Frequency selection and control

Details Frequency selection and control Frequency selection and control

1974-09-09

1976-06-08

Griffin, Robert L.

Tuners

Tuner unit with electromagnetic operator

Predetermined center frequency selector

325470, 334 11, H04B 132

Patent

active

039626407

ABSTRACT:
An automatic oscillator frequency control is provided for operations such as employed in channel selection in radio and television receiver systems. A code is stored representative of a selected frequency band within which a selected channel is located. The frequency of an oscillator is varied monotonically from a reference frequency at one extremity of a selected frequency range successively to traverse a plurality of such frequency bands. A frequency marker is generated at the margin of each band and the markers are counted. The number of counted markers is compared with the stored code to generate a control state. In response to the control state, a pattern control causes it to dither between limits of the selected band until a signal is encountered at the selected frequency within the selected band. At that point, the oscillator is locked to the frequency of the received signal.
In a preferred embodiment, the frequency markers are generated by use of an interferometer, preferably of the surface wave device type wherein a pair of sensor arrays are spaced to sense acoustic waves at the oscillator frequency and are mixed to produce voltage nulls at the margin of each of a plurality of frequency bands of uniform width. Three control loops are provided, an acquisition loop, a control loop and a tracking loop. The loops are asynchronous and provide for operation without imposition of critical time responses in the manual control thereof.

REFERENCES:
patent: 3496473 (1970-02-01), Seppeler et al.
patent: 3859599 (1975-01-01), Peil
patent: 3864636 (1975-02-01), Fukuda et al.

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