Abstract: This invention is directed to a method for estimating and compensating for multipath errors in a pseudorandom noise ranging receiver. The method exploits the asymmetry of the correlation function and proportionately relates it to the magnitude of multipath error. In a pseudorandom noise ranging receiver, the correlation function is obtained by generating the local pseudorandom noise sequences at different programmed non-uniform phases resulting in non-uniformly spaced correlators. Numerically controlled oscillators, code generators and shift registers are programmed to determine the correlation values at non-uniformly distributed points on a correlation function. Curve fitting is undertaken to determine the code phase at which the correlation function peaks. A proportionality constant is applied to the measure of asymmetry of the correlation function to determine the multipath error in the pseudorandom noise signal. A filter is used to detect and eliminate outliers.

Abstract: A method for acquisition of a weak signal from a satellite in the presence of a strong interfering signal from another satellite is disclosed. The method encompasses identifying the auto-correlation peak due to the weak satellite signal from the cross correlation peaks due to the strong satellite signal. This invention presents a method and apparatus of acquiring a weak satellite signal in the presence of a strong interfering satellite signal in a receiver by two techniques, namely, the millisecond boundary correlation histogram method, and the frequency response correlation histogram method. Both the techniques distinguish between the correlation characteristics for auto-correlation and cross-correlation. The apparatus presented in the invention implements the methods of weak satellite signal acquisition in presence of a strong interfering satellite signal in a pseudorandom noise (PRN) receiver.