Passivation of miniature microwave coplanar waveguides using a thin film fluoropolymer electret

The insertion losses of miniature gold/silicon-on-insulator (SOI) coplanar waveguides (CPW) are rendered low, stable, and light insensitive when covered with a thin film (95 nm) fluoropolymer deposited by a trifluoromethane (CHF3) plasma. Microwave characterization (0–50 GHz) of the CPWs indicates that the fluoropolymer stabilizes a hydrogen-passivated silicon surface between the CPW tracks. The hydrophobic nature of the fluoropolymer acts as a humidity barrier, meaning that the underlying intertrack silicon surfaces do not re-oxidize over time—something that is known to increase losses. In addition, the fluoropolymer thin film also renders the CPW insertion losses insensitive to illumination with white light (2400 lx)—something potentially advantageous when using optical microscopy observations during microwave measurements. Capacitance–voltage (CV) measurements of gold/fluoropolymer/silicon metal–insulator-semiconductor (MIS) capacitors indicate that the fluoropolymer is an electret—storing positive charge. The experimental results suggest that the stored positive charge in the fluoropolymer electret and charge trapping influence surface-associated losses in CPW—MIS device modelling supports this. Finally, and on a practical note, the thin fluoropolymer film is easily pierced by commercial microwave probes and does not adhere to them—facilitating the repeatable and reproducible characterization of microwave electronic circuitry passivated by thin fluoropolymer.

Design and Analysis of a Non-Uniform Meander RF MEMS Switch

This paper aimed to design and analysis of non-uniform meander capacitive shunt RF MEMS switch. The less pull in voltage is obtained in flexure type membrane by proposed RF MEMS Switch. The selection of materials for the beam and dielectric layer is expressed in this paper and also shown the performance depends on materials utilized for the design. The high isolation of -31.15dB actuating at the pull-in voltage of 7.69V with a spring constant of 3.28N/m produced the switch and is obtained by the optimization process. Capacitive contact switches have capability of power handling. The actuated switch state provides an excellent isolation. It shorts the ground by RF signal. MEMS technology is the integration of electrical and mechanical components on single platform i.e. substrate [10]. From the literature, various researchers have proposed different RF MEMS Switch, but still there few challenges on optimization of the Switch for best performance. The electromechanical analysis such as Upstate, Downstate capacitances and stress analysis have been carried out. The performance of the switch is analyzed by taking appropriate materials selected by Ashby’s approach. These optimized dimensions are feasible to fabricate. The substrate height, material for the substrate and coplanar waveguides are used for the impendence matching. For obtaining the less pull in voltage overlapping area is to be increased.

Compact Double Notch Coplanar and Microstrip Bandstop Filters Using Metamaterial—Inspired Open Ring Resonators

Compact double notch coplanar and microstrip bandstop filters are described. They are based on a version of the open interconnected split ring resonator (OISRR) integrated in microstrip or coplanar waveguides. The OISRR introduces an RLC resonator connected in parallel with the propagating microstrip line. Therefore, this resonator can be modeled as a shunt circuit to ground, with the R, L and C elements connected in series. The consequence for the frequency response of the device is a notch band at the resonant frequency of the RLC shunt circuit. The number of notch bands can be controlled by adding more OISRRs, since each pair of rings can be modeled as a shunt circuit and therefore introduces an additional notch band. In this paper, we demonstrate that these additional rings can be introduced in a concentric way in the same cell, so the size of the device does not increase and a compact multi-notch bandstop response is achieved, with the same number of notch bands as pairs of concentric rings, plus an additional spurious band at a higher frequency.