A digitally controlled tunable N-path filter

A method based on the N-path principle is presented to design bandpass fiters tunable over a fairly wide tuning range. The design represents a compromise between the complexity of the switching waveform and that of the auxiliary output filter. Broad tuning range has been made possible by use of switched band-limiting networks. Experimental results verify the practicality of this approach. The system transfer function of a switched N-path filter with a very general switching waveform is derived and the results are applied to a variety of practical situations. The realization of this class of N-path filter using time-multiplexing of the basic analog network is discussed.