A Reconfigurable Pseudohairpin Filter Based on MEMS Switches

This work presents a bandpass-reconfigurable planar pseudohairpin filter based on RF-MEMS switches. Hairpin-line structures are preferred to design microstrip filters because this class of filters offers a more compact size, and, in general, hairpin filters do not need ground connections for resonators. In this work, the U-shape resonators are arranged to obtain an interdigit capacitor to improve the coupling between the resonators. RF-MEMS switches modify the lengths of coupled resonators by adding microstrip segments to control the filter bandwidth, moving the center frequency and the return loss. An experimental hairpin tunable filter prototype based on RF-MEMS has been designed, fabricated, numerically and experimentally assessed, and compared concerning its tunability, quality factor, and capability with standard tunable filters based on PIN diodes. In conclusion, the tunable hairpin filter based on RF-MEMS switches offers the best performance in center frequency tuning range, compactness, and power consumption regarding reconfigurable filters based on standard PIN diodes switches. The obtained results are appealing and demonstrate the capabilities and potentialities of RF-MEMS to operate with the new communication standards that work at high microwave frequency bands.