Adaptive forms of the complex digital inverse filter

Two adaptive forms of the Complex Digital Inverse Filter (CDIF) for application in the rejection of narrowband interference are presented. The first form is a recursive LMS algorithm that updates the complex weights on a tapped delay line at every iteration. The second form is a recursive matrix inversion process - based on Robinson´s method - which allows solving for the optimum weights via a recursion process once the delay line correlation coefficients are determined. Convergence characteristics for the two forms are demonstrated and compared for a narrowband, band-pass input plus uncorrelated noise at each tap.