A Class of Wide-Band Linear-Phase FIR Differentiators Using a Two-Rate Approach and the Frequency-Response Masking Technique

This paper introduces a class of wide-band linear-phase finite-length impulse response (FIR) differentiators. It is based on two-rate and frequency-response masking techniques. It is shown how to use these techniques to obtain all four types of linear-phase FIR differentiators. Design examples demonstrate that differentiators in this class can achieve substantial savings in arithmetic complexity in comparison with conventional direct-form linear-phase FIR differentiators. The savings achievable depend on the bandwidth and increase with increasing bandwidth beyond the break-even points which are in the neighborhood of 90% (80%) of the whole bandwidth for Type II and III (Type I and IV) differentiators. The price to pay for the savings is a moderate increase in the delay and number of delay elements. Further, in terms of structural arithmetic operations, the proposed filters are comparable to filters based on piecewise-polynomial impulse responses. The advantage of the proposed filters is that they can be implemented using non-recursive structures as opposed to the polynomial-based filters which are implemented with recursive structures.