IEEE MTT-S 2008 International Microwave Symposium Technical Program

Session: WEP2C	RF MEMS Technology
Chair:	Daniela Staiculescu, Georgia Institute of Technology
Co-Chair:	Ronglin Li, Georgia Institute of Technology

WEP2C-01	Continuously Tunable RF-MEMS Varactor for High Power Applications
1237	S. Leidich¹, S. Kurth², T. Gessner², ¹Chemnitz University of Technology, Chemnitz, Germany, ²Fraunhofer IZM, Chemnitz, Germany
	A high power continuously tunable RF-MEMS capacitor (varactor) for frequencies from DC–4.0 GHz is presented. The device is specified for 0.8–1.6 pF analog tuning range and provides a Q factor of 100 for frequencies below 2.0 GHz. Using silicon bulk technology and wafer bonding techniques, RF and electrostatic actuation electrodes are arranged vertically. It enables controlled counteracting the attractive electrostatic forces generated by high RF signal amplitudes (self actuation). Using a time domain reflectometer based measurement setup and a resonating test circuit, stability against CW signals of up to 55 V rms has been shown. Due to the highly damped mechanical response, the capacitance setup is intrinsically insensitive to RF bursts (tp≤20 µs) of more than 120 V rms.

WEP2C-02	A 40/50 GHz diplexer realized with three dimensional copper micromachining
1516	J. R. Reid, D. Hanna, R. T. Webster, Air Force Research Laboratory, Hanscom AFB, United States
	This paper describes the design and measurement of a millimeter-wave (40/50GHz) diplexer fabricated using a three dimensional metal micromachining process. The measured diplexer has channels at 40.8 GHz and 51.1 GHz with fractional bandwidths of 2.36 GHz (5.8%) and 2.07 GHz (4.05%) and mid-band insertion loss of 1.58 dB and 3.52 dB, respectively. The diplexer measures 7.0 mm × 3.9 mm × 0.745 mm. It is fabricated from two comb line filters realized with microfabricated stripline resonators. The three-dimensional copper metal micromachining process utilized to fabricate the diplexer has demonstrated integration with active components and the diplexer is fabricated on wafer with a variety of other passive components.

WEP2C-03	Effect of Dielectric Film Thickness on Dielectric Charging of RF MEMS Capacitive Switches
1557	R. A. Daigler¹, G. Papaioannou², E. Papandreou², J. Papapolymerou¹, ¹Georgia Institute of Technology, Atlanta, United States, ²University of Athens, Athens, Greece
	For the first time, the effects of dielectric film thickness in the dielectric charging process of RF MEMS capacitive switches is presented. Both MEMS switches and MIM capacitors are used to investigate charging phenomena. The contribution of charge injection and dipole orientation has been identified. An empirical law that allows the prediction of stored charge on the film thickness was drawn. Above room temperature, the dependence of thermally stimulated depolarization current on a certain activation energy that is independent of dielectric film thickness allows the inclusion of this behavior in modeling tools.

WEP2C-04	Improved Distributed MEMS Matching Network for Low Frequency Applications Using a Slow-Wave Structure
1658	F. Domingue¹, A. B. Kouki¹, R. R. Mansour², ¹Ecole de technologie superieure, Montreal, Canada, ²University of Waterloo, Waterloo, Canada
	A reconfigurable impedance matching network has been developed for low frequency applications. The network is based on a distributed MEMS transmission line (DMTL) coupled with a slow-wave structure to reduce the physical length of the network by 25 % in comparison with a traditional DMTL. The proposed slow-wave structure (SW-DMTL) is studied in order to validate the integration possibilities and the improvements obtained. The SW-DMTL parameters are extracted from the electromagnetic simulation results and are used to design the SW-DMTL impedance tuner. The measured impedance coverage is presented and validates the potential of the proposed structure to realize a miniature DMTL matching network with a wide impedance coverage.

WEP2C-05	High-Q RF MEMS Capacitor with Digital/Analog Tuning Capabilities
1680	A. Grichener, B. Lakshminarayanan, G. M. Rebeiz, University of California, San Diego, La Jolla, United States
	This paper presents an RF MEMS switched-capacitor suitable for tunable filters and reconfigurable matching networks. The switched-capacitor contains design features that result in a tunable capacitance ratio of 5-7, a high-Q (greater than 100) at C to X-band frequencies, and excellent reliability performance. The switched-capacitor has been temperature cycled to 120 degrees Celcius with only a 3-4 V change in the pull-down voltage. The design also features a digital switched-capacitor mode and an analog tuning mode, making it ideal for precision tuning.

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