terminal a or the MGC setting voltage input terminal b. Then, the comparison voltage Vc or the MGC setting voltage Vm passes through the switch 160 and is input to the attenuator 110.

The AGC circuit 100 includes a switch 160
Is connected to the comparison voltage input terminal a, the AGC is ON (automatic gain control loop). When the switch S of the switch 160 is connected to the MGC setting voltage input terminal b, the AGC circuit 100 is in the AGC off (manual gain control loop).

The amount of attenuation of the attenuator 110 is controlled based on the input control signal (comparison voltage Vc or MGC set voltage Vm).

With this configuration, a part of the output signal can be extracted to perform gain control, and output power can be stabilized.

[0011]

However, the above-mentioned AGC
In the circuit 100, when the AGC is off, the output voltage of the comparator 150 is not reflected on the output power because the attenuator 110 is controlled by the MGC set voltage Vm. Therefore,
The comparison voltage Vc in the AGC-off state becomes a voltage of the maximum value or the minimum value of the voltage value that can be output from the comparator 150 according to the comparison result.

When AGC is switched from AGC off to AGC on when the comparison voltage Vc is at the maximum value or the minimum value, the attenuator 110 supplies the maximum or minimum value of the comparison voltage Vc.
Is input, and the amount of attenuation in the attenuator 110 becomes maximum or minimum.

As described above, the amount of attenuation in the attenuator 110 when the AGC is switched from the AGC off to the AGC on may be minimized depending on the comparison result of the comparator 150 when the AGC is off.

Therefore, in the above-mentioned AGC circuit 100, A
When switching from GC off to AGC on, the output power may jump.

To prevent the output power from jumping, there is a switching circuit described in Japanese Patent Publication No. 3-17243, for example. In this switching circuit, a voltage obtained by adding the detection voltage output from the detector and the voltage input from the terminal is input to the voltage comparison circuit, so that the voltage input to the amplifier becomes the minimum gain of the amplifier. It is to be a corresponding value.

However, in the above-described switching circuit, since the capacitance of the capacitor charged by the detection voltage and the voltage input from the terminal and the resistance value of the resistor are predetermined, the jump of the output power is suppressed. Time cannot be changed. Therefore, there is a problem that an appropriate process cannot be performed according to the situation.

Further, in the above-mentioned switching circuit, there is a problem that the circuit configuration becomes complicated because it is necessary to provide two switching circuits. Further, since the rise of the output power cannot be suppressed depending on the operation order of these two switching circuits, there is a problem that the rise of the output power may not be suppressed in the above-described switching circuit.

An object of the present invention is to solve the above-mentioned problem and to suppress a surge in output power caused by switching between AGC off and AGC on.

[0019]

In order to solve the above problems, in an AGC circuit, a control means includes a detection means for outputting a detection voltage, and a voltage control means for adjusting a voltage value and outputting an AGC set voltage. And a comparison means for receiving the detection voltage and the AGC set voltage and outputting a comparison voltage, and a switching means for switching between the comparison voltage and the MGC set voltage and outputting as a control signal for controlling the level adjustment means.

With the above configuration, the voltage value of the AGC set voltage can be adjusted while the AGC is off.

The voltage control means outputs the MGC setting voltage as a control signal by the switching means (A
When the comparison voltage is selected as the control signal (when the AGC is turned on) when the GC is off), the level adjustment means for inputting the comparison voltage has a large amount of attenuation so that the amount of attenuation is large.
The voltage value of the C setting voltage is set.

With the above configuration, the output power when the AGC is switched from the AGC off to the AGC on can be reduced, and the rise of the output power can be reliably suppressed.

The switching timing of the switching means is controlled by the voltage control means. The voltage control means switches the voltage used as the output control signal of the switching means from the MGC set voltage to the comparison voltage, and then switches the voltage to a predetermined value. AG output until
The voltage value of the C voltage is gradually changed.

[0024] With the above-described configuration, the time until the output value is adjusted to a predetermined value (or the amount of change in the voltage value) can be adjusted to provide a range of time for suppressing the rise of the output power. Thus, appropriate processing can be performed according to the state of the circuit.

Further, a linear compensation circuit for processing the input signal is provided, and the level adjusting means adjusts the level of the output signal of the linear compensation circuit.

With the above configuration, even when the output voltage of the linear compensation circuit changes due to adjustment of the compensation amount or the like, the output power can be kept constant. Can be adjusted to be constant. Further, even when the AGC is switched from the AGC on to the AGC off, it is possible to suppress an excessive input to a subsequent circuit or the like.

Further, the voltage control means sets the voltage value of the MGC set voltage and outputs the MGC set voltage.

With the above configuration, the output power when the AGC is off can be made variable, and when the AGC is on, the voltage value of the control signal after switching to the AGC off can be adjusted. And can be prepared.

Further, when the comparison means outputs the comparison voltage as a control signal by the switching means, the voltage control means takes in the comparison voltage and sets the voltage value of the MGC set voltage based on the voltage value of the comparison voltage. Things.

With the above-described configuration, the voltage value of the voltage used as the control signal when the AGC is turned off can be set based on the voltage value used as the control signal when the AGC is turned on. Therefore, even when the AGC is switched from the AGC on to the AGC off, the output power can be prevented from jumping.

Further, the voltage control means sets the voltage value of the MGC set voltage to substantially the same value as the voltage value of the fetched comparison voltage.

With the above configuration, even when the AGC is switched from the AGC on to the AGC off, the voltage value of the control signal input to the attenuation means before and after the switching is substantially the same. Therefore, it is possible to suppress the output power from rising.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG. FIG. 1 shows the configuration of an AGC circuit 10 of the present example. This AGC circuit 10
Represents an attenuator 11, an amplifier 12, a distributor 13, a detector 14, a comparator 15, a switch 16, a control circuit 17
And

The attenuator 11 and the amplifier 1 shown in FIG.
2, the distributor 13, the detector 14, the comparator 15, and the switch 16 are respectively the attenuator 110, the amplifier 120, the distributor 130, and the detector 14 shown in FIG.
0, the comparator 150, and the switch 160 have the same configuration and operation, and a detailed description thereof will be omitted.

In the following description, "AGC ON" means a state in which an automatic gain control loop is formed. In this example, the switch S of the switch 16 is connected to the comparison voltage input terminal a.
And the voltage used as the input control signal of the attenuator 11 is the comparison voltage Vc.

AGC off is a state in which a manual gain control loop is formed. In this example, the switch of the switch 16 is connected to the MGC setting voltage input terminal b, and the input control signal of the attenuator 11 is Is the MGC setting voltage V
It means the state of m.

The control circuit 17 outputs an AGC set voltage Va to one terminal of the comparator 15. Control circuit 17
Now, the state of the circuit 10 (for example, AGC ON, AGC
The voltage value of the AGC setting voltage Va is set according to the state of the AGC setting voltage Va (off, immediately after switching, etc.).

When the AGC is on, the control circuit 17 sets, for example, an AGC set voltage Va having a predetermined constant value. When the AGC is off, the control circuit 17 sets an AGC setting voltage Va having a voltage value such that the output power of the signal output from the output terminal OUT decreases when the AGC is turned on.

The voltage value of the AGC set voltage Va when the AGC is off may be set in advance based on the range of the assumed detection voltage Vd, or may be set based on the measured detection voltage Vd. May be changed and set as appropriate. Further, it may be determined based on another value such as the voltage value of the MGC setting voltage Vm.

In this example, the control circuit 17 uses the MGC
The voltage value of the set voltage Vm is set, and the MGC set voltage Vm is output to the MGC set voltage input terminal b of the switch 16. Note that the MGC setting voltage Vm may be configured to be externally input.

Further, the control circuit 17 provides the switch 16 with A
A GC switching signal C is output, and a switch S
(That is, switching between AGC on and AGC off). Note that the AGC switching signal C may be configured to be externally input.

Next, in the AGC circuit 10 of the present embodiment, the AG
The operation when C is off will be described. When AGC is off,
The switch S of the switch 16 is connected to the MGC setting voltage input terminal b under the control of the control circuit 17.

Therefore, the MGC setting voltage Vm of the voltage value output from the control circuit 17 controls the amount of attenuation of the attenuator 11 as a control signal. The voltage value of the MGC setting voltage Vm is set in the control circuit 17 by, for example, an operator.

Further, the control circuit 17 controls the AGC setting voltage V
a, when the state of the circuit 10 is switched to AGC ON (that is, when the input control signal of the attenuator 11 is switched from the MGC set voltage Vm to the comparison voltage Vc).
Then, a voltage value is set such that the output power output from the output terminal OUT decreases, and the voltage is output to the comparator 15.

Therefore, the AGC set voltage Va is equal to the attenuator 1
The voltage value is set so that the amount of attenuation of 1 is larger than when the AGC is off before switching. That is, for example, when the amount of attenuation in the attenuator 11 and the voltage serving as the control signal input to the attenuator 11 are in a proportional relationship, the comparison voltage Vc output from the comparator 15 is equal to the AGC set voltage Va. A voltage value that is higher than the MGC setting voltage Vm (that is, for example, when the AGC setting voltage Va is the reference voltage (plus side) of the comparator 15, the voltage value is higher than the assumed detection voltage Vd). Is set to

M input to the MGC setting voltage input terminal b
The GC set voltage Vm passes through the switch 16 and passes through the attenuator 11.
Is input to Then, in the attenuator 11, the input MG
The input signal from the input terminal IN is attenuated by the amount of attenuation based on the C setting voltage Vm.

As described above, when the AGC is off, the AG
The C circuit 10 is an MGC that is set and output by the control circuit 17.
Controlled by the set voltage Vm, the output power is kept constant.

Next, the AG in the AGC circuit 10 of the present embodiment will be described.
The operation when switching from C off to AGC on will be described.

When the AGC switch signal C output from the control circuit 11 is input to the switch 16 when the AGC circuit is off, the connection of the switch S of the switch 16 changes from the MGC setting voltage input terminal b to the comparison voltage input terminal. a, and the AGC is turned on.

When the switch S is switched by the switch 16, the voltage passing through the switch 16 becomes the MGC set voltage Vm
To the comparison voltage Vc.

In this case, the switched comparison voltage Vc
Is a voltage value based on the AGC setting voltage Va of the voltage value set by the control circuit 17 as described above,
It is output from the comparator 15.

Therefore, in the attenuator 11, when the input voltage is switched to the comparison voltage Vc, the amount of attenuation becomes larger than before the switching. Then, an output signal whose power is lower than before the switching passes through the distributor 13 and is output from the output terminal OUT.

In this example, the control circuit 17 determines that the AG
After switching to C-on, the AGC set voltage Va is gradually changed until it reaches a predetermined value. Then, the output power fluctuates gradually and approaches a predetermined value (power value output after switching).

When the AGC set voltage reaches a predetermined value, the AGC circuit 10 of this embodiment controls the amount of attenuation of the attenuator 11 so that the detection voltage Vd becomes constant. Is kept.

As described above, by providing the control circuit 17 for setting the voltage value of the AGC setting voltage Va when the AGC is in the off state, the output when the AGC is switched from the AGC off to the AGC on is provided. The power can be reduced, and the surge of the output power can be reliably suppressed.

Further, as described above, AGC is turned off from AGC off.
By providing the control circuit 17 for performing a process of gradually bringing the AGC set voltage Va closer to a predetermined value after switching to the GC-on state, the time until the predetermined value is reached (or a change in the voltage value) is obtained. By adjusting (amount), it is possible to provide a range of time for suppressing the rise of the output power, so that appropriate processing can be performed according to the state of the circuit.

Further, as described above, by providing the control circuit 17 for setting the voltage value of the MGC setting voltage Vm, it is possible to control the output power when the AGC is off.

In the above-described embodiment, the signal input to the input terminal IN is attenuated by the attenuator 11, but the linear compensation circuit is provided between the input terminal IN and the attenuator 11. It is good.

In this case, for example, as shown in FIG.
The C circuit 20 may have a configuration in which a linear compensation circuit 21 is provided in a stage preceding the attenuator 11 of the AGC circuit 10 described above.

With this configuration, the output power from the output terminal OUT can be kept constant even when the output voltage of the linear compensation circuit 21 changes due to adjustment of the compensation amount or the like. , The output of the linear compensation circuit 21 can be adjusted to be constant. Even when the AGC is switched from AGC on to AGC off, the amplifier 1
2 can be suppressed.

In the above-described embodiment, the control circuit 17 adjusts and sets the voltage value of the MGC setting voltage Vm when the AGC is off. However, the voltage value of the MGC setting voltage Vm when the AGC is on is compared. The setting may be made based on the voltage value of the voltage Vc.

In this case, for example, as shown in FIG.
The C circuit 30 has a configuration in which the control circuit 17a takes in the comparison voltage Vc output from the comparator 15. Then, the control circuit 17a takes in the comparison voltage Vc when the AGC is on, and based on the acquired comparison voltage Vc, sets the voltage value of the MGC setting voltage Vm such that the output power does not jump up when the AGC is switched off. Set. Here, the control circuit 1
7a sets the voltage value of the MGC setting voltage Vm to the same value (or substantially the same value) as the acquired voltage value of the comparison voltage Vc.

With this configuration, even when the AGC is switched from AGC on to AGC off, the voltage value of the control signal input to the attenuator 11 is substantially the same. Bounce of output power can be suppressed.

In the above-described embodiment, the AGC circuit 10 for adjusting the amount of attenuation of the attenuator 11 has been described. However, the present invention is applied to an AGC circuit having another configuration such as adjusting the amount of amplification of an amplifier. It goes without saying that you can do it.

Further, in the above-described embodiment, A is applied to a transmission device or a relay device of a television broadcast signal.
Although described as a GC circuit, it is needless to say that the present invention may be applied to other signal transmission devices and relay devices.

[0066]

As described above, according to the present invention, AGC
In the circuit, the control unit includes a detection unit that outputs a detection voltage, a voltage control unit that adjusts a voltage value and outputs an AGC set voltage, and a comparison unit that receives the detected voltage and the AGC set voltage and outputs a comparison voltage. And AGC means for switching between the comparison voltage and the MGC setting voltage and outputting the control signal for controlling the level adjustment means.
The voltage value of the AGC set voltage can be adjusted while the power is off.

When the MGC set voltage is output as the control signal by the switching means (when the AGC is off), the voltage control means is provided when the comparison voltage is selected as the control signal (when the AGC is turned on). If the voltage value of the AGC set voltage is set so that the attenuation of the level adjusting means for inputting the comparison voltage is increased, the output power when the AGC is switched from the AGC off to the AGC on can be reduced. In addition, it is possible to reliably prevent the output power from rising.

The switching timing of the switching means is controlled by the voltage control means, and the voltage control means switches the voltage used as the output control signal of the switching means from the MGC set voltage to the comparison voltage and then to a predetermined value. If the voltage value of the output AGC voltage is gradually changed, the time required to suppress the jump of the output power is adjusted by adjusting the time (or the amount of change in the voltage value) until it reaches a predetermined value. Therefore, appropriate processing can be performed according to the state of the circuit.

A linear compensation circuit for processing an input signal is provided.
When the level adjusting means is configured to adjust the level of the output signal of the linear compensation circuit, the output power is kept constant even when the output voltage of the linear compensation circuit changes due to adjustment of the compensation amount. , The output of the linear compensation circuit can be adjusted to be constant. Also, A
Even when switching from GC-on to AGC-off, it is possible to suppress excessive input to a subsequent circuit or the like.

The voltage control means sets the voltage value of the MGC set voltage, and if the MGC set voltage is also output, the output power when the AGC is off can be made variable.
Further, when the AGC is turned on, the voltage value of the voltage used as the control signal after the AGC is turned off can be adjusted and prepared.

The voltage control means takes in the comparison voltage when the switching voltage is output as the control signal by the switching means, and sets the voltage value of the MGC set voltage based on the voltage value of the comparison voltage. Can set the voltage of the control signal when the AGC is turned off based on the voltage used as the control signal when the AGC is turned on. Therefore, even when the AGC is switched from the AGC on to the AGC off, Bounce of output power can be suppressed.

When the voltage value of the MGC set voltage is set to be substantially the same as the voltage value of the taken-in comparison voltage, the voltage control means may switch the AGC from the AGC on to the AGC off. Since the voltage value of the voltage of the control signal input to the attenuation means before and after the switching is substantially the same, it is possible to suppress the output power from rising.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an example of a configuration of an AGC circuit according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating an example of a configuration of an AGC circuit according to another embodiment of the present invention.

FIG. 3 is a block diagram showing an example of another configuration of the AGC circuit according to another embodiment of the present invention.

FIG. 4 is a block diagram illustrating an example of a configuration of a conventional AGC circuit.

[Explanation of symbols]

 10, 20, 30 AGC circuit 11 Attenuator 12 Amplifier 13 Distributor 14 Detector 15 Comparator 16 Switch 17, 17a Control circuit 21 Linear compensation circuit

Claims (7)

[Claims] A level adjusting means for adjusting a level of an input signal in accordance with a control signal; a distribution means for distributing a part of an output signal; and a level adjusting means for outputting the control signal to the level adjusting means. An AGC circuit including a control means for controlling an adjustment amount of the AGC, wherein the control means outputs a detection voltage of a power corresponding to the power of the signal distributed by the distribution means, Voltage control means for outputting a set voltage;
Comparing means for receiving the detection voltage and the AGC set voltage and outputting a comparison voltage;
A switching means for switching between a GC setting voltage and outputting the control signal as the control signal. 2. The voltage control means according to claim 1, wherein when the switching means outputs the MGC set voltage as a control signal, when a comparison voltage is selected as the control signal, the level control means inputs the comparison voltage. 2. The AGC circuit according to claim 1, wherein the voltage value of the AGC set voltage is set so that the amount increases. 3. The switching timing of the switching means is controlled by a voltage control means, and the voltage control means outputs an output control signal of the switching means to M
3. The AGC circuit according to claim 2, wherein after switching from the GC setting voltage to the comparison voltage, the voltage value of the output AGC voltage is gradually changed until the voltage reaches a predetermined value. 4. The AGC circuit according to claim 1, further comprising a linear compensation circuit for processing the input signal, wherein the level adjusting means adjusts the level of the output signal of the linear compensation circuit. 5. The voltage control means sets a voltage value of an MGC setting voltage and outputs the MGC setting voltage as well.
An AGC circuit according to claim 4. 6. The voltage control means, when the switching means outputs a comparison voltage as a control signal, fetches the comparison voltage and changes the voltage value of the MGC set voltage based on the voltage value of the comparison voltage. The AG according to claim 5, which is set.
C circuit. 7. The AGC circuit according to claim 6, wherein the voltage control means sets the voltage value of the MGC setting voltage to be substantially the same as the voltage value of the taken comparison voltage.