MSE filter design and spectrum parameterization by orthogonal FAM transform

An orthonormal set of the frequency amplitude modulated (FAM) class of functions is used to produce a frequency domain FAM transform suitable for infinite impulse response (IIR) filter design with least squared error criterion. The orthonormal basis used is chosen to be effectively implemented by a set of identical second order allpass filters equipped with a common magnitude weighting. The allpass parameters (/spl theta/, r) are first adapted to the problem in order to get rapid convergence in the mean squared error (MSE). The results show that the new method produces IIR filters with the same or better (in MSE sense) frequency domain response than finite impulse response (FIR) filters with 5 to 7 times higher order. The method allows optimization of the group delay properties. There are three different ways to approximate linear phase characteristics in the IIR filters produced.<>