Low-frequency radio navigation system

Details Low-frequency radio navigation system Low-frequency radio navigation system

1981-03-06

1983-08-02

Blum, Theodore M.

Communications: radio wave antennas

Antennas

Balanced doublet - centerfed

364452, G01S 130

Patent

active

043969186

ABSTRACT:
A method of CW navigation is provided using four transmitters (TR1-TR4) operating at sufficiently low frequencies to assure essentially pure groundwave operation. The transmitters are keyed to transmit constant bursts (1/4 sec) in a time-multiplexed pattern with phase modulation of at least one for identification of the transmitters with the ability to identify the absolute phase of the modulated transmitter(s) and the ability to modulate low-rate data for transmission. The transmitters are optimally positioned to provide groundwave coverage over a service region of about 50.times.50 km for the frequencies selected in the range of 200-500 kHz, but their locations are not critical because of the beneficial effect of overdetermination of position of a receiver (R) made possible by the fourth transmitter. Four frequencies are used, at least two of which are selected to provide optimal lane resolution. All transmitters are synchronized to an average phase as received by a monitor receiver (M).

REFERENCES:
patent: 3303501 (1967-02-01), Mahoney
patent: 3974502 (1976-08-01), Phipps
patent: 4028703 (1977-06-01), Honore et al.
patent: 4105262 (1977-03-01), Etcheverry et al.

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