Key Engineering Materials Vols. 609-610

Abstract: Presented is a control system that is designed for an electromagnetic vibrating ring gyroscope. Three functions are realized in this control system. First, fixed amplitude of the drive-mode is guaranteed by using a variable gain control (VGC). Test result shows that the stability of the drive-mode amplitude is about 0.4% in the range of-40°C~80°C. Second, suitable drive-frequency is set up. And experimental result indicates that the suitable drive-frequency should be set between the drive-and sense-mode resonance frequencies, which results in a superior sensitivity. Third, regulation module is employed to further improve the performance.

Abstract: A new readout system based on LC resonant sensor is presented. The readout system consists of a reader coil inductively coupled to the LC resonant sensor, a measurement unit, and a PC post processing unit. The measurement unit generates an output voltage representing the sensor resonance, converts the output voltage to numerical form, and saves the converted digital data. The PC post processing unit processes the digital data and calculates the sensor's resonance frequency. The readout system enables wireless interrogation and its accuracy is exemplified by an experimental system. The experimental system can detect the resonant frequency of sensor automatically and effectively. The experimental results are presented for different sensor resonance frequencies with various sensor capacitance values and show good agreement with the theoretical results. The entire design is simple, easy to use, and widely applicable for applications where the coupling distance between sensor and reader coil is variable.

Abstract: In this paper, in order to enhance resolution and guarantee the stability of the micro-gyroscope, a high-resolution lowpass sigma-delta modulator is proposed. It employs single-loop fourth-order and full differential structure. The simulated result on the Simulink platform shows that the SNDR is 105.4dB and the effective number of bits (ENOB) is 17.22bits. The entire circuits are implemented with 0.5μm CMOS process. The simulated result on Cadence shows that the SNDR is 99.7dB. The modulator operates at a sampling frequency of 25.6MHz and the signal bandwidth is 100kHz with 128 oversampling ratio (OSR). The dynamic range (DR) is 120 dB approximately and the SNDR changes linearly with the input level.

Abstract: The design and fabrication of MEMS capacitive differential pressure sensor is reported. Silicon membrane is used as movable electrode. Gold metal film on glass is used as fixed electrode. Anodic bonding is used to bond together the silicon and glass to form the capacitive pressure sensor. The measurement capacitance of the sensors is 5.37 pF at an applied pressure of 0 kPa and 7.26 pF and the full operating range of 40 kPa.The ratio of changed to initial capacitance was 0.35. The error of the MEMS capacitive pressure sensor is less than 4‰ full-scale(FS) by using quadratic curve fitting which can meet most application requirements.

Abstract: This paper describes a wireless, passive humidity sensor, based upon an inductor-capacitor circuit. An inductor with a dual-metal structure is employed to reduce the size of the chip and decrease the complexity of the process. This paper analyzes the shortcomings of conventional sensors and gives a novel structure to overcome these disadvantages, and also use ADS to simulate and verify the feasibility of the new structure. Finally this paper presents a detail fabrication process of this novel sensor. According to the wireless applications, the LC resonant frequency of the LC circuit was designed at 30 ~ 150 and 350~450MHz.

Abstract: QRS is widely used in many areas and the driving voltage is the key to the proper functioning of QRS. In this paper, a new mixmode driving circuit is presented.The circuit uses both square wave and sine wave to drive QRS which can adopt their good points and avoid their shortcomings. The simulation results show that in this circuit, the oscillation is stabilized within 8ms and the range of frequency is 11.68kHz ~11.69kHz. The distortion factor of the driving circuit is 3.22% which makes the circuit much more satisfying.

Abstract: The output signal of the free-drive three-axis MEMS gyroscope used in Spinning Projectiles contains rolling is sine period signal. In order to demodulate the yawing and pitching angular rates, extracting the fringe phase information is needed. It is difficult to realize the phase demodulation of single signal. To solve this problem, reference signal is provided. The phase of the gyroscope is extracted by computing the phase difference. Then, three methods of phase difference measurement are introduced and simulated by MATLAB. According to the signal feature, the contrastive analysis of measurement error is made and the maximal precision of measuring method for phase difference is obtained. The last part is the analysis of performance.

Abstract: Based on the OPAC (Optical Properties of Aerosols and Clouds) database, the impact of 8 typical aerosol types on the skylight polarization sensitive is researched. By combining the impact of cloud, the correction between aerosol and the polarization sensitive spectral of insects is analyzed. It can predict the polarization properties of different areas and provide the theoretical basis for the application of bionic micro-nanopolarization sensor.

Abstract: A wireless and power-free pressure sensor system capable of real time in vivo gastrointestinal pressure monitoring has been developed. This system contains a sensor unit and a detection unit. Based on mutual inductance detection mechanism, the sensor is featured with simple device structure and therefore low cost. The packaged sensor unit was tested. Results obtained from experiment demonstrated that this sensor has a sensitivity of 0.2115 kHz / kPa within a pressure range-10~30 kPa. The in vivo testing result not only indicates a period of 2 contractions per minute peristalsis of rabbit stomach but also validates the feasibility of this real time wireless gastrointestinal pressure monitoring system.

Abstract: This paper reports a readout system for a piezoresistive accelerometer which is fabricated by LTCC thick-film process technology. The authors first introduce a LTCC compatible design of this new kind of accelerometer, which is based on piezoresistive phenomenon. As the performance of the accelerometer circuitry is affected by temperature, a readout system is introduced for compensating the temperature drift and the non-linearity of this piezoresistive accelerometer by using the MAX1452 processor. The authors give the principles of the temperature compensation and the executive processes. The readout system also includes a ZigBee wireless transmission system and a real-time curve display window. Some tests on the system are carried out and the results manifest that the readout system designed in this paper is workable.