JPH04156708A - Automatic gain control amplifier - Google Patents

Abstract

PURPOSE:To keep a fixed output level without compressing the output level of each carrier signal in the case that a multi-carrier signal is inputted and amplified by controlling the gain of an amplifier by making the difference of detected voltage a control signal. CONSTITUTION:The multi-carrier signal inputted from an input terminal 11 is amplified by a variable gain type amplifier 3, and is outputted from an output terminal 12, and an input level is level-detected by a detector 1, and the output level is detected by the detector 4, and respective outputs are inputted to a differential amplifier 2. The amplifier 2 outputs the level difference of this input level and this output level to a gain control part 5, and the gain control part 5 controls the amplifier 3 so that this level difference of the input/output levels becomes constant. Accordingly, even if the number of the carriers of an input signal is increased, this increase is detected by the detector 1 of the input, and the amplifier 3 is controlled by the difference from the output level to be increased similarly. Thus, the output level per one carrier can be kept constant.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an automatic gain control amplifier, and more particularly to an automatic gain control amplifier used in a transmitter to amplify a multicarrier signal.

[Conventional technology]

Conventionally, this type of automatic gain control amplifier has, as shown in FIG. 2, 11 an input terminal, 2 an output terminal, 3 a variable gain amplifier, 4 a detector, and 5 a gain control section. Next, the operation of the conventional example will be explained. A multicarrier signal inputted through the input terminal 11 is amplified by the variable gain amplifier 3 and outputted to the output terminal 12. The output level is detected by a detector 4, and the gain control section 5 controls the gain of the variable gain amplifier 3 so that the output level is constant. Here, the output level of each multicarrier signal at the output terminal 12 was kept constant.

[Problem to be solved by the invention]

In the conventional automatic gain control amplifier described above, since the Kugata signal is a multicarrier signal, the power phase of all carrier signals obtained by adding each carrier signal is detected, and the detection level corresponding to that power phase becomes a constant level. The gain is controlled as follows. Therefore, there is a drawback that the level per carrier signal becomes 1/the number of multicarriers.

An object of the present invention is to provide an automatic gain control amplifier that can maintain a constant output level without compressing the output level of each carrier signal when a multicarrier signal is input and amplified.

[Means to solve the problem]

The automatic gain control amplifier of the present invention includes an amplifier whose gain is varied by a control signal applied to a variable gain control terminal, a first detector that detects a multicarrier signal level input to the amplifier, and an output of the amplifier. It has a second detector that detects the level, and a differential amplifier that outputs the difference between the detected voltages of the first and second detectors, and uses the difference between the detected voltages as a control signal to control the gain of the amplifier. It's in control.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention. In FIG. 1, 11 is an input terminal, 12 is an output terminal, 3 is a variable gain amplifier, 1 and 4 are detectors, 2 is a differential amplifier, and 5 is a gain control section.

Next, the operation of this embodiment will be explained. A multicarrier signal input from the input terminal 11 is amplified by the variable gain amplifier 3 and output from the output terminal 12. The input level is detected by a wave detector 5, the output level is detected by a wave detector 4, and the respective outputs are input to the differential amplifier 2. The differential amplifier 2 outputs the level difference between the input level and the output level to the gain control section 5. The gain control section 5 controls the variable gain amplifier 3 so that this input/output level difference is constant. Therefore, even if the number of carriers in the input signal increases, it is controlled by the difference between the amount of increase and the output level detected by the input detector 1, which is also increasing.
The output level per wave can be held constant.

〔Effect of the invention〕

As explained above, the present invention includes a detector for detecting an input level and a differential amplifier that amplifies the difference between the input level and the output level. Gain is controlled. Therefore, there is an effect that the output level per wave of the multicarrier signal can be made constant.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional automatic gain control amplifier. 1.4... Detector, 2... Differential amplifier, 3... Variable gain amplifier, 5... Gain control section, 11... Input terminal, 12... Output terminal.

Claims (1)

[Claims] an amplifier whose gain is varied by a control signal applied to a variable gain control terminal; a first detector that detects a multicarrier signal level input to the amplifier; and a second detector that detects an output level of the amplifier. and a differential amplifier that outputs the difference between detected voltages of the first and second detectors, and controls the gain of the amplifier using the difference between the detected voltages as a control signal. Gain control amplifier.