Abstract
Antenna array processing techniques are studied in GNSS as effective tools to mitigate interference in spatial and spatiotemporal domains. However, without specific considerations, the array processing results in biases and distortions in the cross-ambiguity function (CAF) of the ranging codes. Inspace-time processing (STP)the CAF misshaping can happen due to the combined effect of space-time processing and the unintentional signal attenuation by filtering. This paper focuses on characterizing these degradations for different controlled signal scenarios and for live data from an antenna array. The antenna array simulation method introduced in this paper enables one to perform accurate analyses in the field of STP. The effects of relative placement of the interference source with respect to the desired signal direction are shown using overall measurement errors and profile of the signal strength. Analyses of contributions from each source of distortion are conducted individually and collectively. Effects of distortions on GNSS pseudorange errors and position errors are compared forblind,semi-distortionless,anddistortionlessbeamforming methods. The results from characterization can be useful for designing low distortion filters that are especially important for high accuracy GNSS applications in challenging environments.
Highlights
Satellite based navigation systems are widely used for positioning and timing
The antenna array was mounted on the vehicle top (Figure 9(b)) and the radio frequency (RF) cables from the six antenna elements were connected to the phase coherent six-channel Fraunhofer/TeleOrbit RF frontend (Figure 9(c))
A theoretical analysis of the distortions observed in the GPS measurements due to antenna array processing was provided and supported with results from simulated and live signals, for different beamforming methods categorized as blind, semi-distortionless, and distortionless
Summary
Satellite based navigation systems are widely used for positioning and timing. Signals from different Global Navigation Satellite System (GNSS) constellations (e.g., GPS, GLONASS, which are globally operational; BeiDou, Galileo, which are scheduled to be fully operational; IRNSS, QZSS, which provide regional coverage) can offer increased accuracy, robustness, availability, and reliability [1]. Even though GNSS offers superior and diverse features, the position, velocity, and time (PVT) estimates provided by a receiver can degrade due to the presence of interfering signals. Interference affects primarily signal acquisition and tracking and degrades navigation parameter estimation. By using antenna arrays in GNSS receivers, the spatial and temporal characteristics of the incident signals can be exploited to mitigate interference. Research into antenna array-based methods for GNSS interference mitigation has begun several years ago. Further enhancement can be provided by including a Tapped Delay Line (TDL) behind each antenna element and by performing space-time processing (STP)
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