Design of 2-D linear phase variable recursive digital filters for parallel form implementation

The magnitude and phase characteristics of digital filters are determined by the transfer function coefficients. These characteristics are often required to vary in real-time in the course of signal processing. This requirement can be achieved by filters with coefficients that are directly computable from the spectral parameters. Such filters are referred to as variable filters. An optimisation technique is proposed for the design of two-dimensional linear phase variable recursive digital filters using the parallel form. The variable coefficients are expressed as computable analytic functions of the spectral parameters defining the desired frequency response. Computer simulations show that the proposed approach can design an entire family of filters using just one variable filter structure. Examples are presented to illustrate the method.