The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 09, 1977
Filed:
Apr. 26, 1976
Paul R Norris, Issaquah, WA (US);
Other;
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.