Abstract:

A new code discriminator algorithm of maximum constrained generalized extended approximation(GEA) is proposed to meet the requirment of high precision phase discriminator for GNSS code tracking loop. The GEA model is developed based on correlation results of five correlators. Correlation value distribution function and then code phase difference are obtained by fitting the five correlation nodes. Mean while the maximum of correlation nodes is used to constrain the fitting, which can further improve the precesion and adaptability of code phase difference estimation. The new algorithm is compared with the common normalized earlyminuslate envelope(NEMLE) discriminator from three aspects: linear range, pullin range and phase discriminator error. Results of Monte Carlo simulation and tests of actual GPS sampling data on GPS software receiver platform show that the error performance of the GEA method combined with the maximum correlation node constraint which can effectively improve the precesion of code phase discriminator is greatly superior to that of the NEMLE discriminator.