ABSTRACT
Infinite impulse response (IIR) filters, also known as recursive filters, take advantage of the continuous-time filters made up of networks with discrete elements. Frequency transformations are available, and these transforms permit a low-pass filter design to be adapted to another low-pass filter, a high-pass filter, a band-pass filter, or a band-stop filter. In recursive IIR filters, the poles of the transfer function can be placed anywhere within the unit circle in the frequency plane. As a result, IIR filters can usually match physical systems well. It is left to the filter designer to decide on the various trade-offs between cost and precision in trying to reach a specified goal. The transformations do not produce identical results since the output of the continuous case is due to the convolution of input and filter through integration, whereas the digital case is a convolution performed by summation.
