Xiong Jijun

A novel micro-accelerometer with adjustable sensitivity based on resonant tunnelling diodes

Resonant tunnelling diodes (RTDs) have negative differential resistance effect, and the current-voltage characteristics change as a function of external stress, which is regarded as meso-piezoresistance effect of RTDs. In this paper, a novel micro-accelerometer based on AlAs/GaAs/In0.1Ga0.9As/GaAs/AlAs RTDs is designed and fabricated to be a four-beam-mass structure, and an RTD-Wheatstone bridge measurement system is established to test the basic properties of this novel accelerometer. According to the experimental results, the sensitivity of the RTD based micro-accelerometer is adjustable within a range of 3 orders when the bias voltage of the sensor changes. The largest sensitivity of this RTD based micro-accelerometer is 560.2025 mV/g which is about 10 times larger than that of silicon based micro piezoresistive accelerometer, while the smallest one is 1.49135 mV/g.

Enhancing the Robustness of the Microcavity Coupling System

A novel method to enhance the robustness of the microcavity coupling system (MCS) is presented by encapsulating and solidifying the MCS with a low refractive index (RI) curable UV polymer. The encapsulating process is illustrated in detail for a typical microsphere with a radius of R about 240μm. Three differences of the resonant characteristics before and after the package are observed and analyzed. The first two differences refer to the enhancement of the coupling strength and the shift of the resonant spectrum to the longer wavelength, which are both mainly because of the microsphere surrounding RI variation. Another difference is the quality factor (Q-factor) which decreases from 7.8×107 to 8.7×106 after the package due to the polymer absorption. Moreover, rotation testing experiments have been carried out to verify the robustness of the package MCS. Experimental results demonstrate that the packaged MCR has much better robust performance than the un-package sample. The enhancement of the robustness greatly promotes the microcavity research from fundamental investigations to application fields.

Pressure effects in AlAs/InxGa1−xAs/GaAs resonant tunnelling diodes for application in micromachined sensors

This paper reports the current?voltage characteristics of [001]-oriented AlAs/InxGa1?xAs/GaAs resonant tunnelling diodes (RTDs) as a function of uniaxial external stress applied parallel to the [110] and the [10] orientations, and the output characteristics of the GaAs pressure sensor based on the pressure effect on the RTDs. Under [110] stress, the resonance peak voltages of the RTDs shift to more positive voltages. For [10] stress, the peaks shift toward more negative voltages. The resonance peak voltage is linearly dependent on the [110] and [10] stresses and the linear sensitivities are up to 0.69?mV/MPa, -0.69?mV/MPa respectively. For the pressure sensor, the linear sensitivity is up to 0.37?mV/kPa.

Wireless contactless pressure measurement of an LC passive pressure sensor with a novel antenna for high-temperature applications

In this paper, a novel antenna is proposed for high-temperature testing, which can make the high-temperature pressure characteristics of a wireless passive ceramic pressure sensor demonstrated at up to a temperature of 600 °C. The design parameters of the antenna are similar to those of the sensor, which will increase the coupling strength between the sensor and testing antenna. The antenna is fabricated in thick film integrated technology, and the properties of the alumina ceramic and silver ensure the feasibility of the antenna in high-temperature environments. The sensor, coupled with the ceramic antenna, is investigated using a high-temperature pressure testing platform. The experimental measurement results show that the pressure signal in a harsh environment can be detected by the frequency diversity of the sensor.

Piezoresistive properties of resonant tunneling diodes

A measurement system was designed and established to test the piezoresistive properties of resonant tunneling diodes (RTDs). The current-voltage characteristic shifts of RTD at different stress states were detected. The experimental results demonstrate that the piezoresistive sensitivity of RTD is larger than 1 × 10−8 Pa−1. To accurately represent the piezoresistive properties of RTD, the current-voltage characteristic coherence of the same RTD was tested. According to the experimental results, the largest relative resistance shift of an RTD in the same measurement environment is less than 3%, of which 1% is caused by the testing apparatuses.

A novel MEMS SiC pressure sensor for high-temperature application

This paper designs a SiC (Silicon Carbide) non-contact capacitive pressure sensor for high-temperature application. The sensor is proposed to operate at high temperature environment due to its SiC -glass paste- SiC sandwiched structure. Mechanical performance of the sensor is verified by finite element analysis software and its MEMS process flow is also presented in detail. The SiC capacitive chip and external inductor coils composed a LC circuit for the purpose of extraction and measurement of pressure signal. The conversion between external pressure signal and resonance frequency signal of LC circuit is successfully achieved by wireless passive pressure measurement technology, providing a new way to solve the nonlinear test of variable-gap capacitive pressure sensor. Test result shows that resonant frequency and applied pressure have an inverse relationship under a range of 0-200kPa with a high sensitivity of 10.6 kHz/kPa. The design idea of the novel sensor provides a reference for the development of high-temperature pressure measurement.

Modulating and driving system for the application of microelectromechanical system infrared source array

A problem demanding to be solved in the development of microelectromechanical system (MEMS) IR source array has been the driving circuit and system. A method that can achieve the requirements of high driving power, high output efficiency, high voltage precision, voltage compensation, and deep frequency modulation for driving and modulating a MEMS IR source array was proposed. A liner DC steady voltage integrated circuit ADP3336 is used to drive the source array directly with a programmable compensation module ensuring the precision of radiation peak wavelength. And a FPGA as the control core of the system modulates the frequency and width of the driving pulse to control the array coding pattern. The engineering value of the system would be increased with the application of the MEMS IR source.

Design of Wireless Coupling Signal Transmission Antenna and Impedance Matching

In this work, an extremely compact antenna is designed and used for wireless coupling signal transmitting. This antenna is constituted by a planar spiral inductance and a capacitance. The inductance is designed with 10 turns, 0.5mm turn width, 0.5mm turn spacing and 21mm inner diameter. Calculate the planar inductance parameter and use ADS (Advanced Design System) software to match the antenna impedance at the center frequency of 8.54MHZ. Structuring the impedance matches circuit. Compare the voltage or impedance changes before and after the antenna impedance matching, and optimize the antenna impedance matching network.

Design and test of high load piezoelectricity actuator

Considering the high overload application of the pizeoceramic in the self-adapted bullet, a new piezoceramic actuator based on d33 structure is designed. In this paper, aluminum foil substrate and piezoceramic multilayer are introduced. According to the FEA simulation, this structure can afford a high load to 2000 g, which is definitely enough for the bullet application. The fabrication process was designed in the paper and a sample is fabricated followed it. The sample is packed in an elastic metal frame for the calibration. According to the test, this actuator can sustain a shock of more than 20000 g, and it work well for the actuation purpose when the voltage is applied.

A Cantilever Accelerometer Based on Resonant Tunneling Diode

This paper presents a GaAs piezoresistive accelerometer based on the GaAs/AlAs Resonant Tunneling Diode (RTD). As the sensing unit, the resonant tunneling thin films are designed and integrated on the cantilever. In order to decrease the parasitic capacitance and control the thickness of the cantilever accurately, RTD and seismic mass are successfully fabricated by airbridge and control hole technique separately. The static pressure experiments prove that the piezoresistive coefficient of resonant tunneling device change with the bias voltage. Under 0.75 V bias voltage, the microaccelerometer shows the sensitivity of 87 muVV -1 g -1 and non-linearity is less than 0.2% in the positive difference resistance region.