Thesis Type: Postgraduate
Institution Of The Thesis: Orta Doğu Teknik Üniversitesi, Faculty of Engineering, Department of Electrical and Electronics Engineering, Turkey
Approval Date: 2010
Student: ÇAĞRI ÇETİNTEPE
Co-Supervisor: TAYFUN AKIN, ŞİMŞEK DEMİRAbstract:
This thesis presents development of microwave lumped elements for a specific surface-micromachining based technology, a self-contained mechanical characterization of fixed-fixed type beams and realization of a shunt, capacitive-contact RF MEMS switch for millimeter-wave applications. Interdigital capacitor, planar spiral inductor and microstrip patch lumped elements developed in this thesis are tailored for a surface-micromachining technology incorporating a single metallization layer, which allows an easy and low-cost fabrication process while permitting mass production. Utilizing these elements, a bandpass filter is fabricated monolithically with success, which exhibits a measured in-band return loss better than -20 dB and insertion loss of 1.2 dB, a pass-band located in S-band and a stop-band extending up to 20 GHz. Analytical derivations for deflection profile and spring constant of fixed-fixed beams are derived for constant distributed loads while taking axial effects into account. Having built experience with the mechanical domain, next, Finite Difference solution schemes are established for pre-pull-in and post-pull-in electrostatic actuation problems. Using the developed numerical tools; pull-in, release and zipping phenomena are investigated. In particular, semi-empirical expressions are developed for the pull-in voltage with associated errors not exceeding 3.7 % of FEA (Finite Element Analysis) results for typical configurations. The shunt, capacitive-contact RF MEMS switch is designed in electromagnetic and mechanical domains for Ka-band operation. Switches fabricated in the first process run could not meet the design specifications. After identifying sources of relevant discrepancies, a design modification is attempted and re-fabricated devices are operated successfully. In particular, measured OFF-state return and insertion losses better than -16.4 dB and 0.27 dB are attained in 1-40 GHz. By applying a 20-25V actuation, ON-state resonances are tuned precisely to 35 GHz with an optimum isolation level of 39 dB.