Patent
1975-01-27
1976-01-20
Britton, Howard W.
325420, 325423, H04B 116
Patent
active
039342050
ABSTRACT:
This invention relates to a gated frequency difference detector for use in a frequency lock loop. The gated frequency difference detector consists of a dual output hybrid quadrature mixer, two parallel video signal processing channels, a digital phase/frequency detector, a digital scaler and a digital-to-analog converter. The difference in frequency between the RF input and the output of a local oscillator is measured. Two orthogonal frequency difference outputs are first generated, one of which either leads or lags the other depending on the sense of the difference. Signals are then bandwidth limited and amplified in two video channels and converted to logic levels. The phase and frequency are finally digitally detected and processed to generate a bipolar voltage proportional to the magnitude and sense of the frequency difference.
The digital detection and processing apparatus includes in each channel a positive, zero, and negative threshold detector, the outputs of which are converted to a four-bit binary code.
REFERENCES:
patent: 3403355 (1968-09-01), Takada
patent: 3646446 (1972-02-01), Rittenbach
patent: 3667050 (1972-05-01), Gibson
patent: 3673321 (1972-06-01), Janssen
patent: 3701948 (1972-10-01), McAuliffe
patent: 3863156 (1975-01-01), Bogert
Britton Howard W.
Ingrassia Vincent
International Telephone and Telegraph Corporation
Lombardi, Jr. Menotti J.
Ng Jin F.
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