JPH02285803A - Automatic level control circuit - Google Patents

Abstract

PURPOSE:To improve the response speed against a change in the frequency or temperature by preparing the frequency characteristic or temperature characteristic of an amplifier in advance as a correction table, applying coarse gain correction through the use of the table and using minute adjustment of gain by a feedback loop in common. CONSTITUTION:Frequency correction and temperature correction tables 7, 9 are tables for gain correction based on the frequency characteristic and the temperature characteristic of an amplifier measured in advance and generate gain correction quantities VF, VT. The correction quantities VF, VT are added by an adder 10 to control a variable attenuator 1. Through the operation above, coarse output level control correcting the frequency characteristic and temperature characteristic of the amplifier 2 at a high speed is applied. Then the level is compared with a reference level VR from a reference voltage generator 6 at a level comparator 6 to obtain a gain correction VE correcting the residual error. The correction VE is added to the coarse correction quantities VF, VT at the adder 10 to apply accurate level control.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an automatic level control circuit that controls the output level of an amplifier to be constant.

[Conventional technology]

FIG. 3 is a system diagram showing an example of a conventional automatic level control circuit. In the diagram, (1) is a variable attenuator that controls the amplifier input level, (2) is the amplifier, and (3) is the amplifier output level. A coupler to take out a part, (4) is a level detector, (
5) is a level comparator that compares the level detector output with a reference voltage, and (6) is a reference voltage generator.

Next, the operation will be explained. The input signal is passed through a variable attenuator (1
) is input to the amplifier (2). Generally, the gain of an amplifier has frequency characteristics and temperature characteristics, and if left as is, the output level will fluctuate in response to changes in frequency and temperature. Therefore, in order to control the output level to be constant, a part of the output is taken out by a coupler (3) and detected by a level detector (4) to obtain information on the output level. On the other hand, the reference voltage generator (6) generates a reference voltage 5 corresponding to the required amplifier output, and the level detector output and this reference voltage are compared in the level comparator (5) and an error voltage is generated. vE, and by configuring one or more feedback loops that control the variable attenuator (1), it is possible to control the output level to be constant despite changes in frequency and temperature.

[Problem that the invention seeks to solve]

The conventional automatic level 1blN31 circuit is configured as described above, so in order to increase the response speed so that it can cope with large and sudden changes in frequency and temperature, it is necessary to
There was a problem that the gain had to be large, the system was likely to become unstable, and as a result, the response speed could not be increased very much.

The automatic level control circuit according to the present invention solves the above-mentioned problems.
A correction table is prepared in the ad 0nly Memory), etc., and coarse gain correction is performed using this table based on the frequency information and temperature information at that time, and fine adjustment of the gain using a conventional feedback loop is also used. It is something.

[Effect]

The automatic level control circuit according to the present invention performs high-speed level control over a wide range by rough gain correction using the above-mentioned frequency or temperature correction table, and also performs high-speed level control over a wide range by using a feedback loop similar to the conventional one to deal with residual errors in this rough adjustment. By finely adjusting the gain, high-speed and highly accurate level control is achieved.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, (1) is a variable attenuator that controls the amplifier input level, (2) is an amplifier, (3) is a coupler that takes out a part of the amplifier output, and (4) is a level detector that detects the output level of the amplifier. , (5) is a level comparator that compares the level detector output and the reference voltage vlI, (6) is a reference voltage generator, (7) is a frequency correction table for the amplifier, and (8) is the amplifier or its vicinity. (9) is a temperature correction table, and OI is an adder.

Next, the operation of this embodiment will be explained. The frequency correction table (7) is a table of gain correction amounts prepared based on the frequency characteristics of the amplifier that have been measured in advance.According to the frequency information F manually input from the outside, the frequency correction table (7) calculates the gain correction amount V at the frequency.

occurs. The temperature correction table (9) is a table of gain correction amounts prepared based on the temperature characteristics of the amplifier measured in advance, and the gain correction amount v7 at the temperature is determined according to the temperature information T from the temperature sensor (8). occurs. These corrections NV and v7 are added in an adder OI, controlled by a variable attenuator (11), and controlled by a level detector (4).
), and is further compared with the reference level (1) from the reference voltage generator (6) in the level comparator (5) to correct residual errors. A gain correction amount V is obtained. This correction amount v2 is converted into the above-mentioned coarse correction amount V,
, V, for precise level control.

Note that in this embodiment, the variable attenuator (1) is replaced by the amplifier (2).
Although it is placed before the amplifier (2) and the coupler (3), the same effect can be achieved even if it is placed between the amplifier (2) and the coupler (3). Furthermore, it goes without saying that for application examples where there is no frequency change or application examples where temperature change is small, the same effect can be obtained even if the temperature correction table and the frequency correction table are omitted, respectively.

Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a system diagram of this embodiment, and each component and its operation are the same as those of the first embodiment shown in FIG.
The characteristic point of this embodiment is that the correction IV which is each output of the frequency correction table (7) and the temperature correction table (9)
After adding F and V in adder 01, amplifier (2)
The gain of the amplifier (2) is directly controlled by inputting it to the bias controller 0υ that controls the bias voltage of the amplifier (2). Precise correction of the gain is achieved by detecting the amplifier output level and adjusting the error from the reference level using the variable attenuator (1), as in the first embodiment.
Correct with.

Note that three corrections WVr, r, Vt (
In this case, the gain control by the variable attenuator (11 or the bias controller aυ) may be performed by either the variable attenuator (11) or the bias controller aυ. It is.

〔Effect of the invention〕

As described above, according to the present invention, in addition to level control using a conventional feedback loop, level correction is performed using a frequency correction table or a temperature correction table. This has the effect of providing a level control circuit.

This is a schematic diagram.

In these figures, il+ is a variable attenuator, [21 is an amplifier, (3) is a coupler, (4) is a level detector, and (5)
is a level comparator, (6) is a reference voltage generator, (7) is a frequency correction table, (8) is a temperature sensor, (9) is a temperature correction table, aI is an adder, and aυ is a bias controller.

In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Figure 1

Claims (2)

[Claims] (1) a level detector that detects the output level of the amplifier; a level comparator that outputs a gain correction amount for the amplifier based on the difference between the output of the level detector and a reference level; and a frequency of the input signal of the amplifier. a correction table having at least one of a frequency correction table that outputs a correction amount for the frequency characteristics of the amplifier based on a measured value or a temperature correction table that outputs a correction amount for the temperature characteristics of the amplifier based on a temperature measurement value of the amplifier; and a variable attenuator that attenuates the input or output of the amplifier according to the correction amount of the correction table and the gain correction amount of the level comparator. (2) a level detector that detects the output level of the amplifier; a level comparator that outputs a gain correction amount for the amplifier based on the difference between the output of the level detector and a reference level; and a frequency of the input signal of the amplifier. a correction table having at least one of a frequency correction table that outputs a correction amount for the frequency characteristics of the amplifier based on a measured value or a temperature correction table that outputs a correction amount for the temperature characteristics of the amplifier based on a temperature measurement value of the amplifier; and a bias controller that controls the amplification factor by controlling the bias voltage of the amplifier according to the correction amount of the correction table and the gain correction amount of the level comparator. .