Key Engineering Materials Vols. 562-565

Abstract: In this paper, a low-distortion fourth-order bandpass sigma-delta (ΣΔ) modulator is proposed based on a switched-capacitor resonator which employs double-sampling technique to relax the requirements for circuits and reduce opamp power consumption and chip area. The modulator is based on the low-distortion low pass ΣΔ modulator. The system level simulation results compare between the low-distortion architecture and the traditional one is given. The full differential circuit applying two-path technique is implemented with TSMC0.18µm CMOS process. It achieves a peak SNR (signal-to-noise ratio) of 85.9dB and DR (dynamic range) of 91dB with 200 kHz bandwidth centered at 20MHz which are better than the conventional bandpass ΣΔ modulator.

Abstract: Anti-violent rocket on small UAV creatively combines the anti-riot shell with the UAV,utilizing the theory of rocket lanching,realizing that Anti-violent Shell is launched far in the sky.It is significant for CAPF to realize variety of targets battle in the emergency and mission. This paper focuses on sumulation and testing of anti-violent rocket engine on Small UAV,and the flight test-fired experimental of engine is carried on with control system,which demonstrates its feasibility.

Abstract: The experiment of stimulating fluorine to desorb from fluorinated graphene was carried out in order to make clear the dynamical mechanism of the electron-stimulated desorption (ESD) of fluorine. X-ray photoelectron spectroscopy (XPS) with an electron beam gun accessory was used not only to stimulate fluorine to desorb, but also to characterize the concentration of fluorine after ESD. The concentration of fluorine dropped quickly following electron beam irritation. The desorption cross section of fluorine is about 1.5×10-17 cm2. It was also found that electron beam with low current density did not damage the structure of fluorinated graphene. These results confirm that it is feasible to fabricate all graphene electronics by ESD technology.

Abstract: To improve the performances under low speed wind, a wind energy harvester similar to harmonicas was proposed. The harvester mainly includes a cuboid chamber and a cantilevered beam. The front wall of the chamber is opened as the air entrance and a rectangular hole is opened on the sidewall as the exit. The cantilever composed of a piezoelectric sheet and a flexible beam was fixed onto the sidewall of the chamber near the exit. Experimental results show that the width and height of the chamber significantly affect critical wind speed and output power, respectively. The initial attack angle of the cantilever has important influence on the critical wind speed. Blunt body at the air entrance could remarkably decrease the critical wind speed. For a prototype with a 60 mm×20 mm×13 mm chamber, the length of the cantilever of 30 mm and the length of the piezoelectric sheet of 8 mm, the measured maximum output power is 1.1 mW under 17 m/s wind.

Abstract: In order to test the dynamic performance of MEMS devices accurately, the laser Doppler vibrometer was adopted to test the frequency characteristics and surface vibration of the MEMS scanning mirror. The measuring formulas of the object motion velocity and displacement were derived. A kind of MEMS scanning mirror was tested using the established optical testing system. The measurement results show that the resonance frequency characteristic and the transient response characteristic is 269Hz and 60ms respectively which are consistent with the theoretical analysis. The method has significant reference value to the application of the laser Doppler technique.

Abstract: In recent year, the sensitivities of atomic spin devices are improved greatly with the realization of spin exchange relaxation free (SERF) regime. Usually the SERF regime is realized using orthogonal beams scheme, i.e. one pump beam to polarize the atoms and the other orthogonal probe beam to measure the polarization. Due to the requirement of four optical windows for the atomic vapor cell, the orthogonal beams scheme has difficulties for micro fabrication. In this paper, we research a new scheme for SERF realization using only one beam, which facilitates the micro fabrication greatly. Furthermore, the fabrication processes of the MEMS atomic vapor cell with two out-of-plane optical windows are designed and performed. In the end, the possibility of increasing the relaxation time by nanotechnology is discussed.

Abstract: A compact and versatile nanomanipulation platform and its dirve-control system are being developed. This nanomanipulation sytem is aimed to handle nanowires (NWs) and fabricate nanostructures by NWs in a Scanning Electron Microscope (SEM). The excellent performance of the compact manipulator developed with corase and fine positioning in one unit has been demonstrated, which shows that the resolution is 8 nm and the steps are from 50 nm to 0.8 μm. For the power supply of the manipulator, a three-output driver is designed with a high-power integrated operational amplifier based on a mixed approach of voltage control and current control. The planar push-and-lift handling of NWs is carried out by the use of two tips to demonstrate the capability of the nanomanipulation sytem inside SEM.

Abstract: This paper presents a novel high performance W-band MEMS duplexer for digital signal transceiver applications. The design of duplexer filters follows the insertion loss method with a Chebyshev polynomial to meet the desired spectral responses. The insertion loss and return loss of the optimized duplexer are -0.3dB and -18dB respectively, while the isolation between two pass bands is -55dB. A micro-fabrication process is designed based on MEMS technology. The deep reactive ion etching (DRIE) is used for high-aspect-ratio filter cavity mold structure. Micro-electroforming, plastic embossing, and electroplating techniques are used for low-cost and high-precision mass production program for the duplexer. Fabrication error tolerance is analyzed and it is reasonable to control the shift of frequency and return loss in the range of 0.05GHz and 2dB respectively with the designed fabrication process based on MEMS technology. It proves that the proposed micromachining fabrication technique is suitable for high performance W-band waveguide filter and duplexer design in terms of stability of RF performance.

Abstract: Bonding-deep reaction ion etching (DRIE) is a standard microelectromechanical system (MEMS) fabrication technique, especially for widely-applied comb-capacitor microdevices. Being the key structure in the comb-capacitor devices, long and narrow suspended beams suffer a serious heat transfer problem during their releasing in the fabrication because of the high heat flux input and the large thermal resistance. Temperature increment of the micro beam in the DRIE releasing, especially in the unavoidable over etching stage, may cause serious problem, even lead to a failed etch. This work introduced a generalized thermal design model to estimate the possible temperature increment of microstructure in DRIE. The preliminary results indicated that this model was able to capture the basic trend of temperature variation with the geometrical parameters in a comb-capacitor MEMS device during its DRIE releasing.

Abstract: This paper describes the research status of MEMS spring used in fuze. For the Nickel planar S-form micro-spring, according to its application environment and design requirements, the length of the straight beam was taken as the only variable to study the variation of the micro-spring dynamic stiffness under high impact load. These researches can provide some reference views to design applications and reliability analysis of micro-spring used in the munitions, and also can lay the foundation for the response characteristics of the micro-scale elastic components under impact load.