Method and apparatus for code synchronization in a global positi

Details Method and apparatus for code synchronization in a global positi Method and apparatus for code synchronization in a global positi

1995-05-24

2000-02-08

Pham, Chi H.

Pulse or digital communications

Repeaters

Testing

375343, H04B 1500, H04K 100, H04L 2730

Patent

active

06023489&

ABSTRACT:
An improved method and apparatus for effecting code synchronization in a global positioning system receiver is disclosed herein. Within the receiver, digital in-phase (I) and quadrature (Q) samples of a plurality of received pseudorandom noise (PRN) encoded signals are provided to a code synchronization circuit. The code synchronization circuit is designed for coherent-mode operation when the receiver has achieved phase-lock with one of the PRN encoded signals, and operates in a non-coherent mode otherwise.
The code synchronization circuit includes an I-channel correlator for producing a coherent-mode discrimination signal by correlating in-phase (I) samples of a first of said PRN encoded signals with a discrimination pattern, wherein the first PRN encoded signal is encoded with a first PRN code. The discrimination pattern is comprised of two or more PRN code modulation components, the phases of which are adjusted based on the value of a code phase control signal obtained by averaging or otherwise processing the coherent-mode discrimination signal.
During non-coherent mode operation, both the in-phase (I) and quadrature (Q) samples of one of the PRN-encoded signals are correlated with a discrimination pattern and with a locally-generated replica of the PRN code. The results of the two I-channel correlations are then multiplied, as are the results of the Q-channel correlations. The resultant product signals generated during the multiplications are then combined into a non-coherent mode discrimination signal.

REFERENCES:
patent: 4649549 (1987-03-01), Halpern et al.
patent: 4894842 (1990-01-01), Broekhoven et al.
patent: 5414729 (1995-05-01), Fenton

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