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Digitally Controlled Automatic Gain Control Circuit

IP.com Disclosure Number: IPCOM000084488D
Original Publication Date: 1975-Nov-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Braquet, H: AUTHOR [+2]

Abstract

Shown on the drawing is an automatic gain control circuit, wherein the input signal power is measured at the input side of the circuit and converted to provide the gain control signal.

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Digitally Controlled Automatic Gain Control Circuit

Shown on the drawing is an automatic gain control circuit, wherein the input signal power is measured at the input side of the circuit and converted to provide the gain control signal.

The input signal received on input terminal 1 is applied to variable-gain amplifier 2 through branch 1a and to a measuring circuit through branch 1b. The measuring circuit comprises a full-wave rectifier 3, a low-pass filter 4, a linear-to- logarithm converter 5, and an analog-to-digital converter 6 having n outputs 6-1 to 6-n connected to amplifier 2.

Rectifier 3 and filter 4 give an indication of the input signal power which is converted into an analog decibel value in converter 5.

This analog value is converted into a n-bit digital value in converter 6, which is used for adjusting the gain of amplifier 2 to a given value depending upon the signal power. Gain of amplifier 2 can be set in 2/n/ steps which are N/2/n/ decibel apart, N being the dynamic range of input signal expressed in decibel.

Amplifier 2 provides a signal on its output 7, a signal, the level of which is maintained constant in the N decibel signal range.

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