The extreme weakness of a global navigation satellitesystem (GNSS) signal makes it vulnerable to a widevariety of interfering signals, falling within the GNSSfrequency bands. Most of acquisition techniques usednow days are depends on Fast Fourier Transform (FFT).The FFT is numerically ill-posed method especially whennoise corrupts the signal extensively. Fast OrthogonalSearch (FOS) algorithm has been developed to acquirevery weak Global Positioning System (GPS)coarse/acquisition (C/A) signals in a software receiverinstead of FFT. Simulations indicate that the proposedmethod can acquire signal below signal-to-noise ratios(SNRs) below 25 dB. The percentage of improvement dueto use FOS instead of FFT is 18 % at low SNR.
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