DC-contact Switch Research Articles

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.

Superconducting Tunable Microstrip Gap Resonators Using Low Stress RF MEMS Fabrication Process

A Nb superconducting tunable microstrip gap resonator has been designed and fabricated with low stress Au RF MEMS dc-contact switches. The resonator can be tuned in four states from 12–15 GHz. Simulations show that the resonator $Q$ is highly sensitive to the contact resistance of the MEMS when the switches are actuated. Measurements confirm that the $Q$ degrades from 200 to 50. RF performance of the resonator is investigated at cryogenic (4 K) temperatures while the Nb is superconducting.

Extensive performance evaluations of RF MEMS single-pole-multi-throw (SP3T to SP14T) switches up to X-band frequency

This work presents wide range of compact and reliable single-pole-multi-throw (SPMT) radio frequency (RF) microelectromechanical system (MEMS) switches where the M (output) varies from 3 to 14 throws. The single dc-contact switch dimensions are 0.144 mm × 0.29 mm which are fabricated on 635 µm alumina substrate using a surface micromachining process. SPMT switching networks demonstrate a measured return loss of more than 14 dB, a worst case insertion loss of ~1.76 dB and isolation of ~14.5 dB up to 12 GHz. The maximum area of the fabricated SPMT switch is ~1.2 mm2. The SPMT switches are capable of handling 1 W of RF power up to >1 billion cycles at 25 °C, and sustained even up to >80 million cycles with 0.5 W at 85 °C. To the best of our knowledge, this is the first reported wide range of MEMS SPMT switches and their respective performance evaluations in the literature that has undergone extensive measurement stages.

Finite element modeling of a Ti based compact RF MEMS series switch design for harsh environment

Regardless of the excellent RF characteristics that microelectromechanical switches possess in variety of high frequency applications, some of these application areas require switches that could possibly withstand harsher environments like high temperature or high thermal stresses. This paper presents the finite element modeling of a compact RF MEMS DC contact switch design based on titanium material to withstand in such conditions. The switch is designed with meanders on all sides to increase the elastic recovery forces. The proposed switch dimensions are very compact with the total surface area of 0.1 mm$$^2$$2. The modelled switch is optimized for L-band that results in high isolation of 52 dB and very low insertion loss of 0.007 dB at 2 GHz with low actuation voltage of 18.5 V.

Multiple Timescales and Modeling of Dynamic Bounce Phenomena in RF MEMS Switches

Electrostatically operated RF-MEMS switches are known to suffer from discrete switch bounce events during switch closure that increase wear and tear and lead to increased switching times. Here, we use laser Doppler vibrometer to analyze the switch response of three types of cantilevered dc-contact switches at a 200 ns time resolution. We find that bounce events are multiple time scale events with distinct motion occurring at 10-1 and 101 s timescales in effect high frequency bounces within a bounce. To understand the origin of this effect, we develop a multiple eigenmode model of a cantilever switch with electrostatics, repulsive and adhesive contact forces, and rarefied gas damping and find that the high frequency bounce arises from the transient excitation of the 2nd eigenmode of the cantilever structure of the RF-MEMS switch. This phenomenon not only describes the multiple time scales involved in bounce events, but also shows that the transient excitation of the second mode leads to complex drum roll like dynamics, leading to a series of closely spaced impacts in each actuation cycle. A careful study of the dependence of the phenomenon on contact stiffness and adhesion shows how the landing pad stiffness, adhesion, and actuation voltage in dc contact switches can increase or diminish repeated impacts during actuation.

A Novel Stiff Membrane Seesaw Type RF Microelectromechanical System DC Contact Switch on Quartz Substrate

This paper proposes a novel RF MEMS dc-contact switch with stiff membrane on a quartz substrate. The uniqueness of this work lies in the utilization of a seesaw mechanism to restore the movable part to its rest position. The switching action is done by using separate pull-down and pull-up electrodes, and hence operation of the switch does not rely on the elastic recovery force of the membrane. One of the main problems faced by electrostatically actuated MEMS switches is the high operational voltages, which results from bending of the membrane, due to internal stress gradient. This is resolved by using a stiff and thick membrane. This membrane consists of flexible meanders, for easy movement between the two states. The device operates with an actuation voltage of 6.43 V, an insertion loss of -0.047 dB and isolation of -51.82 dB at 2 GHz.

The Design and Modeling of a Reconfigurable Inset-Fed Microstrip Patch High Gain Antenna for Wireless Sensor Networks

In this paper, we designed a tunable microstrip patch antenna using RF MEMS switches. The design and simulation of the antenna were performed using a high frequency structure simulator(HFSS). The antenna was designed for use in the ISM band and either operates at 2.4 GHz or 5.7 GHz achieving -10 dB return-loss bandwidths of 20 MHz and 180 MHz, respectively. In order to obtain high efficiency and improve the ease of integration, a high resistivity silicon(HRS) wafer on a glass substrate was used for the antenna. The antenna achieved high gains: 8 dB at 5.7 GHz and 1 dB at 2.4 GHz. The RF MEMS DC contact switches were simulated and analyzed using ANSYS software.

RF MEMS Switches and Integrated Switching Circuits

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.

Influence of The Sticking Effect on The Contact Resistance of a MEMS DC-Contact Switch

An improved model of the contact resistance in a MEMS DC-contact switch is presented and the sticking effect is included. In this model, the JKR theory is used to determine the sizes of contact spots and the electrical contact theory is used to estimate the contact resistance. The relationship between the contact resistance and the applied force has been investigated in different cases for a common Au-Au contact. The results suggest that the contact resistance is related to the applied force, the number of asperities, and the surface energies of contact materials. However, the height distribution of asperities has little influence on the contact resistance. The comparison between the improved model and the measurements that have been reported suggests the sticking contact model is more reasonable than the elastic contact model especially at low applied forces.

FULLY INTEGRATED PIEZOELECTRIC RF MEMS IN-LINE DC CONTACT SWITCHES WITH ULTRA-LOW VOLTAGE OPERATION

ABSTRACT In this paper, ultra-low voltage operated piezoelectric RF MEMS in-line dc contact switches with serial and shunt configurations have been realized by using silicon bulk micromachining technologies for advanced mobile handset applications. The developed RF MEMS in-line dc contact switches are comprised of four piezoelectric cantilever actuators with an Au contact metal electrode and a suspended Au signal transmission line above the silicon substrate. These dc contact switches perform a ‘make and break’ operation in an electrical path with metal-metal contacts and hence show good insertion loss and exhibit excellent linearity. The measured operation dc bias voltages are ranged from 2.5 to 4 volts by varying the thickness and the length of the piezoelectric cantilever actuators, which are well agreed with the simulated results. The measured isolation and insertion losses of the switch with serial configuration are −43 dB and −0.21 dB (including parasitic effects of the silicon substrate) at a frequency of 2 GHz and an actuation voltage of 3 volts, while the switch with shunt configuration has −18 dB and −0.8 dB at the same frequency range. However, the switch with shunt configuration has constant isolation characteristics without any degradation as operation frequencies increase. These both switches also have excellent performance characteristics over the higher frequency regime at the ultra low voltage operation.