Frequency and bandwidth tunable reliable MEMS bandpass filter for 24 GHz radar applications

Abstract

In this work, radio frequency (RF) micro-electromechanical system (MEMS)-based frequency and bandwidth tunable bandpass filter is presented for application in 24 GHz Doppler radar transceivers. The filter is fabricated on 635 μm alumina substrate using surface micromachining process. Total area of the filter is only 2.8 mm2 excluding bias lines and pads. Functional building blocks of the proposed filter are fabricated and tested independently to ensure optimum filter responses. The proposed filter can be tuned to any frequency between 22 and 24 GHz based on electrostatic actuations. It demonstrates insertion loss of 1.67 dB and matching of 18.6 dB at 24 GHz with fractional bandwidth of 6.5%. Filter gives acceptable matching over a 5 GHz bandwidth (21.65-26.65 GHz) with an average insertion loss of 4.7 dB. Filter works satisfactorily up to 10 billion cycles with 0.1 to 1 W of RF power. To the best of our knowledge, this is the first reported tunable MEMS bandpass filter at 24 GHz with 10 billion cycles reliability and with 1 W of RF power for radar applications.