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United States Patent | 4,457,006 |
Maine | June 26, 1984 |
In a Global Positioning System type of navigation system, a biphase modulated radio frequency input signal is applied to the "front end" of a double heterodyne receiver having a second intermediate frequency stage which operates in the audio frequency range. The audio output signal is phase locked to a 1 KHz reference signal and is applied to a microprocessor for processing via an interface circuit which includes a relatively simple amplitude detector and a novel biphase detector. The microprocessor also controls the phase shifting of a pseudorandom noise code generator whose output is modulated with the output of the first intermediate frequency stage of the receiver.
Inventors: | Maine; Reuben E. (Charlottesville, VA) |
Assignee: |
Sperry Corporation
(New York,
NY)
|
Appl. No.: | 06/321,945 |
Filed: | November 16, 1981 |
Current U.S. Class: | 375/333 ; 375/344; 455/264; 455/316 |
Current International Class: | G01S 5/14 (20060101); G01S 1/00 (20060101); H04L 027/06 () |
Field of Search: | 331/11,22,1R 375/1,83,87,97 455/257,261,264,265,316 |
3311832 | March 1967 | Schrader |
3623098 | November 1971 | Jones et al. |
4198604 | April 1980 | Holdaway |