Suspended Square Research Articles

Lamé Resonator Integrated With Chevron-Shaped Thermal Actuators to Improve Motional Resistance and Temperature Stability

This paper presents a capacitive bulk mode resonator operating in Lamé mode, where the motional resistance and temperature stability are enhanced by implementing a set of chevron-shaped thermal actuators to reduce the transducer air gaps. The chevrons are heated using micro-heaters that are integrated on the actuator. The device is fabricated in the PiezoMUMPS standard microfabrication process by MEMSCAP. The measured resonant frequency for the fabricated device was observed to be 17.9 MHz. It has been experimentally shown that the transducer air gap can be reduced from 2.5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu m$</tex-math> </inline-formula> to 0.5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu m$</tex-math> </inline-formula> by applying a heater voltage of 2.7 V at atmospheric pressure. In the proposed resonator, the transmission loss can be reduced by 8.54 dB when the actuators are biased at 1.8 V in vacuum, as opposed to when the actuator is off. Under these conditions, the thermal actuators each consume 39 mA. In addition, the implemented thermal actuators can function as integrated heaters that increase the temperature of the suspended square structure to compensate for ambient temperature variations. As such, applying a voltage of 1.8 V in vacuum reduces the resonant frequency from 17.95 MHz to 17.91 MHz, while applying a voltage of 2.6 V at atmospheric pressure reduces the resonant frequency from 17.97 MHz to 17.86 MHz.2022-0188

A Lorentz force magnetometer based on a piezoelectric-on-silicon square-extensional mode micromechanical resonator

In this letter, we present a Lorentz force magnetic field sensor based on a thin-film piezoelectric-on-silicon (TPoS) CMOS-compatible resonator for the detection of an out-of-plane (perpendicular to the plane of fabrication) magnetic field. We here exploit the fundamental breathing mode of vibration in a suspended square plate, which is commonly referred to as the square-extensional (SE) mode. The symmetric stress profile of the SE mode avails stresses in the two orthogonal in-plane axes to be effectively coupled into a charge output through the piezoelectric transducers. This in turn enhances the output motional current from the device, which effectively determines the responsivity of the device. In this context, the responsivity has been defined as a ratio of output motional current to the external magnetic field, which has been further normalized against the input reference current of the device. The reported device has recorded a responsivity of 6950 ppm/T (μA/A.T) at a resonant frequency of 5.28 MHz and a reasonable mechanical quality (Q) factor of 1056 in air.

A 2.4-GHz dual polarized suspended square plate rectenna with inserted annular rectangular ring slot

This research has proposed a dual polarized suspended square plate rectenna for RF-to-DC conversion at the 2.40–2.50 GHz frequency band. The proposed dual polarized antenna yields improved isolation with an annular rectangular ring slot etched in the square radiating plate. The proposed antenna could achieve >40.00 dB isolation and >8.00 dBi gain with unidirectional radiation. The proposed SMS7630-based rectifying circuits were measured and could realize the maximum conversion efficiency of 25.98% (1.57 V) with a 3.00 kΩ resistor and 2.00 mW input RF power of a signal generator. On integration, the experimental vertical polarization rectenna was capable of achieving the maximum conversion efficiency of 21.86% (14.20 mV) at the 0.5 m distance and 0.00015.00 mW/cm2 input power density. The proposed dual polarized rectenna can receive the input RF power density of arbitrary polarization with obtained average conversion efficiency of 14.97% (10.50 mV) at the 0.5 m distance of wireless local area network (WLAN) system. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:164–173, 2016.

A Microstrip-Line-Fed Suspended Square Slot Microstrip Antenna for Circular Polarization Operations

A microstrip line-fed suspended square slot antenna with parasitic patch is presented. The proposed antenna is excited by a microstrip line feed placed at the bottom side of the substrate. The antenna geometry gets excitation via EM coupling. In this structure circular polarization (CP) is also obtained with suspended air gap and CP frequency can be switched between 4.5GHz to 5.5GHz. Thus, a 3 dB axial ratio bandwidth of about 4.32% is obtained. This structure exhibitsimpedance bandwidth, which is over 20.83%. The antenna was optimized with Ansoft’s HFSS software and was validated through a prototype. Measured results fairly agree with the simulated data.

A Planar UWB Diversity Antenna

A planar dual-port diversity antenna, operating with broadside and/or conical radiation patterns in H-planes, is presented for ultrawideband (UWB) applications. The proposed antenna consists of a suspended square patch with a thick stem underneath. A broadband differential feeding strip is used to feed the square patch. The measured gain for the broadside mode is 8.4-10.3 dBi from 3.1 GHz to 5.2 GHz (50.6%), and the conical mode 3.2-5.1 dBi from 3.1 GHz to 4.9 GHz (45%). The measured reflection coefficients (|S 11|, |S 22|) are less than -10 dB over the frequency ranges and the isolation |21| between the two ports is greater than 13.5 dB. The operation of the differential feeding strip on the antenna is discussed. Both pattern diversity and partial polarization diversity are achieved for this antenna.

탄소섬유를 이용한 압력센터 제작 및 특성평가

This paper reports fabrication and characterization of a pressure sensor using a pitch-based carbon fiber. Pitch-based carbon fibers have been shown to exhibit the piezoresistive effect, in which the electric resistance of the carbon fiber changes under mechanical deformation. The main structure of pressure sensors was built by performing backside etching on a SOI wafer and creating a suspended square membrane on the front side. An AC electric field which causes dielectrophoresis was used for the alignment and deposition of a carbon fiber across the microscale gap between two electrodes on the membrane. The fabricated pressure sensors were tested by applying static pressure to the membrane and measuring the resistance change of the carbon fiber. The resistance change of carbon fibers clearly shows linear response to the applied pressure and the calculated sensitivities of pressure sensors are 0.25 ~ 0.35 and 61.8 Ω/kΩㆍbar for thicker and thinner membrane, respectively. All these observations demonstrated the possibilities of carbon fiber-based pressure sensors.