The experimental pattern behavior of a four-element adaptive array based on a steepest-descent feedback algorithm is described. The array uses four multiturn loop elements on an aircraft fuselage mock-up. Operational patterns have been measured as a function of various parameters: frequency, element placement, desired signal and interference angles of arrival, signal powers, etc. Typical patterns are presented and the performance characteristics of the array are described.

An experimental four-element adaptive array

: Adaptive filtering is a technique for optimizing the doppler filter response in an MTI (moving target indication) radar. In airborne MTI radars, the clutter spectrum is continually changing and varies with scan angle, antenna pattern, and angular distribution of the clutter intensity. Rain backscatter, if present, has a doppler spectrum which depends on local wind velocity and wind shear. An adaptive filter senses each of these effects and adaptively controls the filter weights to maximize the signal-to-clutter ratio in the filter output. Curves are presented in this report which illustrate the performance of adaptive filters in AMTI radar. The steady-state and transient response of adaptive filters, and performance in rain, are included. Methods of simplifying adaptive filter control loops are discussed. (Author)

Lawrence E. Brennan

Papers

Adaptive Filtering in AMTI Radar.