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# Variable Frequency Control Circuit

IP.com Disclosure Number: IPCOM000096169D
Original Publication Date: 1963-Jan-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 25K

IBM

## Related People

Braun, RE: AUTHOR [+2]

## Abstract

The output pulses of this circuit vary in frequency in response to the variation of frequency of an input signal. Ordinary variable frequency circuits respond only to a limited range of frequencies. This circuit tracks wide frequency variations.

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Variable Frequency Control Circuit

The output pulses of this circuit vary in frequency in response to the variation of frequency of an input signal. Ordinary variable frequency circuits respond only to a limited range of frequencies. This circuit tracks wide frequency variations.

The input signal has a dual frequency characteristic. That is, if the signal is to contain information, a binary 0 is contained in a unit frequency and a binary 1 is contained in twice the unit frequency. Thus, to detect any frequency variation, the input signal is first divided by two and applied to an FM demodulator. A waveform having an amplitude proportional to the variation of the frequency from the nominal frequency is provided by the demodulator. This is applied as a control voltage to a voltage controlled oscillator. The oscillator has a nominal frequency which is much greater than the nominal frequency of the input waveform in order that a total change in frequency of the input waveform requires only a small percentage change in the voltage controlled oscillator.

As an example, if the input waveform is normally 3 mc, the voltage controlled oscillator may operate at 30 mc. When a 100% change occurs in the input frequency, i. e., 3 mc, only a ten per cent change occurs in the voltage controlled oscillator. The range of frequency response of the voltage controlled oscillator is, therefore, substantially reduced as compared with the ordinary circuit.

The output waveform of the volta...