The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 07, 1990
Filed:
Apr. 11, 1989
Austin H Lesea, San Jose, CA (US);
Vista Labs, Inc., San Jose, CA (US);
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.