Abstract A timing recovery circuit at a receiver provides fine and coarse phase correction in the receiver''s local oscillator. The coarse correction adds pulses to the local oscillator''s output after it has been divided in frequency whenever the reduced frequency pulses appear outside of a timing window created from a pilot signal sent with the information signal. The fine phase correction adds or deletes pulses in the output of the local oscillator whenever the timing pulses, derived from the output of the coarse phase corrector, do not coincide with data threshold crossings of the information signal. The receiver''s timing pulses train is the reduced frequency pulse train resulting from dividing the frequency output of the course phase corrector. The invention herein described was made in the course of Air Force Contract F30602-67C-0168.
In a receiver, a timing recovery circuit wherein the received signal comprises an information signal and a pilot signal including: oscillator means supplying a high frequency pulse; threshold means determining when the information signal crosses data level thresholds; fine phase correction means connected to said threshold means and to said source of high frequency pulses, inserting and deleting pulses in said stream of high frequency pulses when said threshold means indicate a data level threshold crossing; divider means connected to the output of said fine phase correction means producing output pulses of lower frequency in phase with the output of said fine phase correction means; and coarse phase correction means connected to said divider means inserting or deleting pulses in said train of low frequency pulses when said pulses are sufficiently out of phase with said pilot tone.
Claim 2
Dependent Claim
138 words
In a receiver, a timing recovery circuit wherein the received signal comprises an information signal and a pilot signal including: oscillator means supplying a high frequency pulse; threshold means determining when the information signal crosses data level thresholds; fine phase correction means connected to said threshold means and to said source of high frequency pulses, inserting and deleting pulses in said stream of high frequency pulses when said threshold means indicate a data level threshold crossing; divider means connected to the output of said fine phase correction means producing output pulses of lower frequency in phase with the output of said fine phase correction means; and coarse phase correction means connected to said divider means inserting or deleting pulses in said train of low frequency pulses when said pulses are sufficiently out of phase with said pilot tone.
Claim 3
Dependent Claim
24 words
A device as in claim 1 including: divider means connected to the output of said coarse phase correction means producing a low frequency pulse.
Claim 4
Dependent Claim
48 words
A device as in claim 1, said coarse phase correction means including: means receiving said pilot tone and producing therefrom a pilot window centered about said pilot tone; and said coarse phase correction means adding pulses when said low frequency pulse train occurs outside of said timing window.
Claim 5
Dependent Claim
25 words
A device as in claim 3 wherein: said fine phase correction includes means inserting or deleting pulses only during the occurrence of said timing window.