ABSTRACT
Impulse invariance method and bilinear transform method are the most common methods in the digital filter design.
The impulse invariance method is based on the idea that that we can design a digital filter whose time-domain impulse response is a sampled version of the impulse response of a continuous analog filter. Because the impulse responses of time-domain and frequency-domain are one-to-one correspondence, matching the impulse response can be matched to the frequency response. However, convert a time-domain impulse response to the frequency domain, it will become infinite bandwidth. So it’s easy to cause spectrum aliasing if we use the method to design filter.
