A Microshield RF MEMS Shunt Switch

Dynamic Pull-in of Shunt Capacitive MEMS Switches

Micro-electro-mechanical-systems(MEMS) switches have low resistive loss, negligible power consumption, good isolation and high power handling capability compared with semiconductor switches. Lifetime of capacitive shunt switches strongly depends on the actuation voltage so low voltage switches is necessary to enhance its performance as well as to broaden its application area. This paper presents the design and simulation of low voltage capacitive shunt MEMS switches together with its RF performance for high frequency applications. The low voltage switches are realized by lowering the spring constant of the beam using serpentine spring designs together with large capacitive area so as to achieve the good RF performance as well. The pull-in voltage is analyzed with commercial CAD finite element analysis software CoventorWare. The electromagnetic performance in terms of scattering parameters, insertion loss, and isolation are analyzed with software Ansoft HFSS10. The switches achieved insertion loss $$<$$ < 0.47 dB in on state from 2 to 40 GHz; it provided better than 25 dB isolation in off state with a capacitance ratio of 94---96. The actuation voltage as low as 1.5 V with actuation area $$110\,\times \,100\,\upmu \mathrm{m^2}$$ 110 × 100 μ m 2 along with good RF performance is reported. The design parameter optimization including selection of appropriate number of meanders and its width found to be one of the most sensitive factors affecting the spring stiffness and actuation voltage.

Comparative Study of Perforated RF MEMS Switch

This paper presents experimental results for line-to-line coupling between adjacent coplanar waveguide (CPW) transmission lines. The CPW lines are fabricated on glass and low resistivity CMOS grade Si substrates coated with a 20/spl mu/m cyclotene polymer. From the measurement results it is found that the coupling increases with frequency on low resistivity silicon substrate while the coupling on glass shows relatively constant peaks. A spacing of 600/spl mu/m between CPW lines is required to avoid parasitic coupling less than 30dB for frequencies up to 30GHz when fabricated on low resistivity silicon, while a spacing of 200/spl mu/m is required when fabricated on glass. The conductor width (W) and the slot width (S) for low resistivity silicon is 80/spl mu/m and 45/spl mu/m, and on the glass substrate W = 150/spl mu/m, S = 30/spl mu/m. Based on full-wave EM simulation results, it is argued that the primary coupling mechanism is through the interaction of higher-order modes.

This paper presents the fabrication process of a thin suspended membrane on normal low resistivity silicon (LRSi), which is then utilized to design millimeter-wave (mm-wave) transmission line and passive circuits with low loss. First, two redistribution metal layers are formed on a plain LRSi wafer with benzocyclobutene in-between. Then, the wafer is thinned down and etched from backside with a specific pattern. Based on this process, a volume is introduced underneath the front side structure and the lossy LRSi substrate is replaced by air, which is the ideal substrate with no loss. Using this method, the substrate loss that contributes the majority part of total loss in mm-wave circuits on LRSi is eliminated. As the operating frequency goes into mm-wave region, the circuit size is scaled down so that the suspended portion is so small that it will not increase the mechanical instability of the structure. Therefore, the proposed suspended membrane on LRSi technology provides an excellent platform to construct mm-wave components. A U-shaped slotline resonator formed on the first redistribution layer is proposed and its quality factors are studied in detail. A second-order bandpass filter is designed and implemented by cascading two such U-shape slotline resonators. The measured frequency responses exhibit good filtering performance, with fractional bandwidth of 13.9% at 126.8 GHz, midband insertion loss of 3.9 dB and passband return loss larger than 14.2 dB. It demonstrates that the proposed suspended membrane on LRSi technology is an excellent candidate for designing low loss mm-wave components.

A micromachining process has been developed to create high impedance and low loss high aspect ratio coplanar waveguide (HARC) on low resistivity silicon. The process uses silicon DRIE to create an array of tall mesas that are spaced with a precise pitch. The silicon mesa array is then merged into a single solid SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> mesa using thermal oxidation. The solid SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> mesa creates a wide dielectric for use in high impedance HARC. The complete fabrication process includes DRIE, thermal oxidation, electroplating, planarization, and substrate removal to create HARC on low resistivity silicon with a planar surface. A high impedance HARC has been fabricated on silicon using this method. Measurements show that silicon substrate removal increases the line impedance from 20 Ω to 57 Ω, reduces effective dielectric constant from 6 to 2, and reduces attenuation constant from 33 dB/cm to 4 dB/cm @ 30 GHz. Measurements are compared to an analytical model derived for HARC.

Radio frequency micro electromechanical system (RF MEMS) based switches are widely used in microwave and millimeter wave communication systems for their low loss, excellent linearity, low power consumption and compact size compared to other contemporary solid state devices [1]. Surface micromachining technology is typically used to develop different types of single pole multi-throw (SPMT) switches like SPST, SPDT and SP4T. MEMS series and shunt switches are extensively used in SPMT RF switches for multiband selectors, filter banks, reconfigurable antennas and phase shifter applications in transmit/receive modules.

The paper presents a design and mathematical analysis of capacitive RF MEMS switch for achieving high isolation, low insertion loss and low pull in voltage. The proposed design includes central electrode for RF path and ground plane around it. Structure is simulated on silicon substrate with gold as the conducting material. Silicon dioxide is used as the dielectric layer to ensure better isolation of the switch along with reliability. High isolation of -35dB and insertion loss of less than -0.1dB is achieved for the frequency range upto 30 GHz. The structure has very low pull in voltage which gives it advantages in terms of low power consumption with other MEMS switches. RF design is implemented on CST microwave studio. Era of new wireless standards like 5G requires high linearity & wider bandwidth operation. RF MEMS switches have many wireless communication application including cellular base station, mobile handset and tunable filters etc.

Improvement of isolation for MEMS capacitive switch via membrane planarization

This paper presents a novel structure of capacitance shunt type RF switch for 5G applications. The proposed RF MEMS switch is having Cantilever type designed with optimized dimensions to operate in V-band applications. The electromechanical analysis is done by using the COMSOL tool. The actuation voltage of the proposed switch is 10.5 V with the air gap of 1 µm and gold as a beam material. The proposed switch with the meanders and perforations show the scattering parameters in HFSS software such as insertion loss (S12) of − 0.033 dB and return loss (S11) less than − 48 dB and the isolation (S21) calculated in off-state as − 62 dB at 50 GHz.

This paper presents a Tapered Tunable Transmission Line (Tapered TTL) phase shifter that achieves a higher area efficiency than conventional Tunable Transmission Line (TTL) phase shifters while maintaining the same phase shift range with similar insertion losses. A systematic methodology is provided for the optimum design of the proposed phase shifter to maximize its area efficiency while providing the desired phase shift range and satisfying the maximum allowed input/output return and insertion losses. To verify the efficacy of the proposed solution, an eleven-cell phase shifter is fabricated in a standard 65-nm Complementary Metal–Oxide–Semiconductor (CMOS) technology and the measurement results are reported. The fabricated circuit provides a 180-degree phase shift over the frequency range of 16.5 to 31 GHz with an average insertion loss of 7.2 dB. The proposed design presents a 25 percent reduction in the chip area per unit delay in comparison to the conventional design with the same average insertion loss.

In this work, a short wavelength microstrip line employing periodically arrayed capacitive elements (PACE) on GaAs monolithic microwave integrated circuit (MMIC) was developed for application to miniaturized on-chip passive components. The microstrip line employing PACE showed a wavelength much shorter than conventional transmission line. Concretely, the wavelength of the microstrip line employing PACE was only 10 % of conventional microstrip line on GaAs MMIC. Using the microstrip line employing PACE, a highly miniaturized impedance transformer was fabricated on GaAs MMIC. The impedance transformer showed good RF performances in a broad band from S to X band. Concretely, the return and insertion loss are −28 and −1.4 dB, respectively, at a center frequency of 7 GHz, and return loss values better than −10 dB were observed from 3.2 to 9.2 GHz, and insertion loss values of −1.5 ± 0.5 dB were observed in the above frequency range. The size of the impedance transformer was 0.042 mm2, which is 0.95 % of the size of the conventional transformer on MMIC.

This paper presents a unique model of shunt capacitive Microelectromechanical switch which works at RF frequency (12-18 GHz) with low insertion loss and high isolation. Low actuation voltage, removal of stiction and making a switch to work at Ku band frequency are main goals of this design. The ribs that are used in this model are made very stiff to avoid stiction problem. Hafnium Dioxide (HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) has been used as dielectric material with high dielectric constant (k~25) leading to high isolation. The designed switch is optimized to work at a very low actuation voltage (~11.32 Volt) with high isolation, -20 dB and low insertion loss, -0.095 dB.

In this paper, RF MEMS switch with capacitive contact is designed and analyzed for Ka band application. A fixed‐fixed beam/meander configuration has been used to design the switch for frequency band 10 GHz to 40 GHz. Electromagnetic and electromechanical analysis of three‐dimensional (3D) structure/design has been analyzed in multiple finite element method (FEM) based full‐wave simulator (Coventorware and high‐frequency structure simulator). A comparative study has also been carried out in this work. The high resistivity silicon substrate (tanδ = 0.010, ρ &gt; 8 kΩ − cm, εr = 11.8) with a thickness of 675 ± 25 μm has been taken for switch realization. The designed structure shows an actuation voltage of around 9.2 V. Impedance matching for the switch structure is well below 20 dB, loss in upstate, i.e., insertion loss &gt;0.5 dB, and isolation of &gt;25 dB throughout the frequency band is observed for the aforesaid structure. Furthermore, to increase the RF parameters, AIN dielectric material has been used instead of SiO2 resulting in capacitance in downstate that increases hence improved the isolation. The proposed switch can be utilized in various potential applications such as any switching/tunable networks phased‐array radar, reconfigurable antenna, RF phase shifter, mixer, biomedical, filter, and any transmitter/receiver (T/R) modules.

An analytical calculation of microwave actuation for shunt capacitive MEMS switches is presented. This calculation shows that the microwave signal deflects the beam according to the RMS voltage of the signal. In addition, heating of the beam due to dissipated microwave power is shown to play a significant role in microwave actuation.