电桥测量基础

电桥是精密测量电阻或其他模拟量的一种有效的方法。本文介绍了如何实现具有较大信号输出的硅应变计与模数转换器（ADC）的接口．特别是∑一△ADC。当使用硅应变计时．它是一种实现压力变送器的低成本方案。[编者按]     

A novel semiconductor capacitive sensor for a single-chipfingerprint sensor/identifier LSI

We describe a new semiconductor capacitive sensor structure and the fabrication process for a single-chip fingerprint sensor/identifier LSI in which the sensor is stacked on a 0.5-μm CMOS LSI. To ascertain the influence of the fabrication process and normal usage on the underlying LSI, sensor chips were subjected to an electrostatic discharge (ESD) test, mechanical stress test, and unsaturated pressure cooker test (USPCT). ESD tolerance is obtained at the value of ±3.0 kV. To investigate mechanical stress, we carried out a tapping test. The sensor is immune to mechanical stress under the condition of 10⁴ taps with the strength of 1 MPa. A multilayer passivation film consisting SiN under polyimide film provides protection against contamination such as water. Thus, under USPCT conditions of 130°C, 80% humidity, and 48 h, the chips were not degraded. The tests confirm that the proposed sensor has sufficient reliability for normal identification usage     

石墨烯/聚吡咯/聚苯胺复合材料的制备与电容性能

超级电容器是一种绿色储能节能器件,其性能主要是由电极材料所决定的.以疏松的石墨烯(GR)为模板,先后以吡咯(Py)和苯胺(ANi)为单体,采用两步原位聚合法制备了具有"三明治"结构的石墨烯/聚吡咯/聚苯胺(GR/PPy/PANi)复合材料,探索了原料比对复合材料结构、微观形貌、电化学性能的影响.研究表明,Py和ANi分...     

基于NIOS的I2C总线接口芯片AT24C16读写的实现

简要介绍了I^2C总线的基本结构和规范、I^2C总线接口芯片的基本工作原理、NIOS自带的PIO模块寄存器的读写原理和该PIO模块所使用的相应软件接口子程序，着重介绍了在NIOS上实现对12C接口芯片AT24C16读写时序的模拟和程序的编写实现。     

C 波段全固态T / R 组件设计

C波段星载合成孔径雷达(SAR)系统是应用于海洋目标监视的有力手段之一.基于T/R组件的有源相控天线可靠性高,成为现阶段星载SAR雷达的研究热点,其对T/R组件的需求特点包括:高效率、低功耗、重量轻、费用低、高幅度相位稳定性和高可靠性.文中介绍了最新研制的四通道C波段星载T/R组件,采用微波多芯片组件技术,T/R组件通道间距为1/4波长,其输出功率大于22W,噪声系数2.3dB,接收增益大于23dB,功率附加效率大于23％,重量小于200g.     

Ni/C纤维提高Ni/Al球形颗粒导电硅橡胶性能研究

为减少球形Ni/Al填充量并提高Ni/Al填充导电硅橡胶屏蔽效能,选取Ni/C纤维加入到此种导电橡胶中,并从导电性、屏蔽性能方面对其进行评价。实验发现Ni/C纤维的掺杂可以提高导电橡胶的导电性及屏蔽性能。当总颗粒填充量为130 phr时,掺杂纤维使导电橡胶的体积电阻率从1010Ω·cm降至1.4Ω·cm;当总颗粒填充量为240 phr时,在1.0~2.5 GHz的频段内,其屏蔽效能在90 d B以上,而未经过掺杂的仅能超过60 d B。利用面心立方堆垛结构模型计算颗粒间最小距离,结果发现导电橡胶的渗流阈值与颗粒最小间距有较为明显的相关性。     

Design and characterization of novel read-out systems for a capacitive DNA sensor

This paper presents novel read-out electronic systems for a fast DNA label-less detection. The capacitive shift due to the hybridization effect is monitored by means of a charge sensitive amplifier and a differential stage. The systems provide an A/D conversion and an evaluation of the capacitive shift amount with a resolution of 11 bit. The read-out solutions demonstrate the ability to identify a 0.01% variation on the capacitive value of the sensor. The investigated techniques are suitable for monolithic systems or for a micro-fabricated array of sensors.     

Boundary element modeling of a capacitive probe for in situ soilmoisture characterization

There has been a need for accurate numerical modeling of a capacitive probe dedicated to the in situ characterization of soil moisture in measuring the dielectric permittivity of the soil. The objectives of the author's modeling were to understand the quantitative response of the probe, to optimize the shape of the probe, and to enable accurate calibration. In comparison with other numerical methods (such as the finite element method), the boundary element method appears straightforward and economical. The author presents a generalized version of this method in the case of an axisymmetrical geometry within the quasi-static limit. Numerical results are discussed and compared with the approximation of a lumped circuit     

一种智能卡读写器的设计与实现

智能卡是一类具备较强的逻辑和数据处理能力的IC卡，目前在很多领域都有着非常广泛的应用。智能卡读写器则主要是为相关用户提供一个使用智能卡的功能平台，是智能卡应用和开发中的关键环节之一。介绍了一种智能卡读写器的设计和实现，提出了其硬件组成和相关软件协议方面的有关解决方案，详细分析了读写器与用户端之间的应用接口，并对其与COS端的命令接口进行了讨论。实践证明，读写器结构可靠、性能稳定，特别在通用性和批数据处理方面表现突出。     

Development of a miniature pressure transducer for biomedical applications

Miniature absolute pressure transducers are needed for biomedical implant applications. The design parameters are: 1) sensitivity, 2) size, 3) hysteresis, 4) temperature coefficient, 5) long-term stability, and 6) biocompatibility. The present devices cannot meet all the requirements, particularly in size, long-term stability, and biocompatibility. The results of a development program on implantable and indwelling pressure transducers are reported with emphasis on the study of long-term stability and reproducibility associated with reduced size. The sensor is a resistive bridge diffused on a     

Noise analysis and characterization of a sigma-delta capacitive microaccelerometer

This paper reports a high-sensitivity low-noise capacitive accelerometer system with one micro-g//spl radic/Hz resolution. The accelerometer and interface electronics together operate as a second-order electromechanical sigma-delta modulator. A detailed noise analysis of electromechanical sigma-delta capacitive accelerometers with a final goal of achieving sub-/spl mu/g resolution is also presented. The analysis and test results have shown that amplifier thermal and sensor charging reference voltage noises are dominant in open-loop mode of operation. For closed-loop mode of operation, mass-residual motion is the dominant noise source at low sampling frequencies. By increasing the sampling frequency, both open-loop and closed-loop overall noise can be reduced significantly. The interface circuit has more than 120 dB dynamic range and can resolve better than 10 aF. The complete module operates from a single 5-V supply and has a measured sensitivity of 960 mV/g with a noise floor of 1.08 /spl mu/g//spl radic/Hz in open-loop. This system can resolve better than 10 /spl mu/g//spl radic/Hz in closed-loop.     

Preparation and characterization of conductive polypyrrole/kaolinite composites

Conductive polypyrrole (PPy)/kaolinite clay composites were prepared by in situ chemical polymerization of pyrrole in the presence of kaolinite using FeCl₃ as oxidant. The PPy content and conductivity of the composites reached 32.8% and 8.3×10^?2 S/cm at HCl concentrations of 1.5 M and 0.5 M, respectively. The microhardness of the composites containing different amounts of PPy was higher than that of the PPy and kaolinite components. The highest microhardness observed was 30.17 kg/mm² for the composite containing 9.6% PPy. The electrical resistance of the composites was monitored during heating–cooling cycles over the range 5–120 °C. The change in resistance with temperature was more repeatable for the composite than for PPy. The composites were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The humidity-sensing properties were also examined.     

一种雷达阵面T/R供电模块的研究与实践

雷达阵面大规模发射/接收组件高可靠性和安全性工作,给其供电系统提出了越来越高的要求。新一代有源相控阵雷达常采用两级式供电网络,实现应力分散。该文研究了适合于阵面二次电源应用的倍流整流式半桥变换器系统,建立了系统的小信号模型,在频域内设计了系统的补偿环节参数,样机试验结果表明了分析与设计的正确性,也验证了倍流整流式半桥变换器作为二次电源应用于两级式供电网络方案的可行性。     

Piezojunction effect of a planar n-p-n transistor for transducer aims

Measurements of the piezojunction effect of planar n-p-n transistors are reported. The principle for a pressure transducer that makes use of the variation of the base-emitter voltage as a function of the pressure is described. The transducer uses a balanced configuration to lower the temperature sensitivity. Together with the transducer transistors, an adjustment circuit and an output amplifier are integrated on the same chip. Measurements of the complete transducer show a sensitivity of 2 mV per gram exercised force.     

Design and noise analysis of a sigma-delta capacitive micromachined accelerometer

A single-loop fourth-order sigma-delta (∑△) interface circuit for a closed-loop micromachined accelerometer is presented.Two additional electronic integrators are cascaded with the micromachined sensing element to form a fourth-order loop filter.The three main noise sources affecting the overall system resolution of a ∑Δ accelerometer,mechanical noise,electronic noise and quantization noise,are analyzed in detail.Accurate mathematical formulas for electronic and quantization noise are established.The ASIC is fabricated in a 0.5 μm two-metal two-poly n-well CMOS process.The test results indicate that the mechanical noise and electronic noise are 1 μg(Hz) and 8 μV/(Hz)respectively,and the theoretical models of electronic and quantization noise agree well with the test and simulation results.     

Design and noise analysis of a sigma-delta capacitive micromachined accelerometer

A single-loop fourth-order sigma-delta(ΣΔ) interface circuit for a closed-loop micromachined accelerometer is presented.Two additional electronic integrators are cascaded with the micromachined sensing element to form a fourth-order loop filter.The three main noise sources affecting the overall system resolution of aΣΔaccelerometer, mechanical noise,electronic noise and quantization noise,are analyzed in detail.Accurate mathematical formulas for electronic and quantization noise are established.The ASIC ...     

On the accuracy of direct extraction of the heterojunction-bipolar-transistor equivalent-circuit model parameters C/sub /spl pi//, C/sub BC/, and R/sub E/

Several basic small-signal equivalent-circuit models for bipolar transistors lead to simple analytical expressions for the model parameters in terms of measured values. This paper investigates the accuracy of these expressions for real transistors by applying the direct extraction equations to more complicated small-signal models. The extraction of the base/collector capacitance, base/emitter capacitance, and emitter resistance are considered. Analytically derived trends are illustrated using measurements on small-area high-speed InP/GaAsSb/InP double heterojunction bipolar transistors.     

A low-noise low-offset capacitive sensing amplifier for a 50-/spl mu/g//spl radic/Hz monolithic CMOS MEMS accelerometer

This paper describes a CMOS capacitive sensing amplifier for a monolithic MEMS accelerometer fabricated by post-CMOS surface micromachining. This chopper stabilized amplifier employs capacitance matching with optimal transistor sizing to minimize sensor noise floor. Offsets due to sensor and circuit are reduced by ac offset calibration and dc offset cancellation based on a differential difference amplifier (DDA). Low-duty-cycle periodic reset is used to establish robust dc bias at the sensing electrodes with low noise. This work shows that continuous-time voltage sensing can achieve lower noise than switched-capacitor charge integration for sensing ultra-small capacitance changes. A prototype accelerometer integrated with this circuit achieves 50-/spl mu/g//spl radic/Hz acceleration noise floor and 0.02-aF//spl radic/Hz capacitance noise floor while chopped at 1 MHz.     

Non-ideal behavior of a driving resonator loop in a vibratory capacitive microgyroscope

Many researches have been carried out on the dynamic characteristics of vibratory microgyroscope, but only a few have been carried out on the non-ideal behaviors observed in the driving loop of the vibratory microgyroscope. In this paper, characterization and evaluation of the non-ideal behavior of the vibratory microgyroscope, “peak-and-valley” magnitude phenomenon and phase lag distortion, are discussed. To characterize the non-ideal behavior of a microgyroscope driving loop, a new electro-mechanical simulation model based on the HSPICE of microgyroscope driving loop is proposed. The parasitic capacitive components of the driving loop are found to be the major sources of non-ideal behavior in microgyroscope and it is verified with the simulation results. The validity of the proposed simulation model and the parasitic effects on microgyroscope driving loop is evaluated with the actual fabricated gyroscope.