Abstract
The performance of global navigation satellite system (GNSS) receivers is significantly affected by interference signals. For this reason, several research groups have proposed methods to mitigate the effect of different kinds of jammers. One effective method for wide-band interference mitigation (IM) is the high-rate DFT-based data manipulator (HDDM) pulse blanker (PB). It provides good performance to pulsed and frequency sparse interference. However, it and many other methods have poor performance against wide-band noise signals, which are not frequency-sparse. This article proposes to include automatic gain control (AGC) in the HDDM structure to attenuate the signal instead of removing it: the HDDM-AGC. It overcomes the wide-band noise limitation for IM at the cost of limiting mitigation capability to other signals. Previous studies with this approach were limited to only measuring the carrier-to-noise density ratio () performance of tracking, but this article extends the analysis to include the impact of the HDDM-AGC algorithm on the position, velocity, and time (PVT) solution. It allows an end-to-end evaluation and impact assessment of mitigation to a GNSS receiver. This study compares two commercial receivers: one high-end and one low-cost, with and without HDDM IM against laboratory-generated interference signals. The results show that the HDDM-AGC provides a PVT availability and precision comparable to high-end commercial receivers with integrated mitigation for most interference types. For pulse interferences, its performance is superior. Further, it is shown that degradation is minimized against wide-band noise interferences. Regarding low-cost receivers, the PVT availability can be increased up to 40% by applying an external HDDM-AGC.
Highlights
Interference mitigation is gaining importance in the research and development of global navigation satellite system (GNSS) receivers since incidents related to jammers are more and more frequent and are widely documented in the literature [1,2,3,4,5]
Simpler mitigation methods like a pulse blanker (PB) or a notch filter are ineffective against complex interference signals
The HE Roof antenna has a dip at the highest interference power, indicating that the RF splitter setup described in Figure 3 has limited isolation
Summary
Interference mitigation is gaining importance in the research and development of GNSS receivers since incidents related to jammers are more and more frequent and are widely documented in the literature [1,2,3,4,5]. Simpler mitigation methods like a PB or a notch filter are ineffective against complex interference signals. New GNSS signals present a higher complexity, typically associated with a larger bandwidth It makes the development of IM methods even more challenging. The fast Fourier transform (FFT) is calculated for every newly-received digital sample of the signal instead of a block of samples As a result, this oversampling increases the time selectivity and limit ringing and distortion effects. It uses a discrete Fourier transform (DFT)—or the more efficient FFT—to de-interleave a signal into multiple sub-bands. The PB provides temporal isolation and removal, and the DFT interleaving of the HDDM provides spectral isolation of an interference This approach is ideal for removing FMCW, which are sparse in the time-frequency domain.
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