Analysis Methods of Linear Distortion Characteristics for GNSS Signals

Abstract

The non-ideality of payload channel can cause the navigation signal distortions, which would lead to the performance degradation. The distortions due to non-ideal channel fall into the linear and nonlinear signal distortions. The linear distortion is usually introduced by filter and triplexer, and non-linear distortion mainly depends on high power amplifier. Analyzing the non-ideal characteristics of channel is helpful to optimize the navigation payload design and improve the navigation signal quality. This paper only focuses on the analysis of linear distortion characteristics. The linear distortion characteristics include the amplitude-frequency characteristic and group delay characteristic. The non-ideality of amplitude-frequency characteristic can result in the distortion of signal frequency spectrum and power loss. The non-ideality of group delay characteristic can lead to the distortion of correlation function, and then introduce ranging bias error. This paper firstly presents the analysis methods from the view of correlation-domain and time-domain. The correlation-domain method exploits the real correlation function and ideal correlation function to obtain directly linear distortion characteristics. The time-domain method needs to recover the baseband waveform with the periodicity of short code signal component, and generate approximately the linear distortion characteristics using a FIR filter. Then, taking BPSK signals as an example, the performance of above two methods is studied by simulation.