DDS在相控雷达系统中的应用

直接数字合成技术（Ｄｉｒｅｃｔ Ｄｉｇｉｔａｌ Ｓｙｎｔｈｅｓｉｓ,缩写ＤＤＳ）是近年来迅速发展起来的一种新型的信号合成技术。由于采用了全数字结构,它具有宽的相对频带、精确的频率分辨率、极快的频率转换速度、低相位噪声及易集成等突出优点．本文提出了将ＤＤＳ应用于相控阵雷达系统,并具体分析了这一应用对整个相控阵雷达系统性能的影响,如复杂雷达基带波形的产生与捷变、低波束跃度实现、低副瓣电平设计等,最后介     

Novel Type of Wide\|Bandwidth GaAs/AlGaAs Infrared Photodetectors

A novel asymmetrical GaAs/AlGaAs photoconductance infrared detector based on the new idea proposed in this paper has been developed,which uses the intersubband transition within the same conduction (valence) band due to infrared radiation.The detectors with two wells or six wells grown by Metalorganic Chemical Vapor Deposition (MOCVD) system are fabricated by etching a mesa size of 200μm×200μm.Evident infrared absorption on the wavelength from 5 to 10μm has been observed for two samples,so has the peak of negative differential conductance.It is demonstrated that the photocurrent together with the signal\|to\|noise ratio increases with the number of the wells,but have nothing to do with the increase of the noise current under the same electric field,i.e.,the voltage drops per period,as is different from the conventional GaAs/AlGaAs Quantum Well Infrared Photodetectors (QWIPs).The noise current is one order's magnitude lower than that of the conventional GaAs/AlGaAs QWIPs.It is anticipated that the photocurrent and detector performances can be improved further by increasing the number of wells and optimizing the structural parameters.     

High Performance Piezoelectric Microspeakers and Thin Speaker Array System

This paper reports on an improved piezoelectric microspeaker with a high sound pressure level of 90 dB, a total harmonic distortion of less than 15%, and coherence higher than 0.9. The fabricated Pb(Zr,Ti)O₃ (PZT) microspeakers have a thickness of only 1 mm including the speaker frame and an active area of 18 mm×20 mm. To achieve higher sound pressure and lower distortion, the PZT piezoelectric microspeaker has a well‐designed speaker frame and a piezoelectric diaphragm consisting of a tilted PZT membrane and silicone buffer layer. From the simulation and measurement results, we confirmed that the silicon buffer layer can lower the first resonant frequency, which enhances the microspeaker's sound pressure at a low frequency range and can also reduce useless distortion generated by the harmonics. The fabricated PZT piezoelectric microspeakers are implemented on a multichannel speaker array system for personal acoustical space generation. The output sound pressure at a 30 cm distance away from the center of the speaker line array is 15 dB higher than the sound pressure at the neighboring region 30 degrees from the vertical axis.     

An evaluation of the optical fiber beam as a force sensor

The present study reports the use of an intensity based plastic optical fiber (POF) as a force sensor. Different materials for beam, such as spring steel and mild steel, are used to evaluate the performance of the force sensor during macro-bending. The POF is surface bonded to a beam and subjected to force. The system relies on monitoring the light intensity, as the POF is subjected to transversal loading conditions. Experimentally obtained output of POF which could be measured with negligible hysteresis is compared with finite element analysis in the range between 0.0098 N to 19.613 N. The reproducibility of the sensor is observed in the limit of ±1%. The finding of this study highlights the potential use of POF sensors for various force sensing applications.     

蓝牙技术在发酵罐自控系统中的应用

介绍了一种利用蓝牙技术的发酵罐自动控制方法，包括系统结构、子系统硬件设计和软件的设计。     

数字中频技术的研究及其FPGA实现

首先给出了软件无线电收/发信机的基本结构,分析了数字化中频技术在其中的关键作用,给出了一种有效的适合于FPGA实现的数字上/下变频方式,并讨论了高阶Fir滤波器在FPGA中采用分布式算法(Distributed Arithmetic)的实现.     

USB及其设备开发

USB(Universal Serial Bus)的中文名叫“通用串行总线”，USB的分时处理机制在硬件的意义上真正实现了计算机外设的即插即用。采用USB设备的产品正在逐渐增加。USB设备的发展势头正如日中天。本文论述了USB及其设备开发过程。     

摄像头LED阵列的电路连接模式优化研究

针对摄像头补光LED(Light Emitting Diode,LED)阵列的布阵优化及电路连接问题,研究了LED的串联阵列、并联阵列以及混联阵列的电路模型,分析了各自的构成特征及可靠性。理论分析与实验结果表明:先并后串的混联网状式LED阵列具有较高的可靠性,能延长阵列寿命,易于与驱动电源匹配,可广泛应用于摄像头补光。     

最小二乘法计算晶格参数

最小二乘法是求解精确晶格参数的基本方法.讨论了使用和不使用校正函数情形下的科恩最小二乘法,给出了所有晶系的法方程、晶格参数、误差估计的计算公式,以及计算晶格参数、校正函数参数的阻尼最小二乘迭代算法,该方法具有普适性,有大的收敛范围和快的收敛速度.作为应用例子,计算了数个不同晶系晶体的晶格参数,说明最小二乘法是获得高精度晶格参数的计算方法;用阻尼最小二乘法计算了ChuG校正函数的参数,表明该方法是获得校正函数参数的有效方法.     

基于CAN_GSM车辆监控系统设计

针对传统车辆监控系统的不足,提出了一种基于CAN／GSM的部队车辆监控系统。该系统采用CAN总线技术,依托GSM网络,将采集到的车辆信息实时传送到监控中心,并且采用动态参数设置,能够对车辆全面,实时地进行监控,具有很好的灵活性和扩展性。