RF Filter Synthesis Based on Passively Coupled N-Path Resonators

N-path circuits, consisting of an array of switched capacitors driven with non-overlapping clocks, have been used to create radio frequency bandpass and band-stop filters. This paper covers a synthesizing methodology of RF bandpass filters (BPFs) that uses multiple passively coupled N-path resonators to realize a more selective transfer function with transmission zeros. Design details and measurement results of a proof-of-concept filter prototype with a 0.8-1.1-GHz tunable bandpass frequency realized in a 65-nm CMOS technology are presented.