Figure 14 shows the RF measurement setup of the switch.īlock diagram of RF MEMS switch lifespan test platform. The sweep frequency ranged between 10 MHz and 40 GHz. To contact the two ends of the switch, two gold ACP-A-GSG-150 probes (Cascade Microtech, Beaverton, OR, USA) were utilized, and the device was put on a probe table (Cascade Summit 11000B-M, Cascade Microtech, Beaverton, OR, USA). The S (S 11 and S 21) characteristics of the RF MEMS switch were measured using a vector Network Analyzer (R&S ZVA50, Rohde & Schwarz, Munich, Germany). An Agilent E3631A provided the DC voltages. The temperature and relative humidity of the measurement environment were 24 ☌ and 40%, respectively. The measurements were conducted in an ultraclean room. The S 21 value between the input and output can be used to determine isolation and insertion loss. When the RF MEMS switch is in the up-state (namely ON state), the insertion loss displays the signal loss, and when the RF MEMS switch is in the down-state, the isolation shows the signal isolation level (namely OFF state). On the contrary, the MAM capacitor is transformed to a resistance R when the MEMS switch is in the down-state. When the MEMS switch is in the up-state, a MIM capacitor is connected in series to a MAM capacitor. The upper metal plate of the MIM capacitor, the beam and the air combine to form a MAM capacitor. In this article, a MIM capacitor is situated below the beam. A MIM capacitor, which acts as a shunt capacitor on one side of the CPW ground plane, was proposed in. Connecting a MIM capacitor to the shunt capacitor C metal–air–metal (MAM) is a simple and practical way to get a high capacitance ratio in a MEMS switch, as shown in Figure 5. Therefore, it is difficult to achieve low pull-in voltage and a larger capacitance ratio for traditional MEMS switches simultaneously.Īs illustrated in Figure 4, when g = 1.5 μm, Cr is less than 80 for typical MEMS switches using the circuit model of Figure 3. However, due to the pinhole problems in the dielectric layer, we can not deposit a Si 3N 4 layer less than 0.1 μm, and the dielectric layer should be able to sustain the excitation voltage without being pierced. Therefore, a low insertion loss, high isolation and larger capacitance ratio RF MEMS switch has been designed and fabricated.įrom Equation (3) and Figure 4, we may deduce that the capacitive ratio C r rises as g (the gap between the beam and the electrodes) rises and falls as t d (the thickness of the dielectric layer) rises. As a result, the ways used in are not the most suitable.īased on the floating metal membrane, this research increases the capacitance ratio of the RF MEMS switch. However, the capacitance ratio is constrained by the minimum dielectric layer thickness, the maximum dielectric constant value and the maximum distance between the beam and the signal transmission line. The other approach of achieving a high capacitance ratio is to widen the distance between the MEMS beam and the dielectric layer. use materials with a high dielectric constant to get a larger capacitance ratio. There has been some research done in larger capacitance off/on ratios to date. For example, the capacitance ratio of the switch controls the adjustable range of the center frequency of the resonant unit in the tunable filter. A larger off/on capacitance ratio is advantageous for achieving high isolation and outstanding RF performance. The actuation voltage represents the switch’s integration performance, which contributes to the development of a monolithic microwave-integrated circuit (MMIC). Secondly, the capacitance ratio is not very high. First, the driving voltage of the MEMS switch increases as the beam height increases. However, there are a few issues to be resolved. Rodriguez tells us that RF MEMS switches and transmission lines can realize the function of phase shift so that they can point out the antenna beam to a desired location with high precision. describe the potential applications of RF MEMS switch matrices in the satellite industry, wherein mass reduction and performance improvement are crucial. RF MEMS switches are widely used in radar, satellite communication systems, smart antennas with beam forming and phased array capabilities, tunable filters, phase-shifting networks and other important fields. address the fundamentals of RF switches, providing a comparison between semiconductor and RF MEMS switches. Compared with PIN diodes and FETs, RF MEMS switches are smaller in size, lighter in weight, less sensitive to acceleration, no DC power at microwave frequencies and have excellent isolation and insertion loss.
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