Adaptive space-time processing for interference suppression in phased array radar systems. I. Search radar

This paper presents an adaptive technique of filtering to suppress the interference in phased array search radar systems. This interference includes noise, clutter, and jamming signals. Unlike the time processing techniques, our filtering process is based upon the target Doppler shift as well as the interference spatial distribution to suppress adaptively the undesired signals. This can be achieved by estimating the spatial covariance matrix of the interference using the direct matrix inversion (DMI) algorithm to compute the optimum weights of the adaptive filter. This technique of filtering is referred to as the adaptive coherent space-time (ACST) filter. A computer code has been developed to simulate the adaptive space-time filtering process. The objective is to investigate and evaluate in detail the performance of the adaptive filter under different interference environments including total intercepted power, statistical model, type and spatial distribution. The results of our simulation show that with moderate filter complexity an appreciable improvement in the signal to interference plus noise ratio at the filter's output "SINR" is obtained. In addition, the filter's performance is very sensitive to the interference type which has a direction either coincident with or close to the desired signal direction. The adaptive filter presented in this paper is an attractive and robust solution for solving the detection problem of low radar target cross section in an interference background such as stealth aircraft.