Pulse or digital communications – Spread spectrum – Direct sequence
Patent
1991-01-14
1992-07-07
Chin, Stephen
Pulse or digital communications
Spread spectrum
Direct sequence
370 48, 455 511, H04L 700
Patent
active
051289717
ABSTRACT:
An improved method and apparatus for synchronizing a receiver oscillator with a transmitter oscillator is provided. The receiver is arranged with a counter driven by the receiver oscillator; and the transmitter is arranged with a counter driven by the transmitter oscillator. The transmitter sends a start signal to the receiver and simultaneously records the current reading of its counter. Later, the transmitter sends a stop signal to the receiver and simultaneously records the current reading of its counter. The transmitter then computes the elapsed count, and sends this value to the receiver as the "transmitter reading". Upon receipt of the start signal, the receiver records the current reading of its counter. Later, upon receipt of the stop signal, the receiver records the current reading of its counter, and then computes the elapsed count. Upon receipt of the "transmitter reading", the receiver is then able to determine the error of its own oscillator relative to that of the transmitter site oscillator as: ##EQU1## where A and B are predetermined constants which may be used to normalize the receiver and transmitter counter speeds to each other or to a third set of units. The transmitter then warps its own oscillator based on the calculated error. In an alternate embodiment, the transmitter resets its counter to zero upon sending the first start signal; and the receiver resets its counter to zero upon receipt of this signal.
REFERENCES:
patent: 3388216 (1968-06-01), Brooke et al.
patent: 3430204 (1969-02-01), Milford
patent: 4792966 (1988-12-01), Ballweg
patent: 4852128 (1989-07-01), Lill
Chin Stephen
Egan Wayne J.
Motorola Inc.
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