Transversal filter techniques for adaptive array applications

The performance of current cancellation systems is limited when broadband cancellation is required. The paper covers some of the work performed at Plessey (Roke Manor) to overcome these problems by using an adaptive transversal filter. The paper begins by considering some of the effects which limit broadband performance of current cancellation equipment. Secondly, assuming that each tap weighting of the transversal filter is controlled by a correlation loop, a matrix equation is derived for these weight values. From this the residual signal level can be found. The paper then explains the computer program used to solve the matrix equation for given input signal conditions. This result is then used to find the residual power. These evaluations show the potential improvement of an ATF cancellation system compared with a conventional system. Finally, practical work with a four-tap system is discussed, and an improved cancellation performance is demonstrated using low-cost cancellation loops.