A new method in FIR filter design
Recently a method in FIR filter design using cosine modulation was proposed. Given a prototype M-th band lowpass filter with cutoff frequency at /spl tau//M, one can obtain a new filter with comparable frequency characteristics with rational cutoff frequency. In this paper, we extend the theory to the case of arbitrary cutoff frequency. The resulting method corresponds to finding the equivalent window impulse response which generates the filters. Simulation result shows that passband ripple, stopband attenuation, and transition bandwidth of the resulting filter are approximately the same as those in the original one. The quantization effect is also discussed.