Low Loss K-Band Tunable Bandpass Filter Using Micromachined Variable Capacitors

摘要

In this paper, a low loss K-band tunable bandpass filter with micromachined variable capacitors has been designed and fabricated, and its electrical performances have been measured. All elements of the tunable filter were fabricated using a surface micromachining technology and subsequent releasing process. The fabricated chip size was 2.75 mm × 1 mm. The measured initial center frequency was 20.7 GHz with a low insertion loss of 2.2 dB. In analog operating region of the capacitor, center frequency could be tuned from 20.7 to 18 GHz, which means the tuning-ratio of 13%. The maximum analog-mode capacitance ratio is 1.31 with an actuation voltage of 35 V. With the bias voltage of 60 V, the membrane was collapse to the bottom electrode and the center frequency was changed to 15.5 GHz, thus the tuning ratio is 25%. In this case, the capacitance ratio was calculated to be 1.9.