The problems are described which the practicing engineer encounters who unwittingly approaches the realization of IIR digital filters for the first time. It is assumed that suitable design programs are available to calculate the coefficients, and it is desired only to implement the filter. Elegant solutions are provided for some of the most intimidating problems typically encountered, which are 1) input scaling requirements, 2) truncation noise propagation and recirculation, and 3) accurate low critical frequency filtering. It is shown that the direct form I noncanonic topology is the best for use in digital filtering, and while 16/32-bit DSP chips such as the TMS32010 or the ADSP-2100 can be used in many applications of high-fidelity digital audio, they will not meet the most demanding requirements.
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