JP2000165166A - Automatic signal level controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an automatic signal level controller by which a stable output can be obtained even when a level of an input signal is largely fluctuated. SOLUTION: An adder circuit 5 sums an input signal and an adjustment signal with a constant level having a frequency higher or lower than a frequency in a frequency region of the input signal that is outputted from a gain adjustment signal output section 3, an ALC circuit 7 controls a resulting summing signal so as to have a constant level, and then the resulting summing signal whose level is made constant by the circuit 7 is given to a filter 9, from which a signal with frequencies within the frequency range of the input signal is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic signal level control device for automatically controlling the level of an input signal to a constant level.

[0002]

2. Description of the Related Art Conventionally, an automatic signal level control device 101 shown in FIG. 3 is known as an automatic signal level control device.

The automatic signal level control device 101 includes a variable gain amplifier 103 that amplifies an input signal with a variable gain and outputs the amplified signal, and a signal level detection unit 105 that detects the level of the input signal. When a signal is input to the automatic signal level controller 101, the signal level detector 105 detects the signal level and outputs a gain control signal corresponding to the signal level. The variable gain amplifier 103 changes the gain according to the gain control signal so as to decrease the gain when the signal level is high, and increase the gain when the signal level is low, and amplify the input signal so that the output signal level becomes constant. And output.

When there is no input signal, the gain of the variable gain amplifier 103 is maximum, and when the amplitude of the input signal is maximum, the gain of the variable gain amplifier 103 is minimum.

[0005]

However, in the conventional automatic signal level control device 101, for example, from the absence of an input signal to the maximum amplitude level until the gain of the variable gain amplifier 103 is adjusted. Immediately after, the level of the output signal from the variable gain amplifier 103 becomes excessive, and as a result, there is a problem that a stable output cannot be obtained.

[0006] The present invention has been made in view of the above,
It is an object of the present invention to provide an automatic signal level control device capable of obtaining a stable output even when the amplitude level of an input signal fluctuates greatly.

[0007]

According to the first aspect of the present invention,
In order to solve the above problem, an automatic signal level control device that controls a signal level of an input signal to be a constant level generates an adjustment signal having a constant amplitude level having a frequency higher or lower than a frequency range of the input signal. Adjusting signal generating means, an adding means for adding the input signal and the adjusting signal, a level controlling means for controlling the addition result signal to have a constant level, and a frequency of the input signal among the constant level addition result signals. And a signal passing means for passing a signal in the area.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a configuration of an automatic signal level control device 1 according to an embodiment of the present invention.

As shown in FIG. 1, the automatic signal level control device 1 includes a gain adjustment signal output section 3 for outputting a gain adjustment signal, an addition circuit 5 for adding an audio signal and a gain adjustment signal, and a description will be given later. ALC (Automatic L
(Evel Control) circuit 7 and a filter 9 for blocking the passage of the gain adjustment signal.

The gain adjustment signal has a constant frequency that is at least several times or less than the frequency band of the audio signal. The reason for this is to make it easier to cut the gain adjustment signal later with a filter.

The ALC circuit 7 automatically controls the input signal to have a constant level. As shown in FIG. 1, the ALC circuit 7 includes a variable gain amplifier 11 for amplifying the input signal with a gain corresponding to the level of the input signal. , A signal level detector 13 for detecting the level of the input signal.

Next, the operation of the automatic signal level control device 1 will be described with reference to FIG.

The audio signal converted into an electric signal is input to one end of the adding circuit 5. The audio signal is shown in FIG.
The waveform is as shown in FIG. On the other hand, the gain adjustment signal output from the gain adjustment signal output unit 3 is input to the other end of the addition circuit 5. The gain adjustment signal is always output even when no audio signal is output, and when there is no audio signal, the gain adjustment signal is ALC
Input to the circuit 7. The waveform of the gain adjustment signal is shown in FIG.

Next, the addition circuit 5 adds the audio signal and the gain adjustment signal, and outputs the result to the ALC circuit 7. When a signal is input to the ALC circuit 7, the signal level detector 13 detects a change in the signal level and outputs a gain control signal corresponding to the change in the signal level. Then, the variable gain amplifier 11 changes the gain according to the gain control signal, amplifies the input signal level, and outputs the amplified signal.

Here, an operation when an audio signal of a predetermined level or higher is output from a state where there is no audio signal will be described.

When there is no audio signal, the gain adjustment signal is input to the variable gain amplifier 11 of the ALC circuit 7 via the addition circuit 5. On the other hand, the signal level detecting section 13 detects the level of the gain adjustment signal and outputs a gain control signal corresponding to the level of the gain adjustment signal. The gain of the variable gain amplifier 11 is adjusted so that the amplitude level of the gain adjustment signal is constant.
1 amplifies an input signal and outputs a signal of a certain level. Even when there is no audio signal, since the gain adjustment signal is input to the ALC circuit 7, the variable gain amplifier 1
The gain of 1 indicates a constant value lower than the maximum value, and it is possible to prevent the gain from being significantly increased.

When an audio signal of a predetermined level or more is input, the adding circuit 5 adds the audio signal and the gain adjustment signal, and outputs the result to the ALC circuit 7. ALC
When a signal is input to the circuit 7, the signal level detector 13
Detects a change in the signal level and outputs a gain control signal corresponding to the signal level. Then, the variable gain amplifier 11 changes the gain according to the gain control signal.
The gain of the variable gain amplifier 11 decreases as the level of the audio signal increases.

Next, a description will be given of an operation in the case where the audio signal disappears from the state where the audio signal of a predetermined level or more is input.

In the state where the audio signal is being input, the audio signal is input to one end of the addition circuit 5, while the gain adjustment signal is input to the other end of the addition circuit 5. The addition circuit 5
Add the audio signal and gain adjustment signal, and add the result to AL
Output to the variable gain amplifier 11 of the C circuit 7. On the other hand, the signal level detector 13 detects a change in the level of the input signal to the ALC circuit 7 and outputs a gain control signal corresponding to the level of the input signal. And the variable gain amplifier 11
The gain of is adjusted according to the amplitude level of the input signal,
The variable gain amplifier 11 amplifies an input signal and outputs a signal of a certain level. The higher the level of the audio signal,
The gain of the variable gain amplifier 11 decreases.

When there is no audio signal, the gain adjustment signal is input to the variable gain amplifier 11 of the ALC circuit 7 via the addition circuit 5. On the other hand, the signal level detecting section 13 detects the level of the gain adjustment signal and outputs a gain control signal corresponding to the level of the gain adjustment signal. Then, the gain of the variable gain amplifier 11 is adjusted so that the amplitude level of the gain adjustment signal is constant.
1 amplifies an input signal and outputs a signal of a certain level. Even when there is no audio signal, since the gain adjustment signal is input to the ALC circuit 7, the variable gain amplifier 1
The gain of 1 indicates a constant value lower than the maximum value, and it is possible to prevent the gain from being significantly increased.

As a result, even when the audio signal fluctuates remarkably, it is possible to make adjustment without a large gain fluctuation, and it is possible to output a signal that is smooth and comfortable.

The output signal from the variable gain amplifier 11 is input to the filter 9. From filter 9,
The passage of the gain adjustment signal is blocked, and a fixed level audio signal is output.

In this embodiment, the case where the audio signal is controlled so as to have a constant level has been described.
The present invention is not limited to this. Even when the present invention is applied to data communication or the like, the gain adjustment signal is a kind of AGC (Auto
It plays the role of a pilot signal in Omatic Gain Control, and can maintain a constant level through various lossy lines.

[0025]

According to the first aspect of the present invention, the input signal and the adjustment signal having a constant amplitude level having a frequency higher or lower than the frequency domain of the input signal are added, and the addition result signal is set to a predetermined level. By passing the signal in the frequency domain of the input signal among the addition result signals of a certain level, even if a high-level signal is input, a stable output is obtained without large gain fluctuation. Can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an automatic signal level control device 1 according to an embodiment of the present invention.

2 shows a waveform (a) of an audio signal input to an automatic signal level control device 1 and a waveform (b) of a gain adjustment signal output from a gain adjustment signal output unit 3. FIG.

FIG. 3 is a configuration diagram of a conventional automatic signal level control device 101.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Automatic signal level control device 3 Gain adjustment signal output part 5 Addition circuit 7 ALC circuit 9 Filter

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5J092 AA02 CA11 FA02 KA00 KA26 KA41 SA13 TA01 TA06 VL03 5J100 JA01 KA05 LA00 LA01 LA08 QA01

Claims (1)

[Claims] 1. An automatic signal level control device for controlling a signal level of an input signal to be a constant level, wherein the adjustment for generating an adjustment signal having a constant amplitude level having a frequency higher or lower than a frequency range of the input signal. Signal generation means; addition means for adding the input signal and the adjustment signal; level control means for controlling the addition result signal to be a constant level; An automatic signal level control device comprising: signal passing means for passing a signal.