A 2-pole RF-MEMS tunable bandpass filter for high-power applications

This paper presents a novel type of tunable band-pass filters with constant bandwidth and wide tuning range. A constant absolute pass-band has been obtained by integrating a low-pass filter at the input and the output of the filter. The filter fabricated on duroid substrate can be tuned from 690MHz up to 1130MHz, by using RF-MEMS switches mounted in series with fixed capacitors. Matching is better than -12dB and the 3dB pass-band is 65MHz+/-5MHz. Measured insertion loss is less than 1.7dB at the upper end of the band and 3.3dB at the lower end. The filter shows no compression up to 1Watt of input power, and no measurable degradation of ACPR at the same power level.