Mutual coupling is an inevitable phenomenon in multiantenna systems, usually reducing the system performance. Numerous works have focused on the reduction of this effect. The aim is maintaining the mutual coupling suppressing structure as simple as possible while having a high amount of mutual coupling reduction. This letter presents a novel structure suppressing the mutual coupling between nearby patches. It is composed of only a simple U-shaped microstrip, which reduces the mutual coupling considerably. The structure has been constructed and tested. The measurement results prove the high efficiency of this configuration.

A closed-form inductance expression for compact modeling of integrated inductors is presented. The expression is more accurate than previously published closed formulas. Moreover, due to its physics-based nature, it is scalable. That is demonstrated by comparison with the measured inductance for a complete set of inductors with different layout parameters.

This paper gives a new insight into the problem of the irreversible stiction of RF microelectromechanical systems (MEMS) attributed to the dielectric charging. We present a model for the electrostatic actuation of MEMS devices taking into account the nonuniform distributions of the air gap and the charges in the dielectric layer. The major result of our study is the impossibility to invoke the sole uniform dielectric charging phenomenon to explain the irreversible stiction of electrostatic MEMS devices. In the absence of other forces, a nonzero variance of the charge distribution is required to explain the stiction of the device. Considering only uniform residual charge densities, previous reported works could only account for a drift of the actuation characteristics as a whole. In case of a uniform air-gap distribution, our analytical model can already account for an increase of the up-capacitance, a shift of the - , its narrowing, and the stiction by a closure of the pull-out window. We further show that the combined nonuniformities of air gaps and charges break the symmetry of the actuation characteristics. The asymmetry can be such that one of the pull-in points disappears, which is replaced by a continuous tuning range while the other pull-in point still exists.

A microwave microfluidic sensor for detecting binary liquid mixtures with a dielectric method at RF/microwave frequencies is presented in this article. The sensor is based on a split-ring resonator (SRR) that is implemented in a microstrip transmission line, with interdigitated electrodes (IDEs) being integrated into the ring for liquid detection. Based on the equivalent circuit of the IDE-SRR device and with a series of finite element simulations, the detection theory is developed, and the device design optimization is investigated. The validation measurements on water-isopropanol liquid mixtures with various concentrations show that the proposed IDE-SRR sensor has higher sensitivity than the previous standard SRR sensor. The IDE-SRR sensor is then used to detect two binary liquids, i.e., water-methanol mixtures and water-tetrahydrofuran mixtures. The measured effective permittivity results of the binary mixtures at RF/microwave frequency range are compared with the existing mixing models for binary dielectric mixtures at zero frequency.