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This paper reports a continuously tunable lumped bandpass filter implemented in a third-order coupled resonator configuration. The filter is fabricated on a Borosilicate glass substrate using a surface micromachining technology that offers hightunable passive components. Continuous electrostatic tuning is achieved using three tunable capacitor banks, each consisting of one continuously tunable capacitor and three switched capacitors with pull-in voltage of less than 40 V. The center frequency of the filter is tuned from 1 GHz down to 600 MHz while maintaining a 3-dB bandwidth of 13%-14% and insertion loss of less than 4 dB. The maximum group delay is less than 10 ns across the entire tuning range. The temperature stability of the center frequency from -50°C to 50°C is better than 2%. The measured tuning speed of the filter is better than 80 s, and the is better than 20 dBm, which are in good agreement with simulations. The filter occupies a small size of less than 1.5 cm × 1.1 cm. The implemented filter shows the highest performance amongst the fully integrated microelectromechanical systems filters operating at sub-gigahertz range.

This paper reports on the implementation of miniaturized ultra-wideband filters integrated with tunable notch filters using a silicon-based integrated passive device technology. An ultra-wideband bandpass filter is realized on a micromachined silicon substrate, showing an insertion loss of 1.1 dB, return loss of better than 15 dB, and attenuation of more than 30 dB at both lower and upper stop-bands, with a spurious-free response up to 40 GHz. The filter occupies only 2.9 mm 2.4 mm of die area. To address the in-band interference issues associated with ultra-wideband communication, very compact tunable notch filters are monolithically integrated with the bandpass filters. A two-pole tunable notch filter integrated with an ultra-wideband filter provides more than 20 dB rejection in the 5-6 GHz range to reject U-NII interferences, with a total footprint of 4.8 mm 2.9 mm. The power handling, linearity, and temperature stability of filters are characterized and presented in this paper.

This paper reports on micromachined tunable bandstop filters that exhibit an octave frequency tuning range with high stopband rejection and low out-of-band loss. In addition to continuous frequency tuning, stopband switch on-off capability is realized by employing ohmic switches along with tunable capacitors. The fully re-configurable filters in this work are fabricated using a silicon-based integrated passive device technology and are the smallest-size bandstop filters reported in the low SHF range.