Digital filter structures for canonic signed-digit code implementation by microprocessor

The effect of structure on microprocessor-based recursive digital filters which employ a predetermined multiplication technique based on the canonic signed-digit code is considered. It is shown that, by including structure as a parameter in the design of such filters, transfer-function coefficient quantisation error may be reduced. A set of design rules for choosing the best structure to implement a 2nd-order transfer function, which has pairs of zeros located at + 1 or ¿¿ 1 in the complex z-plane, is developed. These rules are applied to an 8th-order Chebyshev type bandpass filter, realised as a cascade of four 2nd-order sections by a microprocessor designed specifically for signal processing.