A Switchable Bandpass Filter for Broadband, Dual-Band and Tri-Band Operations

In this brief, a novel microstrip switchable bandpass filter (BPF) is presented. By switching RF p-i-n diodes on/off, the proposed topology could provide three different filtering states: broadband bandpass filter (BBPF), dual-band bandpass filter (DBPF) and tri-band bandpass filter (TBPF). For each state, the relationship between bandwidths and return losses are newly analyzed by proposed algorithm, then the design charts can be easily summarized. In order to improve selectivity and stopband rejection, two cascaded proposed topologies are also considered and discussed briefly. For demonstration, two switchable circuits are designed, fabricated and measured in the experiment. Simulated and measured results are matched very well.