The Design of Digital Notch Networks ror Use in Servomechanisms

The paper considers the design of narrow-band notch networks with low center frequencies for application in servomechanisms. The S-plane transfer function of a notch network is expressed in a form that allows the notch to be specified from measured data. The bilinear and matched Z transformation methods are used to derive a digital transfer function and it is shown that reliable results can be achieved by either method. The effects of the choice of sampling frequency are discussed along with frequency folding. A guide to sampling time selection is given.