Automatic direction finding system

Details Automatic direction finding system Automatic direction finding system

1976-04-26

1977-08-09

Wilbur, Maynard R.

Communications: radio wave antennas

Antennas

Balanced doublet - centerfed

343100SA, G01S 502

Patent

active

040414965

ABSTRACT:
An automatic direction finding system utilizing the doppler principle for indicating the bearing of a radio transmission. The system includes an antenna array of three or more antenna elements equally spaced around a circular path. The antenna elements are connected to the input of a receiver through electronically controlled, variable attenuators which are individually adjusted at the same frequency but differing phases so that the array effectively simulates a single antenna element physically moving along a circular path at a fixed modulation frequency. The receiver includes a mixer-IF stage with the IF output phase locked to a reference frequency so that the absolute time delay through the IF stage is stabilized. The signal is then frequency demodulated, and the modulation signal is extracted by a narrow bandpass commutating filter. The phase of the modulation signal is then compared to the phase of the signal controlling one of the variable attenuators to produce a direction indication proportional thereto.

REFERENCES:
patent: 3121871 (1964-02-01), Beukers
patent: 3503071 (1970-03-01), Earp
patent: 3806930 (1974-04-01), Gobert

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