Mitigation of Continuous and Pulsed Radio Interference with GNSS Antenna Arrays

A number of antenna array techniques for radio interference mitigation in GNSS receivers have been intensively studied in the last two decades showing that space-only or space-time adaptive processing allows for significant improvements. These investigations were primarily focused on mitigation of continuous interference signals assumed to be of intentional nature in the “quiet” GPS L1 band. In contrast to the L1 band, new navigation signals of GPS/Galileo L5/E5 frequency band have to share the radio spectrum with several civil and military radar systems. In a single-antenna GNSS receiver, the pulsed interference originated from such radar systems is usually handled by using the pulse blanking or frequency extinction techniques. In an antenna array system, more efficient mitigation of pulsed interference can be obtained by adding the spatial domain to the signal processing. In this case, the GNSS antenna array receiver may be designed in a way that allows for simultaneous mitigation of continuous and pulsed interferers. In the paper the performance of two space-time adaptive processing (STAP) techniques has been investigated in interference scenarios with continuous and pulsed sources by using the simulations of a software multi-antenna receiver. It has been shown that the minimum variance distortionless response (MVDR) processor with a corresponding directional constrain delivers both a good performance in term of code and Doppler receiver tracking errors and minimal distortions of the useful GNSS signal. The second investigated STAP technique was minimum mean square error (MMSE) processor. The effect of the number of the STAP time-taps on the performance of the MVDR and MMSE processors has been shown. The combination of the adaptive array processing with the pulse blanking has been examined showing that the simple-to-implement pulse blanking can noticeably improve the overall performance in pulsed interference scenarios