An Inductive Link with Integrated Receiving Coil—Coupling Coefficient and Link Efficiency

Abstract

Inductive powering can free microelectromechanical systems (MEMS) devices from tethering to a power supply, thus expanding their scope of applications. We investigate inductive powering for MEMS using a microfabricated coil as a receiver operating at and below 1 MHz. The microcoil is designed to enclose the MEMS functions to achieve maximum coupling, and is built into a silicon substrate by our inlaid electroplating process, so that the microcoil has a small resistance despite its long trace. Non-negligible parasitic effects from the silicon substrate affect the characterization of an inductive link and its optimization. Taking into account the parasitic effects of Si microcoils, the coupling coefficient of the link is determined by a coil-model scheme that is different from conventional strategies. Furthermore, an equivalent circuit is developed for our link and used to analyze link operation over the frequency range of 4 kHz to 4 MHz. With measured link parameters, link efficiency is calculated with our equivalent circuit, and the results agree better with experiments than do conventional models. The equivalent circuit also indicates that microcoils with high quality factor at low frequencies, such as our inlaid electroplated coils, improve link performance, while parasitic capacitance has little effect.

A high contact force and high‐isolation radio‐frequency microelectromechanical systems switch for radio‐frequency front‐end applications

“…The contact resistance is represented as 33 : in the above equation, ρ is the resistivity of the material used in the contact area, R r belongs to resistive contamination of the contact area, H is the Meyer indentation hardness belongs to the material of the contact area (1.6 GPa for Au 34 ), and F c is the contact force. In our calculations, the Maxwell spreading resistance and Sharvin resistance do not qualitatively affect the analysis 35 .…”

“…The temperature of contact area based on the different power levels of input signal is plotted in Figure 15. As the contact material of the proposed switch is from Au (with softening temperature of 100°C 34 ), the switch has near ideal response and can handle high input signal powers without stiction.…”