Design of circularly symmetric two- and three-dimensional digital filters using the concept of the GIC

A realisation method for two-dimensional and three-dimensional rotated infinite-impulse response digital filters based on the concept of the generalised-immittance convertor is proposed. First, analogue reference networks realising first- and second-order transfer functions of rotated two-dimensional and three-dimensional filters are constructed; corresponding digital-filter structures are then derived from these networks using wave characterisation. The design method is simple since the digital-filter structures can be obtained directly from the transfer functions without realising the analogue reference networks. For first-order sections, the proposed digital-filter structures are canonic with respect to the number of multipliers and delays