Optimal STAP algorithms to GNSS receivers

Abstract

The use of SpaceTime Adaptive Processing (STAP) algorithms to mitigate the detrimental effects of jamming upon Global Navigation by Satellite Systems (GNSS) receivers has gained significant interest in the signal processing community. In this paper, we consider STAP as an enhancement to conventional spaceonly Controlled Radiation Pattern Antennas (CRPA) for GNSS applications. We found that accurately characterizing the antijamming performances requires to model together the STAP filter and the receiver correlator. We first show that the array output Signal to Noise plus Interference Ratio (SINR) is not an appropriate criterion to characterize STAP performances in the GNSS context, one have to consider the STAPpluscorrelator output SINR. Then, by analyzing the post correlation noise power, we derive a close form expression of the STAPpluscorrelator SINR, which allowed us to derive the optimal temporal constraint and a simplified version. These constraints may be used with space constraints either to steer beams or form nulls. Their robustness to linear technological defects is also studied. We point out that the processors based on this criterion allow restoring the defects and interference free performances within a 5 dB margin. Finally, the simplified processor is the preferred one: it exhibits good interference cancellation capacities in presence of technological defects, and requires neither any hybridization with the receiver nor prior knowledge of the received modulation; moreover it can be used both with BPSK and BOC modulation waveforms.