A Compact Microstrip Patch Antenna for Civilian GPS Interference Mitigation

A compact microstrip patch antenna with an overall diameter of 6.4 cm (0.34 λ) at the global positioning system L1 band, capable of suppressing up to three radio frequency interferers (RFI) for civilian applications is presented. The antenna consists of two concentric annular rings, where the inner ring is excited at the dominant TM
₁₁
mode and the outer ring is excited at the TM
₂₁
mode. Both orthogonal polarizations of both modes are deployed to acquire a total of 3 degrees of freedom for nulling up to three interferers. The input and radiation parameters of the antenna are fully characterized through simulation and measurement. Also, using its measured two-dimensional gain patterns, the nulling performance in the presence of RFI is studied using a simple adaptive algorithm.