Counting circuit for determining the incoming frequency or recei

Details Counting circuit for determining the incoming frequency or recei Counting circuit for determining the incoming frequency or recei

1977-12-07

1980-03-18

Griffin, Robert L.

Telecommunications

Receiver or analog modulated signal frequency converter

Signal selection based on frequency

H04B 106

Patent

active

041936868

ABSTRACT:
The counting circuit is particularly useful in a high-frequency superhet receiver including IF filters, such as ceramic filters, available as completed units having definite, pre-aligned IF values, and is of the type in which the oscillations of an AM or FM local oscillator, the frequency of which differs from that of the received signal by the frequency of the IF stage of the receiver, are counted periodically by an electronic counter with each such count taking place within a predetermined gate time. In such a counting circuit, during the counting operation, a number of oscillations correspondng to a predetermined fixed number of oscillations occurring at the IF of the receiver is either subtracted from or added to the oscillations of the AM or FM oscillator so that the count of the counter indicates the incoming frequency or received channel. The gate time is determined by the pulse duration of periodically generated pulses and, in accordance with the invention, deviations of the actual IF of the IF stage relative to the predetermined fixed value of the IF taken into account during the counting operation, are compensated by shifting the leading edge, determining the beginning of the gate time, to vary the duration of the periodically generated pulses. Such shifting of the leading edge can be effected in an RC circuit including either a potentiometer, fixed value voltage dividers, or a plurality of potentiometers selected by selector switches.

REFERENCES:
patent: 3949307 (1976-04-01), Klank
patent: 3991382 (1976-11-01), Iida et al.
patent: 4077009 (1978-02-01), Klank

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