A Bandpass Filter with Switched Active Networks

Abstract

Frequency selective networks play an important role in communications and instrumentation. As present-day techniques of miniaturization do not permit the use of inductors in filters, many alternative techniques of filter realization have become important. Of these, a digital filter like the N-path filter employing switched active networks is very useful for a variety of applications. With this in view, a project was initiated to develop a four-path bandpass filter using switched RC-active networks suitable for FDM use. The special features of this project are the standardization of digital and analogue circuits for repeatable use in the filter, and facilities for easy tuning. The important design features, fabrication and performance tests on the filter are described in this paper.