Tunable lowpass and bandpass lumped-element filters employing barium-strontium-titanate (BST)-based capacitors are presented A new metallization technique is used, which improves the quality factor of the tunable BST capacitors by a factor of two The lowpass filter has an insertion loss of 2 dB and a tunability of 40% (120-170 MHz) with the application of 0-9 V DC bias The bandpass filter (BPF) has an insertion loss of 3 dB and a tunability of 57% (176-276 MHz) with the application of 0-6 V DC The third-order intercept point of the BPF was measured to be 19 dBm with the application of two tones around 170 MHz

Voltage-controlled RF filters employing thin-film barium-strontium-titanate tunable capacitors

This paper presents a ruthenium metal-contact RF microelectromechanical system switch based on a corrugated silicon oxide/silicon nitride diaphragm. The corrugations are designed to substantially reduce the influence of the fabrication-induced stress in the membrane, resulting in a highly insensitive design to process parameter variations. Furthermore, a novel multilayer metal-contact concept, comprising a 50-nm chromium/50-nm ruthenium/500-nm gold/50-nm ruthenium structure, is introduced to improve the contact reliability by having a hard-metal surface of ruthenium without substantial compromise in the contact and transmission-line resistances, which is shown by theoretical analysis of the contact physics and confirmed by measurement results. The contact resistance of the novel metallization stack is investigated for different contact pressures and is compared to pure-gold contacts. The contact reliability is investigated for different dc signal currents. At a measurement current of 1.6 mA, the Ru-Au-Ru contacts have an average lifetime of about 100 million cycles, whereas the Au-Au contacts reach 24 million cycles only. For larger signal currents, the metal contacts have proven to be more robust over the Au-Au contacts by a factor of ten. The measured pull-in voltage is reduced significantly from 61 V for flat diaphragm to 36 V for corrugated diaphragm with the introduction of corrugation. The measured RF isolation with a nominal contact separation of 5 mum is better than -30 dB up to 4 GHz and still -21 dB at 15 GHz, whereas the insertion loss of the fully packaged switch including its transmission line is about -0.7 dB up to 4 GHz and -2.8 dB at 15 GHz.

A Ruthenium-Based Multimetal-Contact RF MEMS Switch With a Corrugated Diaphragm

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.

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

Radio frequency (RF) microelectromechanical systems (MEMS) have been pursued for more than a decade as a solution of high-performance on-chip fixed, tunable and reconfigurable circuits. This paper reviews our research work on RF MEMS switches and switching circuits in the past five years. The research work first concentrates on the development of lateral DC-contact switches and capacitive shunt switches. Low insertion loss, high isolation and wide frequency band have been achieved for the two types of switches; then the switches have been integrated with transmission lines to achieve different switching circuits, such as single-pole-multi-throw (SPMT) switching circuits, tunable band-pass filter, tunable band-stop filter and reconfigurable filter circuits. Substrate transfer process and surface planarization process are used to fabricate the above mentioned devices and circuits. The advantages of these two fabrication processes provide great flexibility in developing different types of RF MEMS switches and circuits. The ultimate target is to produce more powerful and sophisticated wireless appliances operating in handsets, base stations, and satellites with low power consumption and cost.

/pdf/rf-mems-switches-and-integrated-switching-circuits-2vsihyk7su.pdf

RF MEMS Switches and Integrated Switching Circuits

Two novel lateral metal-contact radio-frequency microelectromechanical system (RF MEMS) switches are reported. These switches are implemented with quasi-finite ground coplanar waveguide (FGCPW) configuration and actuated by applying electrostatic force on a high-aspect-ratio cantilever beam. It is demonstrated that the insertion loss of the switch is less than 0.2 dB up to 15 GHz and the isolation is higher than 20 dB up to 25 GHz. An RF model of the switches is used to analyse the effects of the switch design parameters and RF performance. The optimization of the switch mechanical design is discussed where the threshold voltage can be lower than 25 V. The lateral switches are fabricated by deep reactive ion etching (DRIE) process on a silicon-on-insulator (SOI) wafer with shadow mask technology.

https://nocweba.ntu.edu.sg/laq_mems/journal%20papers/2005/Low-loss%20lateral%20micromachined%20switches%20with%20frequencies%20from%20DC%20to%2025%20GHz.pdf

Low-loss lateral micromachined switches for high frequency applications

A serial combination of two different RF MEMS switch types is presented. This combination of an ohmic contact switch (toggle switch) and a capacitive coupling switch yields extreme broadband operation and exhibits low insertion loss ( 50 dB from DC to 50 GHz).

Serial combination of ohmic and capacitive RF MEMS switches for large broadband applications

Key elements for switching matrices are reported. Single RF-MEMS toggle switches yield an insertion loss of 0.2 dB @ 30 GHz and an isolation of 25dB @ 30 GHz. Shielded RF crosses for routing the signal path in the switching matrix yield an insertion loss of 0.75dB @ 20 GHz in the under-cross path and 0.6 dB (simulated) in the over-cross path with an isolation higher than 40dB between under- and over-cross path. Double 90 degree bends with compensated air-bridges show an insertion loss of less than 0.1dB up to 20 GHz.

RF-MEMS components for broadband applications

A scaled, smaller version of the recently published toggle switch, an extremely broad band and highly linear ohmic RF MEMS switch for a frequency range from DC to 50 GHz, is presented. The electromagnetic simulation, the fabrication process, and measured results of the small toggle switch are given. The switch in its smaller geometry inherits the outstanding RF performances which could even be extended with an insertion loss of 0.95 dB and an isolation of 16 dB up to 50 GHz. These measurement results are in good agreement with the simulation. Power measurements results are in good agreement with the simulation. Power measurements (2 W) in the frequency range from 8 to 18 GHz did not show a self actuation of the switch.

W. Simon

Papers

Serial combination of ohmic and capacitive RF MEMS switches for large broadband applications

RF-MEMS components for broadband applications

A very compact RF MEMS switch for frequencies up to 50 GHz