Since the 1960s Digital Signal Processing (DSP) has been one of the most intensive fields of study in electronics. However, little has been produced specifically on linear non adaptive time variant digital filters. This is the first book to be dedicated to Time Variant Filtering. It provides a complete introduction to the theory and practice of one of the subclasses of time varying digital systems, parametric digital filters and oscillators. It presents many examples demonstrating the application of the techniques. It is an indispensable resource for professional engineers, researchers and PhD students involved in digital signal and image processing, as well as postgraduate students on courses in computer, electrical, electronic and similar departments.