Pulse or digital communications – Spread spectrum – Direct sequence
Patent
1988-01-21
1989-08-29
Griffin, Robert L.
Pulse or digital communications
Spread spectrum
Direct sequence
329122, 375 96, H04L 702
Patent
active
048624845
ABSTRACT:
A clock recovery circuit for producing a clock signal from a baseband information signal that has a data rate R. The information signal is frequency converted to a predetermined intermediate frequency by mixing the information signal with a tunable local oscillator signal having a frequency f. The resulting converted signal is bandpass filtered to extract the clock spectral line at f+R/2. The resulting signal is then frequency doubled, producing a signal of 2f+R. After passing through another narrowband filter (in one embodiment a phase-locked loop) the doubled signal is reconverted to produce the spectral line at R (the recovered clock), filtered to remove the unwanted products produced in the reconversion process, and passed through a comparator to sharpen the signal edges. Using this technique, the clock signal can be recovered from information signals of different data rates without having to switch from one bandpass filter to another when the frequency of the information signal changes.
REFERENCES:
patent: 4072905 (1978-02-01), Keelty
patent: 4455665 (1984-06-01), Kromer, III
patent: 4575860 (1986-03-01), Scordo
patent: 4606053 (1986-08-01), Schroder
patent: 4653074 (1987-03-01), Griffin
patent: 4675881 (1987-06-01), Chung
DeAngelis, Jr. John L.
Griffin Robert L.
Harris Corporation
Huseman Marianne
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