Design and Analysis of MEMS Varactor for Ka Band Applications

Abstract

AbstractA variable MEMS capacitor for Ka band frequency is designed having high capacitance ratio, less pull-in voltage, less stress misses, and better quality factor. MEMS varactor can be used as a tuning device to tune the frequency of a resonator. MEMS varactor is placed over the Substrate-Integrated Waveguide (SIW)-based resonator. The SIW resonator is designed over a single-layered Rogers RT/Duroid 6002 having dielectric constant \(\varepsilon_{r}\) = 2.94 and tanδ = 0.0012 whose substrate thickness is of 508 μm. The gap between SIW top layer and MEMS structure is 3 μm. MEMS varactor structures with holes and without holes are simulated. Meanders are used to support the membrane, which makes displacement more uniform. The serpentine-structured meanders are suitable as it decreases the pull-in voltage. Pull-in voltage of 0.84 V is achieved. The RF behavior of the MEMS variable capacitor depends on UP and DOWN capacitance and air gap between the two plates. The UP capacitance of 3.69 pF and resonance frequency of 39.5 kHz were achieved. When DC voltage is applied to the bottom fixed plate, the DOWN capacitance increases to 166.59 pF. A high Capacitance ratio of 45.14 is achieved. RF analysis of the device is done at 1–40 GHz. Return loss is noted as − 12.21 dB at 27 GHz. The low insertion loss of − 1.97 dB at 27 GHz for the proposed MEMS varactor has made the design suitable for the Ka communication band. This device is first of its kind in the Ka band communication where a minor change in structural parameters will have a huge impact over the response.KeywordsRF MEMS varactorSIWPull-in voltageInsertion loss