False reacquisition mitigation in high sensitivity navigational satellite signal receivers
First Claim
1. A method for reacquisition of signals in a global satellite navigation receiver, the method comprising:
- collecting, for each carrier frequency and PN code phase dwell within a selected frequency range and selected code phase range, a sequence of correlation values derived from signals originating from a navigational satellite;
declaring a valid reacquisition at a selected dwell if a maximum power of the selected dwell exceeds a pre-determined high threshold value;
declaring a valid reacquisition at the selected dwell if the maximum power of the selected dwell is below the predetermined high threshold value, the maximum power of the selected dwell is above a pre-determined low threshold value, and the maximum power of the selected dwell is above a maximum power of all other dwells in the selected frequency range and selected code phase range.
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Accused Products
Abstract
The techniques to detect and mitigate the false reacquisition in a global satellite navigation receiver are disclosed. The false reacquisition due to frequency side-lobes and code autocorrelation secondary lobes are considered for mitigation. A set of two threshold values is used to detect correct reacquisition and reject false reacquisition. While the reacquisition of the signal is straight forward when the correlation is clear with the power above the first threshold, it is not so clear when the power is between two thresholds. So a further search for the maximum power among the retained dwells results in correct reacquisition. The search range depends upon the signal blockage interval and receiver dynamics. The feedback from navigational solution may be used to determine the search range both in frequency and code phase. In the case of frequency side-lobes, which occur only at specified frequency components, these frequencies are tested for maximum power response. The code side-lobes have similar characteristics and can be distinguished by the actual peak.
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Citations
34 Claims
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1. A method for reacquisition of signals in a global satellite navigation receiver, the method comprising:
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collecting, for each carrier frequency and PN code phase dwell within a selected frequency range and selected code phase range, a sequence of correlation values derived from signals originating from a navigational satellite;
declaring a valid reacquisition at a selected dwell if a maximum power of the selected dwell exceeds a pre-determined high threshold value;
declaring a valid reacquisition at the selected dwell if the maximum power of the selected dwell is below the predetermined high threshold value, the maximum power of the selected dwell is above a pre-determined low threshold value, and the maximum power of the selected dwell is above a maximum power of all other dwells in the selected frequency range and selected code phase range. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A global satellite navigation receiver device comprising an RF front end for receiving signals originating from navigation satellites, a baseband section receiving IF signals from the RF front end and generating one-millisecond correlation values, and a processor receiving correlation values from the baseband section, wherein the processor performs reacquisition of signals by:
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collecting, for each carrier frequency and PN code phase dwell within a selected frequency range and selected code phase range, a sequence of correlation values derived from signals originating from a navigational satellite;
declaring a valid reacquisition at a selected dwell if a maximum power of the selected dwell exceeds a pre-determined high threshold value;
declaring a valid reacquisition at the selected dwell if the maximum power of the selected dwell is below the predetermined high threshold value, the maximum power of the selected dwell is above a pre-determined low threshold value, and the maximum power of the selected dwell is above a maximum power of all other dwells in the selected frequency range and selected code phase range. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34)
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Specification