Heikki Nieminen

Design of a temperature-stable RF MEM capacitor

This paper presents a novel temperature-compensated two-state microelectromechanical (MEM) capacitor. The principle to minimize temperature dependence is based on geometrical compensation and can be extended to other devices such as MEM varactors. The compensation structure eliminates the effect of intrinsic and thermal stress on device operation. This leads to a temperature-stable device without compromising the quality factor (Q) or the voltage behavior. The compensation structure increases the robustness of the devices, but does not require any modifications to the process. Measurement results verify that the OFF and ON capacitance change is less than 6% and the pull-in voltage is less than 5% when the temperature is varied from -30 to +70/spl deg/C.

Microelectromechanical capacitors for RF applications

This paper describes the design principles of electrostatically actuated microelectromechanical capacitors. Key properties, such as capacitance tuning range, quality factor (Q), different control methods, thermal stability, effect of radio frequency signal on capacitance and gas damping are examined. Experimental devices were designed and fabricated using the design principles. The two-gap capacitor has a measured nominal capacitance of 1.58 pF and achieves a tuning range of 2.25:1 with parasitics. When all parasitic capacitances to the substrate are extracted the measured nominal capacitance is 1.15 pF and the tuning range is 2.71:1. The device is made of electroplated gold and has a Q of 66 at 1 GHz, and 53 at 2 GHz. In addition, two- and three-state capacitors were designed, fabricated and characterized.

Microreplicated RF toroidal inductor

This paper reports on the modeling and fabrication of a truly three-dimensional high-quality-factor toroidal inductor using polymer replication processes. The critical dimensions are in the micrometer range, and the applied manufacturing method is based on polymer replication. Electrical measurements show that the inductor with an inductance of 6.0 nH exhibits a peak quality factor of 50 at a frequency of 3 GHz. Model verified by the measurement results shows that further improvement is still possible. Furthermore, the applied manufacturing technique can be extended to become a flexible packaging platform.

Gas damping model for a RF MEM switch and its dynamic characteristics

A compact model for a capacitive RF MEM switch with damping is presented. The damping model is based on analytic expressions for flow resistances due to the rarefied air flow in the gap and in the perforation holes. The complete switch model is constructed of elements resulting from the discretization of the beam deflection equation and has been implemented as a nonlinear electrical equivalent circuit. The model reproduces the beam displacement accurately. Comparison with measured transient on/off capacitance characteristics shows very good agreement.