Epitaxial lift-off GaAs HEMT's

An extensive study of epitaxial lift-off (ELO) Al_0.3Ga _0.7As/GaAs modulation doped heterostructure high electron mobility field-effect transistors (HEMT's) is presented. Effects of ELO on electron transport properties of two-dimensional electron gas at AlGaAs/GaAs interface are investigated. An ELO HEMT with 1.5 μm gate length had a maximum extrinsic transconductance g_m-max=125 mS/mm, a unity current gain cut-off frequency f_t=10.5 GHz, and a maximum frequency of oscillation f_max=12 GHz. Statistical distributions of maximum intrinsic transconductance of ELO HEMT's are presented and compared with their on-wafer counterparts. Stability of the ELO HEMT's has also been evaluated by continuous operation at room temperature under dc bias     

A TECHNIQUE FOR MEASURING THE LINEARITY OF A LINEARLY FREQUENCY-MODULATED SIGNAL

A technique for measuring the linearity of a linearly frequency-modulated continuous wave (LFM-CW) signal is presented. It uses a delay-line and a mixer to sense the slope of the output of a sweep oscillator, so that the original form of frequency function deviated from idealized linear slope is retrieved by means of spectrum analysis. Consequently,the linearity of the LFM signal is determined. The formulation is performed based on the principle that an angle-modulated signal can be approximated by an amplitude-modulated signal if the modulation coefficient is sufficiently small. To examine the validity of the procedure and to study the effect of each parameter on the accuracy of measurement, a number of computer simulations has been made. The results of simulation show that the error of the measurement is less than 2%.     

强力输送带横向断裂预报装置中的皮带图象补偿

本文论述了强力输送带横向断裂预报的重要性及其装置的结构和工作原理。找出了皮带图象模糊的原因，提出了图象补偿方法，并由硬件和软件来实现，达到了实时、直观、准确、快速地全面监视皮带内钢绳芯的状况。     

电磁型微电机定子绕组的研制

本文主要阐述应用微细加工技术研究和开发电磁型微电机定子绕组的制备工艺，重点介绍制备定子绕组所涉及到的各种材料及其用途。采用掩模电镀技术解决了平面工艺难以解决的线圈绕组。本研究结果为双层十七圈三对六组绕组系统。最小线宽为３μｍ，微电机直径为２ｍ，最大工作电流１２０ｍＡ，电阻值在２４－２５Ω之间。输出力矩为１．５μＮＭ，转子转速每分钟可达５００转。     

激光刻字机输出多灰度级TIF图象的方法

本文分析了各种TIF图象文件格式,在此基础上,提出了用颤动法在激光刻字机上输出多灰度TIF图象的方法。     

过共晶Al－Si合金共生区激光表面处理

用２ｋＷ连续ＣＯ２激光对过共晶Ａｌ－１８Ｓｉ合金以不同能量密度和扫描速度进行快速熔凝处理。用扫描电镜、电子微区分析仪分析了微观结构。从计算机对Ａｌ－Ｓｉ合金ｆ－ｎｆ系统的非平衡理论计算所得的共生区及实验结果的分析可见，当能量密度和扫描速度决定的凝固条件处于共生区中部时，过共晶Ａｌ－Ｓｉ合金激光表面处理可以得到共晶间距低于２００ｎｍ的完全共晶结构。     

卤化铜激光器在眼科上的应用

卤化铜激光器在眼科应用上的特点及动物实验和临床治疗的情况分析。     

Locally optimum rank detection of correlated random signals inadditive noise

Nonparametric detection of a zero-mean random signal in additive noise is considered. The locally optimum detector based on signs and ranks of observations is derived, for good weak-signal detection performance under any specified noise probability density function. This detector is shown to have interesting similarities to the locally optimum detector for random signals. It may also be viewed as a generalization of the locally optimum rank detector for known signals. Examples of the test statistic of the detector are given for some specific noise probability density functions. Asymptotic and finite sample-size performance of the locally optimum rank detector is also considered     

应用边界元法计算TEM小室中高次模的截止频率

本文提出了应用边界元法求解TEM小室中高次模截止频率的方法,求出了多个TE和TM模式的截止频率值。对于一对称小室,由于利用了电壁和磁壁,所以仅研究横截面的四分之一部分就可以得到满意的结果,并且很容易判断其模式。文中列出了一些计算结果并与其它方法的数据进行了比较。     

线性复合片补偿器

本文给出一种特殊复合延迟片——复合片补偿器。改变入射线偏振光的振动方位角,便可改变补偿器的延迟量,调整简单,精度高。