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Low insertion loss and high isolation capacitive RF MEMS switch with low pull-in voltage

journal contribution
posted on 2017-10-01, 00:00 authored by Y Mafinejad, Abbas KouzaniAbbas Kouzani, K Mafinezhad, R Hosseinnezhad
Micro electromechanical system (MEMS) shunt capacitive switches behave chiefly as a capacitor at both up and down states. Therefore, input-output matching for these switches is affected by varying the frequency. Although increasing the amount of capacitance at the up state reduces the actuation voltage, it deteriorates the RF parameters. This paper proposes a remedy for this problem in the form of two short high-impedance transmission lines (SHITLs) which are included at both ends of the MEMS switch. The SHITLs are implemented through adoption of a discontinued CPW transmission line. With this implementation, the switch can be modelled as a T circuit, neutralizing a capacitance behavior of MEMS switch at the up state. The paper also proposes an optimised fabrication process to realize a flat and planar bridge for the suggested RF MEMS switch. The measurement recorded by SEM and AFM shows that the proposed method significantly improves the planarity of the membrane. The RF and mechanical parameters of the fabricated switch are evaluated by Vector Network Analyser and Laser Doppler Vibrometer. At the up state, the switch has a return loss less than −20 dB in the entire frequency band (C-K). The isolation at the down state is better than 10 dB for the lower frequencies and increases to values better than 18 dB for the higher frequencies. The measured pull-in voltage is almost 20 V and the mechanical resonance frequency is 164 kHz.

History

Journal

International journal of advanced manufacturing technology

Volume

93

Pagination

661-670

Location

Berlin, Germany

ISSN

0268-3768

eISSN

1433-3015

Language

eng

Publication classification

C Journal article, C1 Refereed article in a scholarly journal

Copyright notice

2017, Springer-Verlag London

Issue

1-4

Publisher

Springer Verlag