Fast fourier transform with down sampling based navigational satellite signal tracking
First Claim
1. A method for tracking received signals in a global satellite navigation receiver, the method comprising:
- collecting a sequence of correlation values derived from the received signals correlated with PN codes;
partitioning the collected sequence into N groups of consecutive correlation values, where N is a positive integer;
calculating from each of the N groups, a corresponding set of N values forming a downsampled sequence;
converting the down-sampled sequence from time domain to frequency domain to produce a frequency domain sequence;
identifying a maximum power value in the frequency domain sequence;
calculating a frequency error between the received signals and a locally generated replica signal based on the identified maximum power value; and
adjusting a local replica carrier frequency by an amount equal to the frequency error.
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Accused Products
Abstract
A method and device to track navigational satellite signals, are claimed. In this invention, a combination of down-sampling and frequency domain transformation are used to track the navigational satellite signals under dynamic environment. A Fast Fourier Transform (FFT) with long coherent integration has been employed to determine the varying frequency components with high resolution. By representing a number of correlation values with their average value, it is possible to represent a long sequence of input values by a smaller number of values and a relatively short length FFT can reveal the low frequency components that are present in the signal during tracking operation. A large reduction in the computational load may be achieved using this down-sampling method without compromising on the frequency resolution.
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Citations
26 Claims
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1. A method for tracking received signals in a global satellite navigation receiver, the method comprising:
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collecting a sequence of correlation values derived from the received signals correlated with PN codes; partitioning the collected sequence into N groups of consecutive correlation values, where N is a positive integer; calculating from each of the N groups, a corresponding set of N values forming a downsampled sequence; converting the down-sampled sequence from time domain to frequency domain to produce a frequency domain sequence; identifying a maximum power value in the frequency domain sequence; calculating a frequency error between the received signals and a locally generated replica signal based on the identified maximum power value; and adjusting a local replica carrier frequency by an amount equal to the frequency error. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A global satellite navigation system receiver device comprising an RF front end for receiving signals from navigational satellites, a baseband section receiving IF signals from the RF front end, and a processor receiving I, Q correlation values from the baseband section, wherein the processor:
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collects a sequence of the correlation values derived from the received signals correlated with PN codes; partitions the collected sequence into N groups of consecutive correlation values, where N is a positive integer; calculates from each of the N groups, a corresponding set of N values forming a downsampled sequence; converts the down-sampled sequence from time domain to frequency domain to produce a frequency domain sequence; identifies a maximum power value in the frequency domain sequence; calculates a frequency error between the received signal and a locally generated signal based on the identified maximum power value; and adjusts a local replica carrier frequency by an amount equal to the frequency error. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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Specification