Horology: time measuring systems or devices – Time interval – Electrical or electromechanical
Patent
1989-04-11
1990-08-07
Miska, Vit W.
Horology: time measuring systems or devices
Time interval
Electrical or electromechanical
368156, 331 1A, 331 25, G04F 800, H03L 700
Patent
active
049473824
ABSTRACT:
A digital locked loop which can act as a slave clock. The digital loop is able to monitor a master clock signal and adjust its own output to accurately track the frequency of the master clock signal. In addition, the digital loop can generate a highly accurate timing signal in the absence of the master clock. An oscillator supplies a signal having a fixed frequency to a digital synthesizer. The synthesizer treats the oscillator frequency as a known standard. The synthesizer uses that standard to generate an output signal with a different frequency. The frequency of the output signal is chosen so that it is equal to a frequency supplied by an external master clock. The present invention utilizes a digital feedback loop to detect any phase shift between the output signal and the master clock signal. The presence of any phase shift indicates that the frequency of the master clock signal has changed. A microprocessor measures the amount of this phase shift and adjusts the output of the digital synthesizer to equal the new frequency of the master clock signal.
REFERENCES:
patent: 3675146 (1972-07-01), Langham
patent: 4305045 (1981-12-01), Metz et al.
patent: 4354164 (1982-10-01), Gupta
patent: 4521744 (1985-06-01), Yamada et al.
patent: 4538119 (1985-08-01), Ashida
patent: 4563657 (1986-07-01), Qureshi et al.
patent: 4598257 (1986-07-01), Southard
patent: 4743857 (1988-05-01), Childers
Miska Vit W.
Vista Labs, Inc.
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