Adaptive space-time processing for interference suppression in phased array radar systems. II. Tracking radar

For pt.I see ibid., p.B8/1-B8/8 (2000). In phased array radar systems, a tracking process is performed using an electronic scan of a predetermined sector to provide a continuous information about the detected targets. In practice, the presence of interference (noise, clutter, and jamming signals) either prevent or deceive the tracking circuit to follow the real targets, and consequently, the tracking process is terminated. This paper presents an adaptive technique of filtering to suppress the interference in phased array tracking radar systems. The aim is to provide a key feature for discrimination between the desired and the interference signals. Unlike the time processing techniques, the present filtering process is based upon the target Doppler shift as well as the interference spatial distribution to suppress adaptively the undesired signals. This technique of filtering is referred to as adaptive coherent space-time (ACST) filter. The objectives are to investigate and evaluate in detail the performance of the adaptive filter under different interference environments. This includes total intercepted power, type and spatial distribution of the interference. The spatial covariance matrix of the interference is estimated using the direct matrix inversion (DMI) algorithm. Then the optimum Wiener solution for the adaptive filter is obtained. The results of our simulation show that an appreciable improvement in the signal to interference plus noise ratio at the filter's output "SINR/sub o/" is obtained. Also, the filter's performance is very sensitive to the interference type that has a direction either coincident with or close to the desired signal direction. In this case, a trade-off between the filter's complexity and the minimum SINR/sub o/ required for a continuous target tracking should be considered. In conclusion, the presented filter is an attractive and robust solution for solving the tracking problem of low target RCS immersed in interference (e.g., stealth aircraft).