Oscillators – Automatic frequency stabilization using a phase or frequency... – Afc with logic elements
Patent
1978-03-15
1979-08-07
Grimm, Siegfried H.
Oscillators
Automatic frequency stabilization using a phase or frequency...
Afc with logic elements
307232, 307233R, 328134, 328155, 331 17, 331 27, H03B 304, H03K 520
Patent
active
041639510
ABSTRACT:
In a frequency discriminator for a first and a second input signal of a first and a second frequency, a phase detector produces first and second rectangular pulse sequences. When the first input signal leads the second by 0.degree. through 180.degree., the first pulse sequence takes a predetermined peak value with an instantaneous frequency corresponding to the phase difference while the second one continuously has the peak value. When the first input signal lags behind the second by 0.degree. through 180.degree., the second pulse sequence takes the peak value with the instantaneous frequency while the first one continuously has the peak value. A low-pass filter rejects components of the first pulse sequence which are higher than the first and second frequencies. A high-pass filter has a prescribed cutoff frequency for rejecting lower-frequency components of the low-pass output to produce an output pulse sequence representing in average the difference between the first and second frequencies when the first frequency is higher than the second. Alternatively or additionally, a similar set of a low-pass and a high-pass filter produces a like output pulse sequence when the first frequency is lower than the second. At least one of the output pulse sequences is used as a discriminator output signal either per se or after conversion to a substantially d.c. signal. The frequency discrimination characteristics depend on the prescribed cutoff frequency. In an automatic frequency control (AFC) loop, both d.c. signals may be supplied to a voltage controlled oscillator through a differential circuit.
REFERENCES:
patent: 3514719 (1970-05-01), Rhodes
patent: 3610954 (1971-10-01), Treadway
patent: 3748589 (1973-07-01), Miller
Aihara Shigenobu
Haga Isao
Mizumura Motoo
Grimm Siegfried H.
Nippon Electric Co. Ltd.
Westin Edward P.
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