Patent ID: 8542718

Claim:
A method for high-sensitivity GPS/GNSS signal acquisition and tracking in a stationary GPS/GNSS receiver including a front end section and a signal processing section, the front end section receiving a GPS/GNSS signal from satellites and producing a digitized complex baseband signal, the method comprising: selecting a known B-bit sequence of navigation data, the known B-bit sequence having a known navigation data bit pattern and containing an entire M-bit sequence shorter than the known B-bit sequence as part thereof; selecting a trial frequency f 0p for compensating apparent Doppler shift in the received signal; selecting a trial bit boundary location t 0s for determining navigation data bit boundaries of the received signal; performing a search process including: capturing an M-bit block of the baseband signal from the received signal using start time corresponding to the selected trial bit boundary location, the M-bit block including an M-bit sequence of the navigation data, the M-bit sequence being known to be contained in the known B-bit sequence; Doppler-compensating the M-bit block using the trial frequency f 0p ; partitioning the M-bit block into M successive sub-blocks each having a length of one navigation data bit; producing M compressed sample blocks by synchronous summation using a periodicity of one-period of C/A code, each compressed sample block having N-samples and a length of one period of C/A code; cross-correlating each of the M compressed sample blocks with N cyclic shifts of one period of reference C/A code for a selected satellite so as to produce an N-by-M correlation matrix, k th column of the correlation matrix consisting of N complex values of an N-value correlation function of the k th compressed sample block, K th row of the correlation matrix corresponding to M bits of the M-bit block at the K-l th cyclic shift; and data-shift correlating each row of the correlation matrix with a selected M-bit sequence within the known B-bit sequence by shifting the selected M-bit sequence from one end to the other of the known B-bit sequence so as to produce (B−M+1) data-shift correlation values for each row; and finding the data-shift correlation value having a maximum-magnitude MAG MAX and parameters associated therewith, by repeating the search process for predetermined combinations of the trial frequencies and the trial bit boundary locations, wherein the associated parameters includes: frequency f 0MAX indicating a measured apparent Doppler shift of the received signal; bit boundary location t 0MAX providing a bit boundary location of the captured M-bit sequence; a row index K MAX of the correlation matrix indicating a location of a code epoch of C/A code of the received signal; and an amount of shift J MAX of the selected M-bit sequence within the known B-bit sequence, the amount of shift indicating a location of a start bit of the captured M-bit sequence with respect to the known B-bit sequence.