Continuous Wave Interference Effects on Ranging Performance of Spread Spectrum Receivers

Abstract

Continuous wave interference (CWI) can induce significant ranging error for a spread spectrum receiver. Since both the spread spectrum signal and CWI are deterministic signals but truncated by the integrate and dump filters, deterministic signal models are built, and then their continuous frequency spectrums and specific signal forms in the processing flow are analyzed. This paper provides analytical expressions for code tracking performance of ranging receivers using coherent early minus late discriminators. The impacts of interference to signal power ratio (ISR), front-end bandwidth, integration time and early-late spacing on ranging bias are taken into account. According to the property of pseudo-random noise (PRN) code, the average magnitude of the code frequency spectrum is presented to investigate the general properties of ranging bias, and the magnitude fluctuations around the average are considered to analyze the properties of ranging bias with specific PRN codes. It is shown that the ranging bias induced by CWI depends on ISR, interference frequency, initial phases, code properties, receiver parameters, etc. Meanwhile, the envelope magnitude of the code frequency spectrum is provided for an easy way of estimating the upper bound of ranging bias. The 32 GPS C/A codes are taken as examples to show their worst cases of ranging performance under CWI.