A Fully Integrated Digital Microwave Tunable Filter Module Enabling Both the Center Frequency and Bandwidth Tuning

This paper describes a fully integrated 8-bit digital tunable filter module operating in the S band region and featuring a low insertion loss of less than 3.2 dB and small size of 3.6 mm by 4.7 mm. The tunable filter is based on a novel filter circuit includes three LC resonators that are connected to a T-network with a capacitive coupling between in and out terminal to form transmission zeros at both the upper and lower bandwidth limits. The filter circuit, 6 MEMS switches and a CMOS driving IC are integrated together into a single module by a newly developed 3D heterogeneous integration method. By switching the capacitor banks Cc, C1, C2 and Cm, 44% center frequency tuning and 115% bandwidth tuning has been achieved.