A Tunable Capacitor Based on MEMS Technology for RF Applications

Abstract

A tunable capacitor based on MEMS technology is presented in this paper. The proposed structure consists of two fixed-fixed parallel movable plates with 4 supports. Movability of two plates makes it possible to actuate the plates with a small voltage. When the actuation is applied, two plates move together and their distance is decreased, hence the capacitance is increased and tuning is achieved. The structure is simulated through the finite element method using COMSOL and ANSOFT HFSS software. Simulation results show that the actuation voltage required to access the 59% tuning, is 7 V. The effective area of the designed tunable capacitor is 200 x 200 µm2 with a thickness of 2 µm. The quality factor is 91 at 11 GHz which is sufficient for various RF communication applications such as filters, transceivers and so on. The low stress induced on the plates and low actuation voltage, are the main advantages of the design.

Compact Circularly Polarized Patch Antenna for WiMAX Applications with Improved Impedance Bandwidth and Axial Ratio

“…Circularly polarized antennas are more useful in wireless communications, RFID (radio-frequency identification), wireless LAN, and GPS. As of today these are the most opted due to the flexibility in the antenna positioning, the fewer misalignment losses, and the less interference between signals [4][5]. Circular polarization is classified by the number of feed points on the microstrip antenna.…”

On the implementation of adaptive sliding mode robust controller in the stabilization of electrically actuated micro-tunable capacitor

“…Micro-tunable capacitors are miniature micro-sized structures that find various applications ranging from wireless systems to even high frequency-based circuits. They have attracted the attention of several researchers resulting into the publication of a significant research work [1][2][3][4][5] mainly devoted into considering these tiny structures in the design of numerous devices such as voltage control micro-oscillators [6,7], micro-filters [8][9][10], super-heterodyne micro-transceivers [11], etc… Tunability represents one of most important characteristics for micro-tunable capacitors, which is mainly be governed by the difference between their respective maximum and minimum capacitance values. The more the maximum capacitance is accomplished, the higher the tunability is.…”

“…The more the maximum capacitance is accomplished, the higher the tunability is. Microelectromechanical (MEM) parallel-plates based micro-capacitors have been widely used in communication transceivers [5] owning high tunability because of numerous reasons: the ease of implementation as simple tuning mechanisms, their low area consumption, their high quality factor and straightforwardness in their fabrication. Indeed, there are three major techniques to possibly increase the tunability of parallel-plates micro-capacitors:  Regulation of the electrodes initial gap distance [12][13][14],  Optimization of the effective actuated parallel-plates area [15,16], and  the dielectric displacement method [5,17].…”