RF MEMS Research Articles

Design of Step down Structure RF-MEMS Shunt Capacitive Switch for Low-Pull-In Voltage

In this paper, designs and simulations of a new RF MEMS step-down structure of a capacitive shunt switch using different meandering methods are presented. The beam and dielectric materials are taken as gold and silicon nitride for the proposed switch. The switch required actuation voltage is 7.9 V for the non-uniform one meander technique.

Design, and Analysis of Capacitive Shunt RF MEMS Switch for Reconfigurable Antenna

This paper presents design and the performance analysis of capacitive shunt RF MEMS Switch. Here, the proposed Rf MEMS Switch shows the low pull-in voltage i.e 11.97 V and performed at 38 GHz with high isolation. To improve the performance of antenna characteristics microstrip feeding technique and co-planar-waveguide transmission line feeding are used in this design process. The impedance matching of 50Ω in the antenna is depends on the width of the feed line can be observed through simulated smith chart by using the Ansoft HFSS simulator. The micro strip patch antenna exhibits a Return loss is − 12.4264 dB and exhibits resonance at 38 GHz and the band width frequency from 37 to 39 GHz.After analyzing the performance of the antenna then the antenna is integrated with RF MEMS capacitive shunt switch through co-planar wave guide transmission feedline technique. By integrating with switch there is a frequency shift OF 1 GHz toward right from 38 GHz in antenna. The resonance is occurred at 39 GHz with bandwidth frequency between 38 and 40 GHz. The antenna exhibits return loss is − 27.2666 dB at operating frequency 39 GHz with RF MEMS switch and total gain of the antenna at 38 GHz with angle of ϕ = 90° is 5.6671 dB. Thus the performance of the antenna is increased by integrating with RF MEMS switch. These type of reconfigurable antennas are used in high frequency applications at frequency range of Ka-band and in wireless communication applications and satellite communication.

Trifrequency Reconfigurable Linear Irregular Array with Beam Deflection Capability in X/Ku/Ka-Bands

This paper proposes a trifrequency reconfigurable antenna (FRA), which can work in the X-band, Ku-band, and Ka-band, by controlling only two RF MEMS switches. The antenna element has a frequency ratio beyond 3 : 1 and provides a good candidate for the frequency reconfigurable antenna array, since the size of the antenna is reduced by loading multiple metal shorting holes between the antenna radiating surface and the ground plate, and the overall size is only 0.14λX × 0.35λX (λX is the free-space wavelength at 8.6 GHz). Based on the proposed FRA element, a 1 × 16 linear irregular frequency reconfigurable antenna array (FRAA) with beam deflection ability is designed, which effectively addresses the element spacing problem in the optimization of the array. In addition, the close-coupling in X-band and the grating lobe caused by the long distance of array element spacing in Ka-band are comprehensively considered. With uniform amplitude feeding network, the sidelobe level is below −15 dB under beam deflection. Moreover, both FRA elements and FRAA prototypes have been fabricated and measured to verify their superiority. Good agreements are obtained between simulated and measured results, which indicates that the antenna has potential application in the future multifrequency wireless communication and intelligent radar anti-interference fields.

High‐quality coplanar waveguide tunable band‐stop filter using defected ground structure and comb‐line resonator with radio frequency microelectromechanical system varactors

SummaryA new analog tunable Ka‐band band‐stop filter is proposed on high resistivity silicon (HRS) substrate using radio frequency microelectromechanical systems (RF MEMS) varactors for satellite and radar applications. The designed filter uses a λ/4 comb‐line resonator on the center line of a coplanar waveguide (CPW) with a new uncommon defected ground structure (DGS). Using the DGS in the proposed structure not only decreases the lateral size of the filter but also increases the quality factor. The tuning range of the proposed filter is 29.8–35.6 GHz with a maximum actuation voltage of 44.5 V and a band rejection between 37 and 45 dB. The quality factors of the designed filter in the up and down states of the MEMS varactors are 162 and 292, respectively. The equivalent circuit model of the filter is exactly extracted, and DGS dimensions are optimized. Based on the frequency simulation using ANSOFT HFSS 14, the insertion loss of the designed filter is about 0.51 dB in the 0–20 GHz range and 2 dB in the 0–15 GHz range in, respectively, up and down state of the bridge. The return losses are 0.51 and 0.33 dB at the center frequency for the up‐ and down‐state configuration of the bridge. A step‐by‐step fabrication process is also proposed for designing the band‐stop filter. High quality factor, small size, and improved structure are the advantages of the proposed design.

Reliability of RF MEMS switches at cryogenic (liquid He) temperatures

This paper reports on the reliability of RF MEMS switches operating in a cryogenic (<6 K) environment while monitoring the repeatability of their contact resistance (Rc) over time. Series DC-contact switches were actuated with a bipolar waveform then checked for stiction every 100 thousand contacts, and after every million cycles Rc was measured 100 times. Device lifetimes were limited to under 10 million contacts. The dominant failure mechanism is believed to be charging of the substrate underneath the electrostatic MEMS switch leading to permanent hold down of the device.

Coupled electromechanical and electromagnetic simulation of radio frequency microelectromechanical-systems (RF-MEMS) based on compact models approach

In this work, a modelling approach of complete RF-MEMS (MicroElectroMechanical-Systems for radio frequency) passives is discussed. The methodology takes into account both the non-linear electromechanical and the RF behaviour, and is suitable for being implemented and automated within a standard circuit simulator. The intrinsic electromechanical core is based on a structural hierarchical model library implemented in the VerilogA programming language, compatible with most commercial EDA (Electronic Design Automation) tools and circuit development environments. A wrapping lumped element network, extracted from S-parameters measured data, accounts for the electromagnetic RF behaviour of the MEMS device. The complete non-linear network can be hierarchically instantiated within a fully functional schematic environment for mixed domain design optimisation. The model is successfully validated against static and dynamic electromechanical and RF on-wafer measurements, using an optical interferometry profilometer. In particular, this paper discusses how the mentioned approach can be extended in order to include the effects due to the presence of a wafer-level package on the RF characteristics.

Metal contact RF MEMS switch design for high performance in Ka band

RF/microwave systems require switches to achieve tunability and reconfigurability. MEMS switches have always been a priority due to excellent RF performance (low insertion loss and high isolation). In this work, we present an RF Micro-Electro-Mechanical-System (RF MEMS) series switch that provides insertion loss less than 0.6 dB (on switch) and isolation better than 15 dB (off switch) at 40GHz. The designed switch consists of serpentine arms on the fixed end and two free-moving arms on another end. These free arms have individual contact points to overcome asperity problem during on state. To avoid self-actuation, bumps (0.6um) are used at the bottom side. This electrostatically actuated switch requires a pull-in voltage of 3.1V for 2.4 μm displacement in 67.14 μs time. The proposed switch is analysed in COMSOL software, and its RF characteristics are simulated in HFSS.

Design and performance analysis of hybrid SPDT RF MEMS switch

This paper presents the design and simulation of Hybrid type RF MEMS switch for satellite communication application. The Hybrid switch beam is having non-uniform meanders and holes. The gold material is used as a beam and CPW. The gap between the beam and dielectric is 3 μm. The design is based on the shunt and series configuration consisting of 2 capacitive switches and 2 Ohmic switches. The performance analysis is done by using the HFSS tool. The individual Ohmic switch having 31 dB isolation and capacitive switch having 67 dB isolation. The proposed Hybrid switch having 87 dB isolation when both switches are in the OFF state. During ON state, the switch shows the low insertion loss of − 0.18 dB and return loss of − 63 dB at 16 GHz.

A modified proposed capacitance model for step structure capacitive RF MEMS switch by incorporating fringing field effects

ABSTRACT This paper presents a new expression for the capacitance model based on ligament efficiency. The parallel plate capacitance is the first component derived based on the percentage of ligament efficiency and the second component which is fringing field capacitance is the combination of both existing Yang’s fringing field developed by the perforations and Meji’s capacitance model developed for fringing field due to sidewalls of parallel plates. The proposed model is the combination of three components and enhances accuracy to estimate the total capacitance. The proposed model contributes up to 10% and 2% of the fringing field in upstate capacitance and downstate conditions. The proposed capacitance model is validated by designing in FEM tool to obtain the deviation between the results and respective deviation is expressed as the percentage of error which results from 0.013% to 2.10% in up and downstate conditions. The error percentages are analysed for different ligament efficiencies to obtain the optimum value to enhance the performance of the switch.

Two element MIMO antenna with frequency reconfigurable characteristics utilizing RF MEMS for 5G applications

ABSTRACT This paper presents a novel two-element multiple input multiple output (MIMO) reconfigurable antenna that can be switched among 600 MHz, 1.8, 2.4, 3.5, and 5.5 GHz bands. The proposed antenna consists of two semi-circular ring-shaped strip-lines and a rectangular slot on the top conducting layer of the substrate and a U-shaped slot, etched on the bottom side of the substrate. Frequency reconfigurable characteristics have been achieved using single pole four throw radio frequency micro-electro-mechanical system switch. The switch has been installed in the ground slot. The dimensions of the proposed MIMO antenna are 32 × 98 × 1 mm3. Measured isolation greater than 15 dB has been achieved in the operating bands. The calculated envelop correlation coefficient is less than 0.04 and the diversity gain in the operating bands is greater than 9.8 dB.

Design and analysis of a RF MEMS shunt switch using U-shaped meanders for low actuation voltage

This paper presents the design and simulation of RF MEMS switch using uniform U-Shaped meanders. High isolation and low insertion loss are the main performance parameters enhanced by considering the inductive sections on the design and developing high capacitance using HfO2 as a dielectric medium. The inductive sections in the design help maintain the device at resonance. The proposed uniform U-shaped meanders lower the spring constant and reduce the Pull-in-voltage of the switch. The performance characteristics are observed by simulating the proposed switch in the electromechanics environment using the COMSOL FEM tool. The switch exhibits a low Pull-in-voltage of 5.2 V with a very low switching time of 23.1 µs. Total capacitance of 42.19 fF is formed during upstate which provides a low insertion loss of less than 0.1 dB. Capacitance of 19.11 pF during downstate provides high isolation of − 42.11 dB.

Design and Analysis of Reconfigurable DMTL phase Shifter for High Speed Applications by Mechanical Tuning

Tremendous advancement in the field of Radio-frequency were developed through Micro-fabrication techniques, these technologies miniaturize device in a micro-scale behavior for improved device performances. These technologies are developing rapidly due to its distinct features and wide usage in various applications ranging from switches to sensing devices. The principal behind this work is to build a MEMS based Reconfigurable DMTL phase shifter based on RF MEMS switch with improved device phenomenon like switching speed, low actuating voltage, losses and stress factors. The RF switch is build in a series behavior through co-planar waveguides. Generally switching speed is a major concern in RF MEMS devices because of the presence of the actuating elements within the structure which in turn hinders the device ability to function. The phase shifter designed helps in improving the overall switching speed of the device without electrical or dimension alternation of the device. In this paper, we are implementing a PUSH PULL based RF MEMS reconfigurable switch which was structurally altered based on triangular cantilevers in order to enhance the device switching speed. This would develop and enable better application in terms of reconfigurable phase shifter which can be operated at the wider bandgap applications. Even the resonant frequency enhancement was made which provokes an increase of 13% in terms of the switching speed.

RF MEMS switches, switching networks and phase shifters for microwave to millimeter wave applications

This work presents design, fabrication and measurements of RF MEMS metal-contact switches, switching network and phase shifters. The complete work is broadly divided into three parts. The first part concentrates on the metal-contact switch functionalities in terms of mechanical behaviour, electrical behaviour, transient analysis, linearity, power handling, temperature, S-parameter and reliability. All these switch performances are critically evaluated for developing high-performance and reliable MEMS switch. Different single-pole-multi-throw (SPnT) switching networks are also designed and tested where n varies from two to sixteen. Next part concentrates on the design and development of narrow-band (500 MHz) MEMS digital phase shifters (2- to 5-bit) driven by an electrostatic actuation. Next and last phase of this work deals with a reconfigurable MEMS digital phase shifter using a push–pull-type beam topology. The utility of this beam design is validated and tested on a simple DMTL configuration where 11 push–pull bridges are used in a periodic placement. Finally, a modified version of the push–pull actuator is used to design a frequency reconfigurable 5-bit phase shifter over a wide band of spectrum of 10–25 GHz. The concept of the frequency reconfiguration is clearly mentioned and validated with exhaustive measurement process. In addition, a low-cost module is developed using gold-coated brass material to observe optimum device performance for end-user applications and two phase shifters are tested over large cycles including power handling, temperature stability and qualification testing such as 3-axis vibration.

A Survey to Assess the Quality of the Data Obtained by Radio-Frequency Technologies and Microelectromechanical Systems to Measure External Workload and Collective Behavior Variables in Team Sports.

Electronic performance and tracking systems (EPTS) and microelectromechanical systems (MEMS) allow the measurement of training load (TL) and collective behavior in team sports so that match performance can be optimized. Despite the frequent use of radio-frequency (RF) technology (i.e., global positioning navigation systems (GNSS/global positioning systems (GPS)) and, local position systems (LPS)) and MEMS in sports research, there is no protocol that must be followed, nor are there any set guidelines for evaluating the quality of the data collection process in studies. Thus, this study aims to suggest a survey based on previously used protocols to evaluate the quality of data recorded by RF technology and MEMS in team sports. A quality check sheet was proposed considering 13 general criteria items. Four additional items for GNSS/GPS, eight additional items for LPS, and five items for MEMS were suggested. This information for evaluating the quality of the data collection process should be reported in the methods sections of future studies.

Development of a low stress RF MEMS double-cantilever shunt capacitive switch

In this paper, a novel RF MEMS shunt capacitive switch with application in the Ka frequency band is proposed. The spring design and the step structure added to the beam succeeded in improving the performance of the switch and reducing the stress which results in extended life-time of the switch. Also, by optimally reducing the gap between the dielectric and the beam (without problems such as self-actuation), the actuation voltage of the switch is significantly reduced. Electromechanical and scattering parameters analysis have been done by using COMSOL Multiphysics and HFSS software, respectively. The actuation voltage of the proposed device is 9.2 V. Since the aluminum has a lower mass compared to gold, an aluminum beam has been used in the switch. Desirable scattering parameters at the resonance frequency of 33.5 GHz have been obtained which include insertion loss of − 0.3 dB and return loss of − 18 dB. The high isolation of − 57 dB verifies the improved performance of the switch. Finally, as another innovation in this paper, the effect of inductor and capacitor presence in the input of transmission line is investigated. This analysis has been done by using ADS. Results of the circuit analysis presented in this paper, help the MEMS switch designers to understand the realistic switch behavior before fabrication which considerably saves cost and time.

Thin Film Encapsulation for RF MEMS in 5G and Modern Telecommunication Systems

In this work, SiNx/a-Si/SiNx caps on conductive coplanar waveguides (CPWs) are proposed for thin film encapsulation of radio-frequency microelectromechanical systems (RF MEMS), in view of the application of these devices in fifth generation (5G) and modern telecommunication systems. Simplification and cost reduction of the fabrication process were obtained, using two etching processes in the same barrel chamber to create a matrix of holes through the capping layer and to remove the sacrificial layer under the cap. Encapsulating layers with etch holes of different size and density were fabricated to evaluate the removal of the sacrificial layer as a function of the percentage of the cap perforated area. Barrel etching process parameters also varied. Finally, a full three-dimensional finite element method-based simulation model was developed to predict the impact of fabricated thin film encapsulating caps on RF performance of CPWs.

Effect of Stress on Pull-in Voltage of RF MEMS SPDT Switch

RF MEMS switches are well known to exhibit performance superior to solid-state devices. However, electromechanical issues, such as repeatability and higher pull-in voltage, are a matter of concern. MEMS switches generally consist of metallic beams which curl up or down based on stresses in the structure. Stress-induced curling-up phenomenon, in such structures, increases the gap between the actuating electrode and the freely suspended metallic structure which in turn increases the pull-in voltage. This article focuses on simulations and curve fitting to analyze the effect of stress on pull-in voltage. The pull-in voltage of the switch is proportional to stress, and accordingly, its dependence on in-built stress and Young's modulus is analyzed. In addition to mechanical analysis, RF response of the single pole double throw (SPDT) switch is discussed as a case study. Measured stress and pull-in voltage of the SPDT switch is 50 MPa and 16 V. In the presence of stress, the curled-up cantilever switch shows measured isolation better than 31 dB for dc to 10-GHz range.

Design and characterization of RF MEMS capacitive shunt switch for X, Ku, K and Ka band applications

In this paper, we present the design and development of a Radio Frequency Micro-Electro-Mechanical-Systems (RF-MEMS) capacitive shunt switch based on a fixed-fixed beam configuration for X (8–12 GHz), Ku (12–18 GHz), K (18–26 GHz) and Ka (26–40 GHz) band applications. The design parameters for RF switch have been taken into consideration based on in-house standard 6” CMOS foundry. Silicon substrate with high resistivity (ρ > 8 kΩ-cm, εr = 11.8, and tanδ = 0.01) has been utilized for the realization of MEMS switch. The device demonstrates the pull in voltage of 22.78 V. The measured return loss, insertion loss and isolation are better than 20 dB, 0.5 dB and 25 dB respectively, over the entire frequency band (0–40 GHz).The electromechanical and electromagnetic analyses of 3D structure were performed using Finite Element Method (FEM) & Method of Moments (MoM) based full wave simulators. Design and simulation data was further validated by measured results during DC and RF characterization of the devices.

Design, optimization and analysis of reconfigurable antenna using RF MEMS switch

This paper presents the design, optimization and analysis of a novel radio-frequency micro electromechanical system (RF MEMS) switch for reconfigurable antenna. The proposed antenna operates at frequency band from 4.5 to 12.5 GHz. The antenna is created by reconfiguring its size using a rectangular patch and an inverted U shaped patch via RF MEMS switch. A series metal to metal contact RF MEMS switch is designed and optimized for low actuation voltage with adequate switching speed and excellent RF characteristics. The design of RF MEMS switch is simulated using CoventorWare and RF analysis is performed on Ansys HFSS software. Pull in voltage obtained for the switch is 5.7 V with switching time of 38.7 μs. The isolation obtained is better than − 20 dB for DC to 25 GHz. Insertion loss is less than − 0.4 dB for DC to 60 GHz and return loss is also better than − 23 dB for DC to 60 GHz. Further the designed reconfigurable antenna is simulated using Ansys HFSS software. The antenna is reconfigurable at 4.5 GHz, 8.6 GHz, 9 GHz, 12.3 GHz, 12.4 GHz and 12.5 GHz for different switch positions.

A Switchable High-Performance RF-MEMS Resonator with Flexible Frequency Generations

Resonators with multi-frequency generations at the device-level are highly desired in the future multi-band, reconfigurable, and compact wireless communications. In this work, a switchable radio frequency micro-electro-mechanical system (RF-MEMS) resonator with multiple electrodes is presented. The resonator is designed to operate at the whispering gallery modes (WGMs). Simultaneous excitations of the second to seventh modes with high Q values are implemented within a single device using a pair of electrodes for driving and sensing. For effective multi-frequency excitations, the electrode span angle is optimized. The frequencies of the 37 μm and 18 μm-radius resonators range from 53 MHz to 176 MHz and 112 MHz to 366 MHz, respectively. The Q values in each mode are over 104. Moreover, with the multi-electrode configurations, the specific mode can be enhanced with other modes suppressed. A more than 6 dB improvement of the spectrum peak is realized and the high Q values are maintained. A comprehensive theory is built up to clarify the driving/sensing principles under different electrode configurations. Furthermore, the air damping is found to have a significant effect on Q values for resonator with high stiffness vibrating in all the WGMs. The Q values in vacuum have at least two times improvement. The high-performance switchable resonator could dramatically reduce the power consumption, simplify the processing circuits, and occupy less footprint, which has great potential applications in future advanced RF front end systems.