Broadband power inversion array with maximally flat response at null directions

Abstract

The paper presents and investigates a new LMS based algorithm for a broadband power inversion array using tapped delay line processing. In this algorithm, the signals from each L-tap delay line are first transformed and separated into L/2 real-and-quadrature signals, with the ℓth signal determining the (ℓ-1)th derivative of the frequency response of the array. Rejection of jammers is then obtained by using the LMS algorithm to update the processing for the first transformed signals from all the array elements, while the processing for the other signals is adjusted to constrain the frequency response of the array to be maximally flat at the null directions. Since this latter adjustment needs to be performed only sparingly and the signal transformation is simple and straightforward, the complexity of the new algorithm is comparable to that when the LMS algorithm is used directly. However, because there is now only one group of real-and-quadrature signals that needs to be adaptively processed, the new algorithm can be significantly faster then the LMS algorithm.