Variable pivot seesaw actuated RF MEMS switch for reconfigurable system application

This paper presents the design, analysis, modeling and simulation of a novel RF MEMS series switches with low actuation voltage. A mechanical modeling is presented to describe the behavior of the series switch. The switch is designed with special mechanical structures. The novel mechanical and mathematical modeling of the switch leads to calculation of the accurate actuation voltage. The spring constant has been calculated in relation to the presence of the residual stress in the beam. The calculated spring constant for this beam is used to determine the accurate actuation voltage. The size of the switch is 60 ? 110 µm2. The designed RF MEMS series switch was simulated using Intellisuite MEMS tool. He calculated actuation voltage is 4.05 V and simulated one is 4.2 V for 0.6 µm beam thickness. The calculated result is also very close with simulated one. The proposed switch compared with other electrostatic switches has low actuation voltage and small size. The RF characteristics were simulated using HFSS software and the switch has good RF performance. The insertion loss of 0.067 dB, return loss of 26 dB and isolation of 16 dB were achieved at 40 GHz.

RF-MEMS switches may be divided into capacitive and metal-to-metal types in terms of type of connection. In capacitive switches in the OFF-state the beam does not attach to the transmission line due to the presence of a thin dielectric layer and it gets released easily. Capacitive switches are better compared with the metal-to-metal types due to their ability to transmit signals of higher frequency and power. In this paper, a novel RF MEMS shunt capacitive switch with a unique spring design is proposed. The proposed design benefits from high isolation, low loss, low actuation voltage, small size and weight compared to similar switches and is designed for application in the Ka-band. Step structure is used in the mechanical design of the switch to reduce the air gap between the bridge and the transmission line that has resulted in reduction of actuation voltage to 2.2 V. The proposed switch has been placed upon a coplanar waveguide (CPW) line with an impedance of 50 Ohms. $${\text{SiO}}_{2}$$ with a thickness of 1000 A has been used as dielectric to increase isolation and down-state capacitance. The unique design of the spring results in the reduction of stress to a minimum at all points of the switch especially the springs at the time of applying the actuation voltage. This advantage would reduce switch failures as time passes and results in increased life of the switch. Up-state capacitance is 93.3 fF and down-state capacitance is 2.64 pF. Therefore, a capacitive ratio of 28 is obtained. The dynamic behavior of the switch is studied by using the COMSOL Multiphysics software package and the RF characteristics have been obtained by using the HFSS software and show good RF performance. The results show that in the up-state, the designed switch including S11 is less than − 11.5 dB and S21 is more than − 0.85 dB at 1–40 GHz. In the down-state, the switch has excellent isolation in the Ka-band. Maximum isolation is − 71 dB that occurs at the resonance frequency of 30.5 GHz.

A vertical RF-MEMS (Radio Frequency Micro ElectroMechanical Switch) switch design is proposed in this work that features a shunt capacitive configuration and can operate at a very low actuation voltage. Besides operating on a low switching voltage, the switch behold a small value of insertion loss in Up (ON) state and offers a towering isolation factor in Down (OFF) state. A horizontal structure of bridge membrane is used in the proposed design and the switch function (with ON and OFF operating states) is provided by the vertical movement of this membrane structure that is controlled by the electrostatic actuation technique. The actuation pad is centrally fed by a Coplanar Waveguide structure. The switch performance has been analysed over a wide frequency range from 1 to 40 GHz. For obtaining a 1.5 μm vertical displacement of the bridge membrane, a sheer 3.0 Volts of pull-in voltage (VPI) is required. CoventorWare and HFSSv13 tools are used in this work for designing and analysing the proposed switch. The use of fixed-fixed flexure beam configuration is chosen for switch design. Simulation results showcase excellent RF characteristics with isolation factor of −47 dB (at 32.5 GHz) and insertion loss in range of −0.01 to −1.10 dB (for 1−40 GHz frequency).

This paper reports the design, fabrication, electrical characterization and packaging of micromachined shunt capacitive switch with low actuation voltage. These switches are fabricated on a low resistive silicon substrate using only a four mask surface micromachining process. The co-planar waveguide is patterned using chrome/gold layer. Positive photoresist S1813 is used as the sacrificial layer. The top beam membrane is made of gold. The membranes are released through a wet release process through Piranha solution. Supercritical point drying tools were used for the top beam release after wet etching to provide anti-stiction. The switches are 300 µm long with 10 μm holes on the top membrane to lower both residual stress and pull-in voltages. These switches exhibit low actuation voltages in the range of 5.5–6.4 V. The RF characterization shows that these switches have low insertion loss and high isolation in the frequency range of interest. The packaging was carried out using commercially available surface mount style RF packages. However, the whole packaging process is performed under low temperature in order to free the MEMS structures of thermally induced stress which otherwise would affect the performance of the switch. The adhesion of the die to the bottom package is excellent and is tested by die shear test. The packaged switch has passed the non-destructive pull test.

This paper presents the design and RF characterization of micro electromechanical system (MEMS) switches realized on Elevated Coplanar waveguide for high-speed applications. The capacitive air gap between signal line and the cantilever is 1um. The lowest actuation voltage obtained is 6V. The insertion loss of switch and its associated transmission line is −0.31dB (mainly contributed by the transmission line itself) and the isolation was around −21.67dB at 40GHz.

In this work, the coplanar waveguide is fabricated on a PES (poly[ether sulfone]) substrate for application to a flexible monolithic microwave integrated circuit, and its RF characteristics were thoroughly investigated. The quality factor of the coplanar waveguide on PES is 40.3 at a resonance frequency of 46.7 GHz. A fishbone-type transmission line (FTTL) structure is also fabricated on the PES substrate, and its RF characteristics are investigated. The wavelength of the FTTL on PES is 5.11 mm at 20 GHz, which is 55% of the conventional coplanar waveguide on PES. Using the FTTL, an impedance transformer is fabricated on PES. The size of the impedance transformer is 0.318 mm × 0.318 mm, which is 69.2% of the size of the transformer fabricated by the conventional coplanar waveguide on PES. The impedance transformer showed return loss values better than –12.9 dB from 5 GHz to 50 GHz and an insertion loss better than –1.13 dB in the same frequency range.

Innovative micromachined microwave switch with very low insertion loss

In this paper, a novel MEMS microwave power sensor employing the coplanar waveguide (CPW), which is consist of the linearly graded signal line and ground planar, is presented to avoid step discontinuity. Then the design of the proposed power sensor is described in detail. Through compared to the simulation results of the device with the abrupt signal line and ground planar, the proposed device can obtain better microwave performances. The fabrication process is compatible with GaAs MMIC technology completely and also described in this paper. The capacitance change, return and insertion losses have been measured. The measurement results indicate that the proposed power sensor is characterized by a sensitivity of 20 aF mW−1 for 400×200 µm2 fixed-fixed beam and superior return and insertion losses (S 11 and S 21 ), which are less than −25 dB and −0.35 dB, respectively, up to 14 GHz.

This paper presents an approach for restoring force enhancement to radio frequency (RF) micro-electro-mechanical systems (MEMS) switch with stiction-recovery actuation mechanism. It is based on additional anti-stiction electrodes which are inserted to the coplanar waveguide (CPW) between the signal line and ground planes of a RF MEMS switch. If the movable membrane sticks to the substrate, electrostatic force, as extra restoring force, generated by the bias voltage between the anti-stiction electrodes can promise restoring action. The designed device with the proposed approach is fabricated. The restoring force of the fabricated device had reached 75, 177 and 520 μN by the bias voltages of 0, 10 and 20 V, respectively.

In this paper, we propose the design of an ohmic contact RF microswitch with low voltage actuation, where the upper and lower microplates are displaceable. We develop a mathematical model for the RF microswitch made up of two electrostatically-actuated microplates; each microplate is attached to the end of a microcantilever. We assume that the microbeam is flexible, the microplates are rigid bodies and the electrostatic force is nonlinear function of the displacement and voltage applied between the microplates. We formulate the static and eigenvalue problems associated with the proposed microsystem. We show that the resulting static pull-in voltage and switching time are reduced by 30 and 45%, respectively, as compared to those associated with a RF microswitch formed of a single microbeam-microplate system. We also show that, unlike the second and higher frequencies, a selected range of applied DC voltages, affects significantly the first frequency.

This paper presents the design, fabrication and testing of capacitive copper RF MEMS switches with various hinge geometries, fabricated on high-resistivity silicon substrates. The switches were fabricated using a simple low-cost four-mask process and 0.6-1.0 /spl mu/m thick membranes were made out of sputtered copper. The capacitive airgap in between the membrane and the signal line is 1.5-2.0 /spl mu/m. The lowest actuation voltage measured on the fabricated switches is 9 V. The measured insertion loss of a fabricated switch and its associated transmission time was 0.9 dB (mainly contributed by the transmission line itself) and the isolation was measured to be 25 dB at 40 GHz.

We investigated the propagation losses and the characteristic impedances Z/sub L/ of coplanar waveguides (CPWs) and microstrip lines (MSLs) on a planar lightwave circuit (PLC)-platform formed on a silica/silicon substrate. The loss of the CPWs was 2.7 dB/cm at 10 GHz on the PLC-platform with 30 /spl mu/m thick silica layer. Thus, a cm-order circuit of this CPW is difficult to fabricate in the 10 Gb/s module. This is because the silicon substrate has a large loss tangent (tan /spl delta/). On the other hand, the loss of the MSLs, where a ground plane shielded the high loss silicon substrate, could be improved to 0.9 dB/cm at 10 GHz with 30 /spl mu/m thick polyimide. These lower loss MSLs on a PLC-platform can be applied to module operation at 10 Gb/s. Furthermore they have the advantage that they are suitable for application to array device circuits or circuits in a module where several devices are integrated because unlike CPWs the ground planes are not divided by signal lines or DC bias lines. The structure of CPWs and MSLs on a PLC-platform with a Z/sub L/ of 50 /spl Omega/ was also studied in detail.

Microwave switches are extensively used in many wireless and satellite communication systems. They are mainly used for signal routings and reconfigurations. Recently, due to the development of micro-mechanical systems (MEMS), RF MEMS switches are being widely investigated. Although RF MEMS switches have been intensively studied, limited work was done on switches that are suitable for integration in large switching networks such as switch matrices and multi-bit phase shifters [1, 2]. These switching networks require very small switches each with independent controls. Their major existing problems are the high actuation voltage and the low switch yield. High actuation voltage is undesired as a more complicated circuitry is required to provide suitable control signal. Low yield is another drawback as it could result in malfunctioning of some of the switches and thus the entire integrated system. One of the major contributions in resulting of low yield in RF MEMS switches are their dependency to the residual stress of the fabrication process both across one wafer and across batches. This problem is much more pronounced on switches with long length as they deform to their curled shape and prevent switching. In this paper, a novel type of switch is proposed that could reduce the stress sensitivity of the switch as well as providing a low actuation voltage. The overall switch structure is design with size miniaturization.

We report the first ever silicon carbide (SiC) nano-electro-mechanical systems (NEMS) switches capable of operation from 25 to 600degC. We have developed both laterally- and vertically-actuated designs with threshold voltages of less than 5 V. Switches have been verified to cycle more than 3 billion times at room temperature and more than 2 million times at 600degC. Plausible models to describe the contact resistance in two actuation voltage regimes are also suggested: (i) at low actuation voltage, the resistance is dominated by the native oxide which forms on the SiC surface; and (ii) at higher actuation voltages, the resistance can be described by Sharvin's model.

Low Actuation Wideband RF MEMS Shunt Capacitive Switch