A Coplanar Waveguide Bandwidth-Tunable Lowpass Filter With Broadband Rejection

A coplanar waveguide lowpass filter (CPW-LPF) with high bandwidth tunability and broadband rejection is demonstrated. Compared to the reported design approaches, a relatively straightforward design with varactor-tuned microwave resonators is proposed for the realization of the tunable CPW-LPF. It is shown that the presented tunable CPW-LPF has a wide bandwidth tuning range via a small bias swing, low passband insertion loss, as well as wideband rejection. Also, the filter roll-off remains unchanged while the cut-off frequency is varied. The proposed tunable CPW-LPF is experimentally verified and expected to find applications in modern communication systems.