[54] ENHANCED L1/L2 CODE CHANNEL FOR GLOBAL POSITIONING SYSTEM RECEIVERS
[75] Inventors: Leonard J. LaPadula, III, Carrollton;
John P. Volpi, Garland, both of Tex.;
Hugh L. Scott, Colorado Springs,
Colo.
[73] Assignee: Texas Instruments Incorporated,
Dallas, Tex.
[21] Appl. No.: 677,701
[22] Filed: Mar. 29,1991
[51] Int. Q.5 H04L 27/30
[52] U.S. a 375/1; 380/34;
342/357
[58] Field of Search 375/1; 380/34; 342/352,
342/356, 357
[56] References Cited
U.S. PATENT DOCUMENTS
4,468,793 8/1984 Johnson et al 375/97
4,485,383 11/1984 Maher 342/352
4,809,005 2/1989 Counselman, III 342/352
4,821,294 4/1989 Thomas, Jr 342/352 X
4,894,662 1/1990 Counselman 342/357
4,928,106 5/1990 Ashjaee et al 342/352
Primary Examiner—Bernarr E. Gregory
Attorney, Agent, or Firm—Rene E. Grossman; Richard
L. Donaldson
[57] ABSTRACT
An enhanced P-code channel (60) for use in a GPS receiver (10) to simultaneously track LI and L2 comprises a P-code clock generator (62) for generating two code clocks. The first code clock associates with LI and the second associates with L2. The code clocks have the same frequency but different phases from one another. Circuitry (64) and (66) generate and store a plurality of P-code chips. A first circuit (68,70) selects and updates P-code chips from the stored P-code chips that are in phase with the LI code clock. A second circuit (72 and 74) selects and updates P-code chips from the P-code chips and phased with the L2 code clock.
31 Claims, 4 Drawing Sheets
