Steering FIR notch filter adaption by initial coefficient control

Little mention is made of pitfalls or opportunities associated with initial conditions when adaptive filters are discussed, and it is nearly standard practice simply to impose zero initial conditions on the tap weights being adapted-without further ado. In the case of interference suppression in wideband signals by means of direct notch filtering this approach has been found inadequate to ensure convergence. However, utilizing a single non-zero initial tap value can not only bring about convergence, but also explicitly “steer” the phase condition of the resulting notch from minimum-phase to maximum-phase. It is also found that strong pattern sensitivity carries through from initial weights to final LMS filters, with zeroes lying on the z-plane unit circle being especially persistent shapers of the final notch filtering characteristics