GNSS navigation system has a shortage—the satellite navigation signal is vulnerable to various interferences and thus leads to losses in performance of received signal. Wideband interference is common oppressive which impact on the receiver performance badly. In this paper, aiming at the linear frequency modulation (LFM) wideband interference, a new interference suppression method based on NEW-MDCFT is presented, and the model and implementation method of the suppression algorithm have been introduced. By adding the LFM jamming to the COMPASS B1 signal, the interference suppression method is simulated, and time domain performance, frequency domain performance, acquisition performance and tracking performance of the signal before and after interference suppression have been given. The results indicate that, the suppression method based on NEW-MDCFT has good LFM interference suppression performance and is able to perform good interference suppression in seriously-interfered environment.
Low frequency time-code timing service is an important mode in the modern timing system. Low frequency time-code timing radio station (BPC) is built by National Time Service Center in China. Based on the modern signal characteristic of BPC, a new timing method based on frequency sharing is presented, which is the additional spread spectrum modulation timing method in idle carrier wave of BPC. The rationale of the additional spread spectrum modulation timing method in BPC is researched. The performance of the method is analyzed. The research results indicate that the coverage of low frequency signal can be enlarged by the additional spread spectrum modulation timing method, and the timing precision of BPC will be enhanced. So low frequency time-code timing service can be used broadly.
Multipath error is an important error source in the tracking measurement of the navigation signals, and the multipath analysis is also significant to the signal system designing and signal optimizing. The multipath error envelope curve and average multipath error based on non-coherent EMLP (Early Minus Late Power) are usually used to measure the multipath rejection ability of the navigation signals. Now, the signal parameters of COMPASS satellite navigation system have been published. The method and principle to analyzing multipath error are given in this paper, the multipath performance of different signals adopted by COMPASS system is analyzed, and the simulation results are given. The analysis results in this paper can offer the research basic and reference to the system designing of the satellite navigation in our country.