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Pseudo Noise Automatic Gain Control Circuit

IP.com Disclosure Number: IPCOM000093485D
Original Publication Date: 1967-Oct-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 57K

Publishing Venue

IBM

Related People

Sampson, CE: AUTHOR

Abstract

The AGC circuit, useful in a pseudo-noise PS receiver, utilizes a narrow banding technique to capture signal power even in the presence of much larger interfering signals. The receiver AGC voltage is then derived from the narrow banded signal.

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Pseudo Noise Automatic Gain Control Circuit

The AGC circuit, useful in a pseudo-noise PS receiver, utilizes a narrow banding technique to capture signal power even in the presence of much larger interfering signals. The receiver AGC voltage is then derived from the narrow banded signal.

Drawing A shows the PS-AGC circuit for a bi-phase modulated system. Drawings B...D show the signal and noise spectral densities and the bandwidths at critical points in the circuit.

In drawing A, a PS + 2f(s) signal is derived from the local PS generator and mixed with the signal output of the IF amplifier chain. In the mixing operation, the PS is stripped from the incoming signal and the signal is then fed into the squaring device at 2. At this point, the signal has a 180 degrees phase ambiguity and the simplified spectrum is shown in drawing 13. The signal is then squared. The spectrum at 3 after the squaring operation of drawing A is shown in drawing
C. The signal is then fed through a narrow-band filter which selects the second harmonic consisting of a single carrier component. The bandwidth of this filter is compatible with the rise and fall time of the desired AGC characteristic. Drawing D shows the spectral components and AGC bandwidth at the output of the narrow-band filter. The signal from the narrow-band filter is then fed to the rectifier and AGC voltage generator where the AGC voltage is derived and sent to each amplifier stage in the IF chain and to the RF section.

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