RF MEMS Research Articles

RF MEMS In-Line Type Phase Detector With Large Dynamic Range

An in-line type X-band phase detector is presented in this letter. It is constructed by a power combiner and a capacitive power sensor with clamped-clamped beam to obtain large dynamic range with respect to RF power. The fabrication process is based on MEMS technology. The experiments show that the return loss is smaller than −12.3 dB over X-band, the isolation is better than −9.1 dB and the insertion loss is around −3.5 dB. The conversion between phase, power, and capacitance is accomplished inside the detector for phase detection from 0 to 180°. The varying capacitance of the beam can sustain a dynamic range of 0.25 ~ 2 W with satisfactory detection sensitivity, 163.8aF/deg. at 2W. Third-order intermodulation distortion (IM3) of the detector is rather small and the IIP3 is about 37.4 dBm for 10-kHz frequency interval.

Beam and dielectric materials impact on improvement of the performance of a novel capacitive shunt RF MEMS switch

AbstractThis paper presents a novel radiofrequency micro‐electro‐mechanical systems (RF MEMS) shunt capacitive switch having high isolation and low insertion loss for microphone applications. The device optimization and various electromechanical analysis are performed using a finite element modeler (FEM) solver. The proposed switch results in a pull‐in voltage of 36.88 V to displace movable beam 2/3rd of its initial gap. By varying beam material, dielectric material, beam‐dielectric thickness, and air gap between movable beam and dielectric layer, various electromechanical and electromagnetic analyses are carried out. For better isolation, silicon nitride (Si3N4) is used for the dielectric layer than hafnium oxide (HfO2) and silicon carbide (SiC). To achieve maximum displacement of the beam, various materials such as aluminum, gold, nickel, and copper are chosen; among all, this gold shows high displacement because of its good conductivity. By implementing various meandering techniques along with perforations, pull‐in voltage and stiction problems are reduced. The switch exhibits good return loss of −28 dB and insertion loss of −0.017 dB during on‐state at 5 GHz and high isolation of −41.26 dB at 10.5 GHz during off‐state. The proposed switch is used at the subsystem/device level in the future microphone, aircraft navigation, and satellite applications.

Design and optimization of a novel high isolation low insertion loss RF MEMS single-pole double-throw switch

This paper designs an RF MEMS single-pole single-throw and single-pole double-throw switch based on the Ka-band on the CPW. The electrodes of the switch are sandwiched by two dielectric layers. Each SPDT switch has a resonant frequency of approximately 35 GHz and a bandwidth of 20 GHz with an isolation greater than -38 dB and an insertion loss less than -0.8 dB. By changing the state of the SPDT switch, one is in the up state and the other is in the down state, it can achieve the function of switching on and off. The SPDT switch also operates at around 35 GHz with a return loss greater than -23 dB, an insertion loss of less than -1 dB, and an isolation greater than -38 dB.

An MRI Compatible RF MEMs Controlled Wireless Power Transfer System.

In magnetic resonance imaging (MRI), wearable wireless receive coil arrays are a key technology goal. An MRI compatible wireless power transfer (WPT) system will be needed to realize this technology. An MRI WPT system must withstand the extreme electromagnetic environment of the scanner and cannot degrade MRI image quality. Here, a WPT system is developed for operation in MRI scanners using new microelectromechanical RF switch (RF MEMs) technology. The WPT system includes a class-E power amplifier, RF MEMs automated impedance matching, a primary coil array employing RF MEMs power steering, and a flexible secondary coil with class E rectification. To adapt WPT technology to MRI, techniques are developed for operation at high magnetic field, and to mitigate the RF interactions between the scanner and WPT system. A major challenge was the identification and suppression of noise and harmonic interference, by gating, filtering, and rectifier topologies. The system can achieve 63% efficiency while exceeding 13 W delivery over a coil distance of 3.5 cm. For continuous WPT beyond 5W, added filters and full-wave class E rectification lowers harmonic generation at some cost to efficiency, while image SNR reaches about 32% of the ideal. RF-gated WPT, which interrupts power transfer in the MRI signal acquisition interval, achieves SNR performance to within 1 dB of the ideal. With further refinement, the inclusion of WPT technology in MRI scanners appears completely feasible.

Design and performance analysis of self-similar reconfigurable antenna by cantilever type RF MEMS switch

RF MEMS switch is an excellent choice for the implementation of reconfigurability in antenna due to its good electromagnetic characteristics. In this paper, the cantilever type RF MEMS switches are used as a connecting element between the antenna patches. The shift in the frequency of the antenna is observed by integrating and actuating the different combination of cantilever switches. The proposed switches are same type of cantilever switches with same pull-in voltage of 5.5 V have been used in the antenna. Here, the lateral left shift of 1.5 GHz is observed from the condition 1 to conditions (2 and 3) and 4.3 GHz of frequency shift in condition 4 is observed from the antenna. The overall bandwidth of 4 GHz is observed in the antenna with the integration of RF MEMS switches in different combinations.

Laterally Movable Triple Electrodes Actuator toward Low Voltage and Fast Response RF-MEMS Switches.

A novel actuator toward a low voltage actuation and fast response in RF-MEMS (radio frequency micro-electro-mechanical systems) switches is reported in this paper. The switch is comprised of laterally movable triple electrodes, which are bistable by electrostatic forces applied for not only the on-state, but also the off-state. The bistable triple electrodes enable the implementation of capacitive series and shunt type switches on a single switch, which leads to high isolation in spite of the small gap between the electrodes on the series switch. These features of the actuator are effective for a low voltage and fast response actuation in both the on- and off-state. The structure was designed in RF from a mechanical point of view. The laterally movable electrodes were achieved using a simple, low-cost two-mask process with 2.0 µm thick sputtered aluminum. The characteristics of switching response time and actuation voltage were 5.0 µs and 9.0 V, respectively.

A study of the effect of transient stresses on the fatigue life of RF MEMS switches

AbstractFatigue affects the durability of radio frequency microelectromechanical systems (RF MEMS) devices. It is common to rely on actuation voltage cycles or resonant frequencies shift to estimate the fatigue life of MEMS devices. Actuation of moving mechanical parts within the device causes transient stresses because of transient vibration. Such stresses and stress cycles are difficult to account for when fatigue life is estimated by observing actuation voltage or resonant frequencies shift only. This work investigates the effect of transient stresses on the durability of RF MEMS switch, using a benchmarked finite element‐based structural dynamics model of the switch to generate the stress‐time history of the device. Principal normal stresses are calculated from raw stress data and ordered such that (σ1 ≥ σ2 ≥ σ3). Maximum principal stress amplitudes at pull‐in and pull‐out are calculated, and their corresponding number of cycles are determined by rainflow counting method. A Cumulative damage index (Dc) is determined using Miner's rule. This study revealed that, when transient stresses are taken into consideration, the cumulative damage caused by a single on‐off cycle, of the switch studied, is 1.031 × 10−6, and its life‐to‐failure is 9.7 × 105 on‐off cycles. Whereas the life‐to‐failure of the switch, without considering transient stresses, is approximately 10.3 × 108 cycles. Results are compared with published data for similar switches, and they are in good agreement.

Compact high isolation and improved bandwidth hybrid RF MEMS SPDT switch for 5G applications

Fifth generation (5G) communication system enables the pathway for a higher data transfer rate. The frequency bands used for 5G communication system are distributed from lower frequency range (600 MHz) to a higher frequency range (60 GHz). So it is necessary that a single switch should be able to cover the complete range of 5G frequency bands. The ohmic radio frequency-micro electromechanical system (RF-MEMS) switch has offered high isolation at lower frequencies (> 40 dB up to 2.5 GHz). However, 5G requires a higher frequency range which is covered by capacitive switch. The capacitive switch has limitations of limited bandwidth and large size. In this paper, a hybrid technique is used for the designing of a compact, high isolation and the enhanced bandwidth SPDT RF MEMS switch for 5G applications. The size of the proposed switch is half from the conventional capacitive RF MEMS switch and offer greater than 40 dB isolation over a wide frequency range (> 40 dB over 22.10 GHz bandwidth) with less than 0.30 dB insertion loss over the entire band.

Analysis of Thermally Actuated RF-MEMS Switches for Power Limiter Applications

This paper presents a multiphysics analysis of thermally actuated RF MEMS switches for use in power limiter applications. RF MEMS switches can self-actuate when operating under high RF power levels. The level of power at which the switch actuates, can be varied by controlling the applied dc actuation voltage. MEMS switches are, therefore, proposed for use in power limiter applications. The objective of the multiphysics analysis presented in this paper is to combine thermal analysis, with mechanical analysis and RF analysis to derive a relationship between the RF power needed for self-actuation and the dc voltage applied to the thermal actuator. A thermally actuated MEMS switch is fabricated and tested. It is used as a test bed for demonstrating the proposed multiphysics analysis. The experimental results obtained for this switch confirm the approach used to construct a multiphysics analysis for thermally actuated MEMS switches. The results obtained also demonstrate that thermally actuated MEMS switches offer improved device sensitivity, when used in power limiter applications, in comparison with their counterparts electrostatically actuated MEMS switches. [2018-0106]

SR‐Crossbar topology for large‐scale RF MEMS switch matrices

With the development of multifunctional satellites, the integration and multiplexing of satellite resources become increasingly important. Large-scale radio-frequency microelectromechanical system (RF MEMS) switch matrix technology is one of the key technologies to design a multifunctional satellite. This study proposed a novel sequential rotation crossbar (SRCrossbar) topology for large-scale RF MEMS switch matrices. A specifically designed novel configuration scheme or arraying method for SR-Crossbar topology is also proposed. The number of switch elements in the SR-Crossbar RF MEMS switch matrix is significantly reduced; hence, the reliability and performance of the matrix can be improved simultaneously. For an N × N RF MEMS switch matrix, in a fully configured scenario, the maximum number of switch elements in all the paths are N(N + 1)/2. When N ≥ 4, the proposed SR-Crossbar RF MEMS switch matrix topology is better than the planar Benes topology, which is already an optimised planar switch matrix topology with the minimum number of nodes.

Effect of Parasitic Capacitance on RF MEMS Switch OFF/ON Ratio

Radio frequency micro-electro-mechanical system (RF MEMS) switch is basic component for transponders used in communication system. Switch “OFF/ON” capacitance ratio plays major role in controlling signal to noise ratio. Theoretically, with high dielectric constant material or floating metal concept, capacitance ratio can be improved up to 2000 or even more. Whereas, in most of the practical cases, measured ratio is less than 200. In present paper, RF MEMS capacitive switch LCR parameters are extracted considering parasitic capacitance to explain the mismatch of measured results. Parasitic capacitance is independent from device overlap area. Parasitic capacitance is function of switch geometry and directly proportional to dielectric constant of the substrate material.

Determination of the stiffness properties of a complex RF MEMS by superposition and finite elements method

In this study, the deflection and stiffness of a micro cantilever beam with a rectangular notch are derived analytically by considering a non-uniformly distributed load as a cause of deflection, since the shape of a distributed load at the exact collapse time is not uniform in the real scenario. In order to calculate the deflection, due to the design of the beam structure, the superposition method is employed as well as the fundamental principles of mechanics. Moreover, it is also utilized in the subsequent stiffness calculations. Particularly, the stiffness concept is discussed under three different subsets: natural, actuation, and release stiffness, as they are essentials for the switching operations. In addition to the analytical study, FEM simulations are also carried out using CoventorWare in order to compare with the derived models. As the results reveal that accuracies of both the analytical models and simulations are acceptable, this study provides a utilitarian framework for designing different complex MEMS.

Design and Performance Analysis of Low Pull-In Voltage of Dimple Type Capacitive RF MEMS Shunt Switch for Ka-Band

This paper deals with the study of dimple type RF MEMS capacitive shunt switch using different meandering techniques for high isolation and low actuation voltage. The novelty of the proposed RF MEMS switch is it incorporates the meanders and dimples, which help to reduce the actuation voltage. The proposed switch structure is optimized, designed, and simulated with FEM analysis such as electromechanical and electromagnetic by using COMSOL and HFSS tools respectively. The best performance of the switch is observed by varying different parameters such as beam material, beam thickness, dielectric thickness, and airgap. The proposed switch with different meandering techniques attains the pull-in voltage in the range of 10.3-46 V, particularly the three uniform meander technique has low actuation voltage of 10.3 V. The RF performance of the device is particularly tuned in the range of 26.5-40 GHz frequency range and it is analyzed for all types of meanders. Among them, the non-uniform single meander has attained the best isolation of -54.13 dB at 40 GHz in the off state. The insertion and return losses of the device are -0.514 dB and -17.35 dB over 1-40 GHz frequency in on state.

Comprehensive Study on RF-MEMS Switches Used for 5G Scenario

This paper presents a comprehensive study on radio frequency-microelectromechanical systems (RF-MEMS) switches, which are expected to be extensively integrated into 5G infrastructures. The specifications of the RF-MEMS switch in use case and scenario for 5G have been summarized in part 2 and followed by the study of the state-of-the-art RF-MEMS switches in part 3. Both metal-contact and capacitive RF-MEMS switches, which have been developed and fabricated within the last two decades, are studied and tabled. In order to meet with the specification requirements of 5G scenario, the performance and characteristics of the RF-MEMS switches should be enhanced, such as acceptable RF performance, low actuation voltage, good reliability, short switching time, multiband topology, and on-chip integration and packaging. Different techniques for the improvement of the RF-MEMS switches' properties, for instance low spring constant, large actuation area, diverse actuation methods, push-pull mechanism, modified driving voltage waveform, inductive compensation, and so on, have been thoroughly investigated, classified, and summarized in part 4, which serves as the main contribution of the review. The findings from this review can be beneficial for further RF-MEMS switches' design and improvement. The upgraded RF-MEMS switches are capable of satisfying the growing need of cutting edge performance for 5G or high-performance applications.

Design, Modeling and Analysis of Perforated RF MEMS Capacitive Shunt Switch

This paper illustrates the design, modeling, and analysis of bridge type structure based capacitive RF MEMS switch with different beam thickness and materials. We have used Ashby’s approach to select the best materials in each and every level which helped to improve the overall performance of the switch in terms of mechanical, electrical, and RF properties. Silicon Nitride thin film ( $\varepsilon _{\mathrm {r}}= 7.8$ ) is used as a dielectric material. The beam structure stiffness is analyzed with different materials, such as gold, titanium, and platinum, within these materials gold with high thermal conductivity and Euler–Young’s modulus of 77 GPa is offering the best performance. Incorporation of meanders and perforations to the membrane helped to reduce the pull-in voltage. The proposed switch is offering very low pull-in voltage of 1.9 V. The deflection of beam thickness is tabulated for the three materials among them the 2 $\mu \text{m}$ thickness is best beam thickness for the switch for X-band applications. The switch offers best return loss (S11) of −21.36 dB, insertion loss (S12) of −0.147 dB, and isolation (S21) of −52.04 dB at 8GHz. The switch presented in this paper is preferable in X-band applications.

Об одной методике проектирования топологии ВЧ МЭМС-ключа

Об одной методике проектирования топологии ВЧ МЭМС-ключа

Reduced dielectric charging RF MEMS capacitive switch

The presence of dielectric charging in a switch causes stiction and drift in pull-in voltage. A design to alleviate charging issues for RF MEMS switches is proposed. An RF MEMS capacitive switch has been fabricated and characterized. Measured pull-in of the switch is <20 V and pull-up voltage is 17 V with a switching time of 78 μs. Insertion loss and isolation of the switch are measured by varying RF power from 0 to 15 dBm at room temperature. Insertion loss and isolation of the switch are better than 0.1 and 17 dB, respectively. Resonant frequency of the device is 8.4 kHz. The switch has completed 600 million cycles.

Analytical Approach in the Development of RF MEMS Switches

Currently, the technology of microelectromechanical systems is widely used in the development of high-frequency and ultrahigh-frequency devices. The most important requirements for modern and advanced devices of the ultra-high-frequency range are the reduction of weight and size characteristics, power consumption with an increase in their functionality, operating frequency and level of integration. Radio frequency microelectromechanical switches are developed using the technology of the manufacture of CMOS-integrated circuits. Integrated radio frequency control circuits require low control voltages, the high ratio of losses to the isolation in the open and closed condition, high performance and reliability. This review is devoted to the analytical approach based on the knowledge of materials, basic performance indices and mechanisms of failure, which can be used in the development of radio-frequency microelectromechanical switches.

Design and analysis of perforated MEMS resonator

In this paper, we have designed an optimal design of microelectromechanical (MEMS) resonator. The paper explains the idea of suitable design, modeling and optimization of the MEMS RF resonator. The resonator has been designed to achieve a high quality factor and optimum pull in voltage and keeping the dimension as small as possible. The design approach uses the Dragonfly algorithm for minimizing the pull in voltage. The resonator is basically a perforated structure incorporating circular holes.

Design and Analysis of Serpentine Flexure Based RF MEMS Switch for High Isolation with Low Pull-in voltage

This paper presents the design and performance analysis of radio frequency micro electro mechanical system switches having serpentine flexure designs. In this paper, we have done, behavioral analysis by changing material, gap and thickness, increase in the actuation area using menders, impact of holes on effective working of the switch, stress analysis for low spring constant, electromechanical analysis for low pull-in voltage and high capacitance ratio, time dependent analysis for faster switching time, scattering parameter analysis for reducing RF losses are simulated and compared with the theoretical analysis. The significant improvements in this work are lesser air gap and beam thickness reduced the pull-in voltage to 2.75 V for 1.66 µm displacement, a rapid switching time of 0.9 µs obtained through simulation, an improved capacitance ratio of 157.25, isolation is 49.59 dB, insertion loss is 0.005 dB. Actuation area is increased, and switch area is reduced to achieve the optimum performance of the switch.