Interference Mitigation Using a Focal Plane Array

We consider the use of spatial filtering algorithms for radio frequency interference (RFI) mitigation in conjunction with a focal plane feed array of electrically small elements. Numerical simulations are used to study the performance of 7 and 19 element hexagonal dipole arrays with a 25 meter reflector at an operating frequency of 1612MHz. Using the maximum-SNR algorithm to generate array weights, an interfering signal was attenuated by 40 dB or more. The effective sensitivity of the system, including interferer power in the system noise temperature, was comparable to the sensitivity attained in the absence of RFI. Moving the interferer through the reflector pattern sidelobes caused fluctuations in the gain and system sensitivity. This effect was exacerbated by a reflector model with random surface distortions. These results indicate that array feeds are a promising approach for RFI migitation, but achieving stable radiation patterns in the presence of an interferer may require a tradeoff between pattern control and maximum attainable sensitivity.