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This paper presents high-performance RF microelectromechanical systems (RF MEMS) tunable filters with constant absolute bandwidth for the 1.5-2.5-GHz wireless band. The filter design is based on corrugated coupled lines and ceramic substrates (εr=9.9) for miniaturization, and the 3-bit tuning network is fabricated using a digital/analog RF-MEMS device so as to provide a large capacitance ratio and continuous frequency coverage. Narrowband (72 ± 3 MHz) and wideband (115 ± 10 MHz) 1-dB bandwidth two-pole filters result in a measured insertion loss of 1.9-2.2 dB at 1.5-2.5 GHz with a power handling of 25 dBm and an IIP3 >> 33 dBm. The filters also showed no distortion when tested under wideband CDMA waveforms up to 24.8 dBm. The designs can be scaled to higher dielectric-constant substrates to result in smaller filters. To our knowledge, these filters represent the state-of-the-art at this frequency range using any planar tuning technology.
Microwave Theory and Techniques, IEEE Transactions on (Volume:58 , Issue: 6 )
Date of Publication: June 2010