射频激励CO_2激光器的阻抗匹配及调制的实验研究

论述了射频（ＲＦ）激励气体放电所必须的在ＲＦ源与激光头放电气体之间的阻抗匹配器的工作原理及其实验，并依据研制成功的千瓦级ＲＦ激励快轴流ＣＯ２激光器的实际参数，论证了气体放电阻抗的计算、动态阻抗调配及ＲＦ泵浦调制的激光实验。     

多功能键盘设计

文中讨论的是多功能键盘，它是以ＡＴ８９Ｃ２０５１单片机为控制器，带有本地键盘和远程无线遥控键盘，适用于特殊场合的一种微机系统智能键盘。文中较详细地介绍了多功能键盘的设计思想、工作原理及软件控制过程等。     

稀布阵综合脉冲孔径雷达目标距离的精密测量和跟踪

本文针对稀布阵综合脉冲孔径雷达(SIAR)提出了两种精密测距方法(分别称为正负频率脉冲综合法和前后脉冲综合法),它们不需要提高采样频率就可以得到较高的测距精度;讨论了时空三维匹配滤波时角度误差对测距的耦合影响;介绍了其跟踪处理过程;并通过计算机仿真证明了这两种方法的有效性。     

短波软件无线电

在近年提出的软件无线电技术的基础，结合短波通信的特点，讨论了一种短波软件无线电的实现。实现的基础是数字信号处理器的可重置性和带限信号的采样原理。系统主要由高速Ａ／Ｄ＆Ｄ／Ａ，可编程ＤＳＰ模块以及多媒体ＰＣ构成，它具有完全的可编程性，而且调试和升级非常便捷。     

频谱分析仪在射电法测量天线增益和G／T值中的应用

本文给出了频谱分析仪在射电法测量天线增益和Ｇ／Ｔ值中的应用方法以及计算公式，并对测量误差进行了分析，讨论了ＬＮＡ的噪声温度与Ｙ因子大小的关系，给出了对测量精度的影响和常用不同频段可测天线口径的下限。     

脉宽可控的腔倒空射频波导CO2激光器

为了得到脉宽可控的腔倒空射频波导CO2激光器,采用了在陶瓷板上直接开波导槽的方法,构成了多通道Z折叠主本振激光器结构,并在主振波导进行CdTe电光晶体腔内调Q。在理论上计算了加载在CdTe上的高压脉冲下降时间的长短对腔倒空激光脉冲宽度的影响,并通过对高压脉冲电源等效负载参数的调整,得到了脉冲宽度可控的高重频腔倒空激光脉冲。在20kHz,40kHz,65kHz及70kHz的重频工作下,得到了半峰全宽约30ns、峰值功率在2kW以上的腔倒空激光脉冲。结果表明,这种新型腔倒空射频波导CO2激光器满足激光外差成像雷达系统参数要求。     

一种新的图像去噪混合滤波方法

为了去除图像中混入的脉冲噪声和高斯噪声,提出了一种基于自适应中值滤波和模糊加权均值滤波的混合滤波方法.该方法首先进行噪声检测把受高斯型噪声污染的像素和受脉冲型噪声污染的像素区别开来,然后对受高斯噪声污染的像素采用模糊加权均值滤波算法,而对受脉冲噪声污染的像素则采用改进的中值滤波算法进行去噪.仿真结果证明,该方法更具有实用性和有效性.     

Performance analysis of a variable‐gain amplify‐and‐forward relayed mixed RF‐FSO system

In this work, an amplify‐and‐forward variable‐gain relayed mixed RF‐FSO system is studied. The considered dual‐hop system consists of a radio frequency (RF) link followed by a free space optical (FSO) channel. The RF link is affected by short‐term multipath fading and long‐term shadowing effects and is assumed to follow the generalized‐K fading distribution that approximates accurately several important distributions often used to model communication channels. The FSO channel experiences fading caused by atmospheric turbulence that is modeled by the gamma‐gamma distribution characterizing moderate and strong turbulence conditions. The FSO channel also suffers path loss and pointing error induced misalignment fading. The performance of the considered system is analyzed under the collective influence of distribution shaping parameters, pointing errors that result in misalignment fading, atmospheric turbulence, and path loss. The moment‐generating function of the Signal power to noise power ratio measured end‐to‐end for this system is derived. The cumulative distribution function for the Signal power to noise power ratio present between the source and destination receiver is also evaluated. Further, we investigate the error and outage performance and the average channel capacity for this system. The analytical expressions in closed form for the outage probability, symbol and bit error rate considering different modulation schemes and channel capacity are also derived. The mathematical expressions obtained are also demonstrated by numerical plots.     

End‐to‐end security‐reliability analysis of multi‐hop cognitive relaying protocol with TAS/SC‐based primary communication,total interference constraint and asymmetric fading channels

In this paper, we analyze the tradeoff between outage probability (OP) and intercept probability (IP) for a multi‐hop relaying scheme in cognitive radio (CR) networks. In the proposed protocol, a multi‐antenna primary transmitter (PT) communicates with a multi‐antenna primary receiver (PR), using transmit antenna selection (TAS) / selection combining (SC) technique, while a secondary source attempts to transmit its data to a secondary destination via a multi‐hop approach in presence of a secondary eavesdropper. The secondary transmitters such as source and relays have to adjust their transmit power to satisfy total interference constraint given by PR. We consider an asymmetric fading channel model, where the secondary channels are Rician fading, while the remaining ones experience the Rayleigh fading. Moreover, an optimal interference allocation method is proposed to minimize OP of the primary network. For the secondary network, we derive exact expressions of end‐to‐end OP and IP which are verified by Monte Carlo simulations.     

大功率射频板条CO_2激光器电极波导介质膜研究

针对高功率射频板条CO2激光器铜电极表面放电氧化、受射频放电的电子溅射,致使电极表面不光滑,辉光放电不均匀,光波导损耗严重等问题。利用Al2O3波导介质膜具有的反常色散效应、耐高温能力强的特点,采用磁控溅射镀膜技术对激光器电极表面先镀Al,而后阳极氧化获得Al2O3波导介质膜。分析了磁控溅射工艺对膜层结构的影响,测量了镀膜电极对CO2激光的反射率,并进行了放电实验检测。结果表明,溅射功率为250 W时可得到致密的镀膜层结构;厚度6μm的Al2O3薄膜,对波长10.6μm的CO2激光波导反射率最高达75%;电极镀膜后激光器输出功率在占空比为30%时为700 W,占空比为60%时达到了1300 W。