Time domain and realization of a class of digital hybrid filter

Abstract

AbstractThis paper describes a time‐domain design and realization of a digital hybrid filter with a specific cutoff frequency. The proposed realization is obtained by adding a single multiplier in a feedback loop to the low‐pass or high‐pass FIR filters with linear phase. The resulting hybrid filters can have the following improved frequency response: (1) Increased attenuation in the stop‐band (compared to that obtainable with a Kaiser windowed FIR filter of the same order) for the same transition bandwidth; (2) almost constant amplitude response in the stopband and no zero‐cross ripple; (3) no degradation of phase linearity in the pass‐band; and (4) almost constant phase response in the stopband. Also the hybrid filter designed and realized in this way is always stable and does not generate limit cycles. The time‐domain design and realization of digital hybrid filters of this class are introduced and a design example of a low‐pass hybrid filter is given.