A novel torsional RF MEMS capacitive switch design on silicon substrate is presented. The optimized switch topology such as reduction in up-state capacitance results in insertion loss better than ź0.1 dB till 20 GHz. Off to on state capacitance ratio is also improved by 18 fold and isolation is better than ź43 dB at 9.5 GHz. The achieved on state return loss is ź38 dB as compared to ź21 dB at 9.5 GHz. An optimized reduction in contact area and use of floating metal layer increases the switching speed from 56 to 46 μsec. It also increases the switch reliability by alleviating the stiction.

Design of novel compact anti-stiction and low insertion loss RF MEMS switch

This paper presents a low insertion loss capacitive shunt RF-MEMS switch. In the presented design, float metal concept is utilized to reduce the capacitance in up-state of the device. Float metal switch shows an insertion loss <0.11 dB, a return loss below 26.27 dB up to 25 GHz as compared to 0.81 dB insertion, 8.67 dB return loss for the conventional switch without float metal. OFF state response is same for the both devices. Further pull-in voltage of 12.75 V and switching time of 69.62 µs have been observed in case of the conventional switch whereas device with float metal have 11.75 V and 56.41 µs. Improvement of around 2.5 times in bandwidth and 4 times in input power has been observed without self actuation, hold down problem. The designed switch can be useful at device and sub-system level for multi-band applications.

Design and investigation of a low insertion loss, broadband, enhanced self and hold down power RF-MEMS switch

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.

/pdf/comprehensive-study-on-rf-mems-switches-used-for-5g-scenario-rnbaryy3b1.pdf

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

This paper presents the design, fabrication, and characterization of shunt type ohmic RF MEMS switches actuated by piezoelectricity. Since the proposed RF MEMS switches are actuated by piezoelectricity, they can be operated at an extremely low operation voltage of 5 V with a negligible power consumption of less than 0.1 μW. The proposed switches are primarily composed of piezoelectric cantilever actuators, a contact electrode and coplanar wave transmission lines suspended over the substrate. Unlike existing series type switches, the RF signal line of the shunt type ohmic switches is directly connected from the RF input port to the RF output port without any discontinuity, and their contact electrode is interconnected to all grounds. In this work, we consider three different types of RF MEMS switches in order to find the best geometry. The RF MEMS switch with one piezoelectric cantilever (Type-A) shows very poor isolation characteristic although it has better insertion loss than the others. The other two RF switches, which employ four piezoelectric cantilevers (Type-B and Type-C), differ in terms of the configuration of the cantilevers and the centered contact electrode. One has a centered contact electrode of square shape (Type-B), while the contact electrode of the other switch has a diamond shape (Type-C). They show relatively good isolation characteristics even at a very high frequency of 20 GHz, since the use of four piezoelectric cantilevers can generate a sufficiently large contacting force between the contact electrode and the RF signal line. The two fabricated RF MEMS switches have isolations of −23.0 and −24.0 dB, respectively, at an operation voltage of 5 V and a frequency of 20 GHz. The power-handling capability of the proposed RF MEMS switches increases to 1.4 W when an Iridium thin film coating is applied on the gold contact electrode.

Development of shunt type ohmic RF MEMS switches actuated by piezoelectric cantilever

A radio frequency micro-electro-mechanical system (RF-MEMS) phase shifter based on the distributed MEMS transmission line (DMTL) concept towards maximum achievable phase shift with low actuation voltage with good figure of merit (FOM) is presented in this paper. This surface micro-machined analog DMTL phase shifter demonstrates low power consumption for implementation in a Ka-band transmit/receive (T/R) module. The push–pull-type switch has been designed and optimized with an analytical method and validated with simulation, which is the fundamental building block of the design of a true-time-delay phase shifter. Change in phase has been designed and optimized in push and pull states with reference to the up-state performance of the phase shifter. The working principle of this push–pull-type DMTL phase shifter has been comprehensively worked out. A thorough detail of the design and performance analysis of the phase shifter has been carried out with various structural parameters using commercially available simulation tools with reference to a change in phase shift and has been verified using a system level simulation. The phase shifter is fabricated on the alumina substrate, using a suspended gold bridge membrane with a surface micromachining process. Asymmetric behaviour of push–pull bridge configuration has been noted and a corresponding effect on mechanical, electrical and RF performances has been extensively investigated. It is demonstrated 114° dB−1 FOM over 0–40 GHz band, which is the highest achievable FOM from a unit cell on an alumina substrate reported so far. A complete phase shifter contributes to a continuous differential phase shift of 0°–360° over 0–40 GHz band with a minimum actuation voltage of 8.1 V which is the highest achievable phase shift with the lowest actuation voltage as per till date on the alumina substrate with good repeatability and return loss better than 11.5 dB over 0–40 GHz band.

https://iopscience.iop.org/article/10.1088/0960-1317/22/12/125006/pdf

Design and development of a surface micro-machined push-pull-type true-time-delay phase shifter on an alumina substrate for Ka-band T/R module application

In this paper, we present a new type of rf MEMS switch with low actuation voltage and high isolation, for high rf power and reliability applications in telecommunication. ‘Symmetric toggle switch’ (STS) is based on push–pull mechanism and utilizes torsion springs and levers, placed symmetrically and transverse to CPW line. The switches designed for 8–14 GHz applications have analytically calculated and FEM simulated actuation voltages in the range of 8–10 V. The simulated insertion loss and isolation for the devices are 0.25 and 35 dB, respectively, at 10 GHz. The fabrication process and preliminary experimental results are also presented.

Laura del Tin

Papers

Symmetric toggle switch—a new type of rf MEMS switch for telecommunication applications: Design and fabrication