Automatic frequency control device for tuning an intermediate fr

Details Automatic frequency control device for tuning an intermediate fr Automatic frequency control device for tuning an intermediate fr

1995-07-24

1998-01-06

Chin, Stephen

Pulse or digital communications

Receivers

Automatic frequency control

4551822, 4551922, 4551961, H04L 2706

Patent

active

057063150

ABSTRACT:
In an automatic frequency control device for tuning the frequency of an intermediate frequency (IF) signal to a desired or target frequency, a frequency mixer subtracts the frequency of a received signal coming in through an antenna from the frequency of a local oscillation signal output from a voltage controlled oscillator. A reference oscillator outputs a reference oscillation signal on the basis of a control voltage from a digital/analog converter. The local oscillation signal from the voltage controlled oscillator is synchronous in phase to the reference oscillation signal. A frequency measurement circuit measures the frequency of the IF signal. A subtracter subtracts the frequency of the IF signal from the target frequency and thereby produces a frequency error. A multiplier multiplies the frequency error by, in a proportional relation between the frequency of the IF signal and a voltage represented by a control voltage signal, the reciprocal of a gradient of the voltage of the control voltage signal to the frequency of the IF signal. An adder adds the control voltage signal to the output of the multiplier, thereby correcting the control voltage signal. The digital/analog converter converts the control voltage signal to an analog signal and thereby outputs the control voltage.

REFERENCES:
patent: 3085210 (1963-04-01), Etal
patent: 3626301 (1971-12-01), Develet
patent: 4556988 (1985-12-01), Yoshisato
patent: 5457716 (1995-10-01), Ang et al.
patent: 5461645 (1995-10-01), Ishii
British Search Report.

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