400–560 MHz Tunable 2-Pole RF MEMS Bandpass Filter with Improved Stopband Rejection

This paper presents a 400-560 MHz two-pole tunable filter with improved stopband rejection. In this design, commercial RF MEMS capacitors are used to tune center frequency and conduct passband matching. The RF MEMS capacitors are fully packaged using a 0.18 um COMS standard process with RFFE logic control, and have excellent reliability in the hundreds of billions of cycles. Air-core inductors are connected with RF MEMS capacitors to form high-Q LC tank. The measured insertion loss and 1-dB fractional bandwidth are less than 2.3 dB and 22-29 MHz, respectively. The stopband rejection is higher than 50 dB up to 2.0 GHz. The measured IIP3 is 35-42 dBm at all tuning frequencies. Application areas are for airborne and terrestrial communication systems in the UHF band in high congested environments.