Li-Feng Wang

A Novel Three-State RF MEMS Switch for Ultrabroadband (DC-40 GHz) Applications

Design, fabrication, and measurement results of a lateral dc-contact RF microelectromechanical systems switch for ultrabroadband applications are presented in this letter. The switch is driven by a bidirectional cascaded electrothermal actuator, which can generate larger displacements and contact forces at two directions than traditional electrothermal actuators. Because of this bidirectional actuator, the proposed switch can not only realize the off-state to on-state shifting, but also provide an additional deep off-state. The proposed switch is fabricated by MetalMUMPs process, and measurement results show that the insertion loss is less than -0.5 dB and the initial isolation is better than -22.5 dB at 0-40 GHz range. At the deep off-state, the isolation better than -30 dB can be achieved at the whole frequency range 0-40 GHz. The measurement results agree well with the theory and design.

Simultaneous Remote Sensing of Temperature and Humidity by LC-Type Passive Wireless Sensors

This paper presents an integrated wireless passive sensor for remotely monitoring both temperature and relative humidity. The sensor consists of a coil and a capacitor to form an inductor-capacitor (LC) resonant circuit, which oscillates electrically at its resonant frequency. The inductor was a singlelayer planar spiral copper inductor and the capacitor was fabricated by the silicon-on-glass process, which utilizes graphene oxide films as the sensing material. The change of the capacitance due to environmental humidity variation shifts the resonant frequency, while environmental temperature affects the resistance and capacitance of the LC circuit and changes the resonant frequency and quality factor. By monitoring the real portion magnitude maximum of the impedance and the resonant frequency for the sensor, it is possible to get the capacitance and resistance from which the temperature and humidity can be extracted. The results presented here show that the sensitivity of the passive wireless sensor is about -17.80 kHz/%RH and 7.32 Q/%RH at 25 °C from 55%RH to 95%RH, and it is about -7.69 kHz/°C and 6.27 Ω/°C at 65%RH from 10 °C to 40 °C.

Lateral Contact Three-State RF MEMS Switch for Ground Wireless Communication by Actuating Rhombic Structures

A laterally actuated three-state RF microelectromechanical systems switch for ground wireless communication applications is proposed, fabricated, and tested. By electrostatically actuating a rhombic beam, the proposed switch can not only realize the off-state to on -state shifting but also provide an additional deep off state. The switch was fabricated by silicon on glass (SOG) bulk silicon micromachining. The 2- μm-thick gold electroplating layers were introduced in the SOG process to enhance the performance of lateral contacts. The off-state and deep- off-state isolations of the prototype switch were measured to be -67.6 dB and - 72.2 dB at 0.9 GHz and -48.3 dB and -53.0 dB at 6 GHz, respectively. The measured insertion loss is -0.13 dB at 0.9 GHz and -0.38 dB at 6 GHz, respectively. The measured actuation voltage is 78 V. The switching-on and switching-off response times are 72 and 64 μs, respectively.

A New Method for Real-Time Measuring the Temperature-Dependent Dielectric Constant of the Silicone Oil

This paper presents a new method for real-time measuring the temperature-dependent relative dielectric constant and the thermal expansion coefficient of the silicone oil by using a low-cost microelectromechanical systems (MEMS) structure. The relative dielectric constant of the silicone oil can be obtained by measuring the capacitance of an MEMS temperature sensing structure, and the silicone oil is used as the temperature sensing material of the capacitive structure. A processing circuit on a printed circuit board is designed to complete the measurement. A theoretical model is constructed to describe the behavior of the relative dielectric constant and the thermal expansion coefficient over a certain range of temperatures. Preliminary experimental results show that the variation of the relative dielectric constant and the thermal expansion coefficient versus temperature could be detected real timely and simply based on this method.

A high performance microwave equalizer based on MEMS technology

The theory, design, fabrication and measurements of a MEMS equalizer for adjusting the microwave signals are presented. The novelty of the equalizer is the CPW line with released signal and ground sections based on the MEMS technology. In this method the work frequency can be achieved higher and the minimal insertion losses can be greatly reduced due to the dielectric losses. The MEMS equalizer is fabricated by MetalMUMPs process. The experimental results show that reflection losses of the MEMS equalizer are below -17dB at the whole frequency range, the minimal insertion losses are around 1dB at 21GHz frequency point and the maximal insertion losses are around 2.7dB at 26.8GHz frequency point. The experimental results agree well with the theory and the simulation.

An in-situ measurement method for thermally induced packaging stress in distributed RF MEMS Phase Shifters

In this paper, an in-situ measurement method for thermally induced packaging stress in the distributed RF MEMS phase shifters is presented. Base on the analytical relation among the actuation voltage, the stiffness coefficient of and the resident stress on the beams of the devices, the thermally induced packaging stress from the die-attaching process in the device can figure out by measuring the increased value of the actuation voltage for offsetting the deviation of the phase shift of the device after the packaging process. A case study is conducted to demonstrate the principle and procedure of the proposed measurement method. And the variation of the actuation voltage can also be used as a bias voltage to offset the deviation of the phase shift characteristic of the device due to the thermally induced packaging stress.