Split C/A code receiver
AssigneeNovAtel Inc.
InventorsPatrick C. Fenton, Albert J. Van Dierendonck
Life of this patent
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Abstract
A GPS receiver that acquires and tracks a split-C/A code separately aligns with the received signal the phases of a locally-generated 10.23 MHz square wave, which can be thought of as a 20.46 MHz square-wave code, and a locally-generated 1.023 MHz C/A code. The receiver first aligns the phase of the locally-generated square-wave code with the received signal, and tracks one of the multiple peaks of the split-C/A code autocorrelation function. It then shifts the phase of the locally-generated C/A code with respect to the phase of the locally-generated square-wave code, to align the local and the received C/A codes and position the correlators on the center peak of the split-C/A. The receiver then tracks the center peak directly, using a locally-generated split-C/A code.
Claims20
A GPS receiver for receiving split-C/A coded signals, the receiver including:
- A. a C/A code generator for generating a locally-generated C/A-code;
- B. a square-wave code generator for generating a locally-generated square-wave code;
- C. means for producing a locally-generated split-C/A code, said means digitally mixing the locally-generated C/A code and the locally-generated square-wave code;
- D. correlators for producing correlation measurements for use in:
- (i) synchronizing the locally-generated square-wave code with the square-wave code included in the received signal;
- (ii) synchronizing the locally-generated C/A code with the C/A code included in the received signal;
- and
- (iii) synchronizing the locally-generated split-C/A code with the split C/A code included in the received signal;
- and
- E. means for adjusting the phase of the square-wave code produced by the square-wave code generator in response to the correlation measurements associated with the locally-generated square-wave code;
- and
- F. means for adjusting the phase of the C/A code produced by the C/A code generator relative to the phase of the locally-generated square wave code in response to the correlation measurements associated with the locally-generated C/A code.
A method of synchronizing a locally-generated split-C/A code to a split-C/A code in a received signal, the method including the steps of:
- A. producing a locally-generated square-wave code and using early-minus-late correlation measurements associated with the locally-generated square-wave code to align the locally-generated square-wave code with the square-wave code in the received signal;
- B. removing the square-wave code from the received signal by multiplying the received signal by a punctual version of the locally-generated square-wave code;
- C. producing a locally-generated C/A code and usinig early-minus-late correlation measurements associated with the locally-generated C/A code to align the locally-generated C/A code with the C/A code in the received signal by shifting the phase of the locally-generated C/A code relative to the phase of the locally-generated square-wave code;
- and
- D. tracking the split-C/A code using early-minus-late correlation measurements associated with a locally-generated split-C/A code.
A method of synchronizing a locally-generated split-C/A code to a split-C/A code in a received signal, the method including the steps of:
- A. producing a locally-generated square-wave code and using early-minus-late correlation measurements associated with the locally-generated square-wave code to align the locally-generated square-wave code with the square-wave code in the received signal;
- B. shifting the phase of a locally-generated C/A code that is included in the locally-generated split-C/A code in accordance with early-minus-late correlation measurements associated with the locally-generated split-C/A code that are made at the locations of peaks in an autocorrelation function associated with the split-C/A code;
- and
- C. tracking the split-C/A code using early-minus-late correlation measurements associated with a locally-generated split-C/A code.
A GPS receiver for receiving split-C/A coded signals, the receiver including:
- A. a C/A code generator for generating a locally-generated C/A-code;
- B. a square-wave code generator for generating a locally-generated square-wave code;
- C. a multiplier for producing a locally-generated split-C/A code, the multiplier digitally mixing the locally-generated C/A code and the locally-generated square-wave code;
- D. correlators for producing correlation measurements for use in:
- (i) synchronizing the locally-generated square-wave code with the square-wave code included in the received signal;
- (ii) synchronizing the locally-generated C/A code with the C/A code included in the received signal;
- and
- (iii) synchronizing the locally-generated split-C/A code with the split C/A code included in the received signal;
- and
- E. a controller for
- i. adjusting the phase of the square-wave code produced by the square-wave code generator in response to the correlation measurements associated with the locally-generated square-wave code;
- and
- ii. adjusting the phase of the C/A code produced by the C/A code generator relative to the phase of the locally-generated square wave code in response to the correlation, measurements associated with the locally-generated C/A code.
Dependencies are inferred from the claim text.