Reliable cycle selection in LORAN-C system

Details Reliable cycle selection in LORAN-C system Reliable cycle selection in LORAN-C system

1974-09-03

1976-01-20

Wilbur, Maynard R.

Communications: radio wave antennas

Antennas

Balanced doublet - centerfed

G01S 124

Patent

active

039342549

ABSTRACT:
Reliable cycle selection is achieved with LORAN-C pulses received under low signal-to-noise conditions. A tracking pulse is generated at the LORAN-C pulse repetition rate and is intended to be time-coincident with the end of the third 100 KHz carrier cycle in each received pulse. Sampling pulses are generated one-quarter and three quarters of a cycle before and after the tracking pulse and are used to sample a hard-limited, envelope-derived version of the received signal in which a phase reversal occurs at the start of the fourth carrier cycle. If the tracking pulse is coincident with the end of the third carrier cycle, a unique pattern of binary levels is sampled by the four sampling pulses. If the tracking pulse is too early or too late, corresponding early (left) and later (right) sampled level patterns result. Left and right occurrences of the tracking pulse are individually counted for a predetermined number of received LORAN-C pulses after which the difference between left and right counts is examined. If this difference is less than a pre-established number, the tracking pulse is properly positioned; if the difference exceeds the pre-established number, the track pulse is shifted in time accordingly.

REFERENCES:
patent: 2811718 (1957-10-01), Frank
patent: 2873445 (1959-02-01), Palmer
patent: 3044064 (1962-07-01), Durbin
patent: 3325810 (1967-06-01), Frank et al.

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