Low-loss RF MEMS Research Articles

Design and Development of a Low Insertion Loss RF MEMS Shunt Ohmic Switch

Design and Development of a Low Insertion Loss RF MEMS Shunt Ohmic Switch

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.

Optimum Electromagnetic Modelling of RF MEMS Switches

Radio frequency microelectromechanical systems (RF MEMS) switch technology may have the potential to replace semiconductor technology in future communication systems as well as communication satellites, wireless and mobile phones. RF MEMS switches are being developed for low insertion loss, high isolation loss and high linearity that are required over a broad frequency band application. In wireless mobile communication systems, microstrip transmission lines (t-line) have received attention for their attractive benefits such as low profile, light weight, and easy fabrication. The present work has thus been to explore the design and modelling of low loss RF MEMS switches implemented in a microstrip discontinuity t-line configuration. The electromagnetic modelling of an RF MEMS switch with a microstrip line is presented with a simple analytical model to determine the scattering parameters. This study shows that an RF MEMS switch with a microstrip t-line provided less than 0.01 dB–0.05 dB insertion loss for 50 GHz frequency. Moreover, there is an isolation loss of 50 dB over frequencies up to 50 GHz frequency. This low insertion and high isolation loss in the single beam RF MEMS switch with a microstrip discontinuity t-line contributes to configuring a low loss transmission line for RF communication.DOI: http://dx.doi.org/10.5755/j01.eie.24.5.21842

A novel design of a low-voltage low-loss T-match RF-MEMS capacitive switch

This paper presents a novel design, optimization and analysis of capacitive radio frequency (RF) micro-electromechanical system (MEMS) switch. The design incorporates a novel membrane and beams' structure with two short high-impedance transmission-line (T-line) sections added on either side of the switch (namely T-match switch) to improve its RF performance, while maintaining low-actuation voltage. The short high-impedance T-line section has narrower width and higher impedance than the coplanar waveguide (CPW)'s signal line, behaves as series inductor to compensate the switch's up-state capacitance and provides excellent matching at the design frequency. This high-impedance T-line section was designed, simulated and optimized using finite-element-modelling (FEM) tool of electromagnetic (EM) simulator of AWR Design EnvironmentTM. The optimized T-line section's width and length is 10 µm and 70 µm, respectively. The RF-MEMS switch is actuated by electrostatic force with low-actuation voltage of 2.9 V, has maximum von Mises stress of 13.208 MPa which is less than aluminium's yield stress and can be operated in robust conditions. Compared to the normal capacitive RF-MEMS switch, this T-match capacitive RF-MEMS switch with two sections of optimized high-impedance T line has improved the performance of return loss and insertion loss, at switch-on state, by 45.83% and 55.35%, respectively; while at the switch-off state, the isolation is increased by 24.05%; only the switch-off return loss is degraded by 11.7% but the value (ź 0.5519 dB) is still located in the range of design specifications. The RF-MEMS switch's actuation time was simulated to be ~ 27 µs with amplitude of 5 V up-step voltage.

Power efficient, low loss and ultra-high isolation RF MEMS switch dedicated for antenna switch applications

We present a new ultra-high isolation RF MEMS latching switch with ultra-low power consumption dedicated to antenna switch applications in multiband and multi-standard transceivers. Power management of the switch is done by integrating latching actuators in switch structure. Actuation voltage of the switch is 5V and the switch consumes a power of around 131mW for 50 µs while transition to ON or Deep-OFF states. The switch is modeled and its operation is comprehensively analyzed. The switch has an IIP3 of 127dBm and power handling of up-to 6W without causing stiction. The insertion loss of the switch is −0.5dB up to 20GHz. When the switch is OFF, the input and output are isolated with −50dB for up to 20GHz. At the Deep-OFF state, the switch is connected to the GND and isolation reaches −130dB up to 20GHz. These results are from FEM simulations and has not been verified by experiment.

SiGe BiCMOS high‐gain and wideband differential intermediate frequency amplifier for W‐band passive imaging single‐chip receivers

This thesis presents solutions and studies related to the design of reconfigurable and wideband receiver circuits for system-on-chip (SoC) radiometer front-ends within the millimetre-wave (mm-wave) range. Whereas many of today’s mm-wave front-ends are bulky and costly due to having discrete RF components, single-chip receiver modules could potentially result in a wider use for emerging applications such as wireless communication, short range radar and passive imaging security sensors if realised with adequate performances and at a lower cost. Three main topics are considered in this thesis, monolithic integration of low-loss RF-MEMS (Dicke) switch networks and switched LNAs in MMIC/RFIC foundry processes, designs of SiGe wideband (IF) amplifier and broadband power detectors up to W-band (75-110 GHz).Low-loss and high isolation GaAs and SiGe RF-MEMS switch networks were designed and characterised for the 30-110 GHz range. A GaAs MEMS Dicke switch network has a measured minimum loss of 1 dB and maximum isolation of 19 dB at 70-96 GHz, respectively, making it a potential candidate in Dicke switched radiometer receivers. Furthermore, single-chip 30 GHz and W-band MEMS Dicke switched LNA designs have been realised for the first time in SiGe BiCMOS and GaAs mHEMT processes, respectively.For a targeted 94 GHz passive imaging application two different receiver topologies have been investigated based on direct-detection and direct-conversion (heterodyne) architectures. An optimised detector design fabricated in a 0.13 μm SiGe process achieves a more wideband input matching than earlier silicon W-band detectors and is competitive with reported III-V W-band detectors in terms of a higher responsivity and similar NEP.A SiGe 2-37 GHz high-gain differential (IF) amplifier design achieves a more wideband matching and an order of magnitude higher linearity than a recent single-ended SiGe LNA. The SiGe IF amplifier was integrated on-chip with a power detector in a 5-35 GHz IF section. Their broadband properties compared with other IF amplifier/detector RFICs, make them suitable for W-band down-conversion receivers with a larger pre-detection bandwidth and improved sensitivity. The experimental results successfully demonstrate the feasibility of the SiGe 5-35 GHz IF section for high performance SoC W-band radiometers using a more wideband heterodyne receiver architecture.

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

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.

An Electronically-Scanned 1.8–2.1 GHz Base-Station Antenna Using Packaged High-Reliability RF MEMS Phase Shifters

This paper presents the first 4-element base-station antenna that is passively scanned using low-loss RF MEMS phase shifters. The design is based on packaged RF MEMS SPDT switches, which are capable of handling Watts of RF power with high reliability. The results agree very well with simulations and show pattern scanning to 9° with a measured gain of 8.6-8.3 dB at 2 GHz. The array is capable of handling 5-10 W of power with no distortion.

RF MEMS Capacitive Switches for Wide Temperature Range Applications Using a Standard Thin-Film Process

In this paper, the design, fabrication, and measurements of a capacitive RF microelectromechanical systems (RF MEMS) switch with very low sensitivity to thermal stress is presented. The switch is built by thin-film technology (0.8-μm Au) and shows <;50-mV/°C variation in the pull-down voltage at 25 °C-125 °C. The effects of the residual biaxial stress and stress gradients are studied in detail and the final switch design is very tolerant to a wide range of stress. The switch exhibits excellent RF and mechanical performances, and a capacitance ratio of about 51-57 (Cu = 54-66 fF, Cd = 3.1 - 3.4 pF) is reported. The mechanical resonant frequency and quality factor are fο = 105 - 115 kHz and Qm ≈ 8, respectively, with a measured switching time of about 3-3.8 μs. The applications areas are in low-loss RF MEMS, phase shifters, and reconfigurable networks.

High-power handling capability of low complexity RF-MEMS switch in Ku-band

A low complexity, low-loss RF-MEMS switch suited for high-power applications is presented. The switch was originally designed for small-signal operation in the Ku-band and is able to handle at least 6 W RF power in the hot-switching mode. In addition to small- and large-signal S-parameter measurements, a brief explanation of its high-power properties is given.

Development of a large-force low-loss metal-contact RF MEMS switch

We improved the large restoration force of a radio-frequency microelectromechanical system (RF MEMS) switch, which had been a challenge in the practical application of RF MEMS switches, by adopting a non-linear spring system for the electrostatic actuator. When an electrostatic actuator with a movable electrode area of 1.4 mm 2 was driven at a voltage of 24 V, analysis showed a restoration force three-fold greater than that of conventional linear spring systems and a stable signal on–off control action. It was also established from simulation and observation of the RF characteristics in a plastic mold package that the actuator has the ability comparable to or exceeding the characteristics of positive intrinsic negative (PIN) diodes and GaAs metal-semiconductor field-effect transistors (MESFETs).

Packaging for RF MEMS devices using LTCC substrate and BCB adhesive layer

In this paper, a packaging method utilizing an LTCC (low temperature co-fired ceramic) substrate and a BCB (benzocyclobutene) adhesive layer has been developed for RF MEMS devices, and the RF performance and characteristic parameters of the package have been evaluated. LTCC substrates have good RF characteristics in high-frequency applications, and via feedthroughs can be easily incorporated during the manufacturing process. In this paper, an LTCC substrate is used as a capping wafer to reduce the complex processes for vertical interconnections. A layer of BCB, in the form of sealing rims, is used as an adhesive to bond the MEMS substrate with the LTCC cap due to the excellent properties of BCB as a packaging material. A CPW (coplanar waveguide) line has been fabricated on a quartz substrate and packaged to demonstrate the performance of the proposed packaging method. After forming the CPW lines, a 28 µm thick BCB layer is patterned by double-coating photolithography for an adhesive bonding. On the backside of the LTCC cap, a 150 µm deep cavity is formed to improve the RF characteristics. The CPW and the contact pad are connected electrically through the silver via-post in the LTCC substrate by screen-printed silver epoxy. The RF characteristics of the CPW line have been measured before and after packaging. The insertion loss of a bare CPW is 0.047 dB at 2 GHz and 0.092 dB at 20 GHz. After packaging, the insertion loss of the packaged CPW is 0.091 dB at 2 GHz and 0.312 dB at 20 GHz. A leak test has been performed using both IPA (isopropyl alcohol) soaking and the He leak tester. Most of the samples show no leakage for the IPA test, and a measured leak rate of 10−8 atm cc s−1 for the He leak test. In addition, the shear strength of the package was measured to be 25–35 MPa. From the experimental results, we showed the feasibility of a low-loss RF MEMS package from dc to 20 GHz with acceptable package performances.

Performance of low-loss RF MEMS capacitive switches

'This letter details the construction and performance of metal membrane radio frequency MEMS switches at microwave and millimeter-wave frequencies. These shunt switches possess a movable metal membrane which pulls down onto a metal/dielectric sandwich to form a capacitive switch. These switches exhibit low loss (<0.25 dB at 35 GHz) with good isolation (35 dB at 35 GHz). These devices possess on-off capacitance ratios in the range of 80-110 with a cutoff frequency (figure of merit) in excess of 9000 GHz, significantly better than that achievable with electronic switching devices.