A delayless subband adaptive filter using the projection method

Two topics associated with a delayless subband adaptive filter using the Hadamard transform are treated. One is to improve convergence speed and the other is to consider another aspect of subband adaptive filtering. Instead of LMS type algorithms which are often used in many applications, a projection method is employed as an adaptive algorithm to accelerate the convergence speed. The two filters corresponding to the secondary-path transfer function in an ANC system are included in the conversion rule from subband filters to a fullband filter. From this fact, a new structure which is similar to the conventional fullband filtered-X algorithm is derived. The increase of the convergence speed and the stability in steady state with these methods are demonstrated by computer simulations.