An RFMEMS based reflection type C-Ku band tunable band pass filter

In this paper, we present a novel band reflection type C-Ku band tunable band pass filter (BPF), which has been developed by surface micromachining technology for wireless applications. Our BPF consists of two identical band rejection filters (BRF) and a coplanar waveguide (CPW) 90-degree hybrid coupler. The BRF is composed of metal contact type RFMEMS switches, inductors and capacitors. In the fabrication, a sacrificial layer is applied to not only RFMEMS switch but also inductor, capacitor and CPW 90-degree hybrid coupler to form air bridge, short avoidable structure and enhanced capacitive coupling, respectively. Each tuning state in C- to Ku-band is achieved by RFMEMS switch operation, which selects adequate capacitors or inductors designed corresponding to each tuning state. The insertion losses of the BPF were 3.2 dB, 3.6 dB and 3.5 dB at 8 GHz, 12 GHz and 16 GHz, respectively.