High sensitivity and robustness carrier‐tracking loop for vehicular applications

Abstract

Global positioning system for vehicular applications in harsh urban environments faces some difficulties such as low signal intensity, intensive multipath and frequent signal blockage. These make it difficult to acquire and track signal normally by common receivers. This study proposes a high-sensitivity and high-robustness velocity tracking loop with inertial navigation system (INS) aiding. It joints the fast Fourier transform (FFT) results of all channels to estimate the velocity directly, called INS-aided joint FFT loop. Compared with conventional tracking loops, its sensitivity is improved effectively by jointing all channels in navigation domain. As this loop does not need to estimate the synchronisation parameters too, so it can avoid the influence of synchronisation parameter errors in single channel and achieve higher robustness. Simulation results show INS-aided JFFT loop has better performance in signal blockage, multipath and weak signal circumstances than some existing loops. An optimal carrier-tracking loop is also designed which combines INS-aided phase locked loop (PLL) and INS-aided JFFT. It can switch between INS-aided PLL and INS-aided JFFT by carrier-to-noise ratio (C/N 0) estimation to achieve the optimal performance when the signal strength changes.