基于中频模板信号的脉冲压缩性能分析

由雷达发射、接收系统导致的信号幅度、相位失真以及由目标径向速度导致的目标多普勒频率是影响脉冲压缩性能的三个主要因素。本文从理论上分析了这三个因素影响脉冲压缩性能的算法原理,通过仿真验证了它们的实际影响效果,对仿真中的情况进行解释说明,对相应指标要求进行了分析,并对在影响脉冲压缩性能的因素存在下的信号处理方法提出了实际的建议。     

Full Complex Amplitude Digital Holograms： Design, Fabrication and Optical Characterization

Diffractive optical elements have a large number of industrial applications, such as beam shaping and optical filtering. Traditionally, these elements modulate the phase of the incoming light or its amplitude, but not both. To overcome this limitation, full complex-amplitude modulation diffractive optical elements were developed. Well-established integrated circuit fabrication steps were employed to fabricate the devices with high precision. Using this approach, the new element‘s optical performances are improved also for near field operations. With this device it is possible to obtain 100% efficient spatial filtering and low noise reconstructed images.     

Propagation of local excitations through strongly correlated quantum chains

The propagation of an external transverse magnetic signal acting locally on a 1d chain of spins generates a disturbance which runs through the system. This quantum effect can be interpreted as a classical travelling wave which contains a superposition of a large set of frequencies depending on the size of the chain. Its local amplitude fixes the size of the z-component of the spins at any location in the chain. The average and maximum value of the group velocity are determined and compared with the transmission velocity fixed by the Lieb-Robinson upper bound inequality.     

基于线偏振光反射率测量介质折射率的研究

研究线偏振光的振幅反射率与介质折射率的关系,提出一种测量介质材料折射率的方法。文中从菲涅耳公式出发,推导出各向同性介质的线偏振光反射率与折射率的关系式,给出基于线偏振光反射率测定介质折射率的原理。设计实验方案,在不同入射角情况,定出线偏振光p方向和s方向两种线偏振光在玻璃表面的反射率,得到线偏振光振幅反射率随入射角变化的实验曲线。依此实验数据得出材料的折射率。结果表明,测出的介质材料的折射率与理论值相符,所采取的测定方案可行。     

基于正弦光栅调制的相位恢复

提出一种基于正弦光栅调制的相位恢复方法.首先,在空间光调制器上加载两个不同方向的正弦光栅对光场复振幅进行调制;然后,推导强度信息和相位偏导数之间的关系式;最后由强度信息计算相位偏导数,进而恢复相位.实验分别测试了该方法对简单图像、复杂图像以及含噪声图像的恢复能力.实验结果表明,该方法可以通过方便地控制图像移动量来有效恢复相位信息,适用于不同尺度的相位物体的计算.     

A study of time over threshold (TOT) technique for plastic scintillator counter

A new charge measurement method, time over threshold (TOT), has been used in some gas detectors lately. Here TOT is studied for TOF system, made of plastic scintillator counter, which can simplify the electronics of the system. The signal characteristics are measured and analyzed with a high quality oscilloscope, including noise, pedestal, signal amplitude, total charge, rise time and the correlation between them. The TOT and charge are related and can be fitted by some empirical formula. The charge measurement resolution by TOT is given and this will help the design of TOF electronics.     

基于单片机的直接数字频率合成器的设计

直接数字频率合成具有一系列优点,如频率切换速度快、频率分辨力高、频率和相位易于控制等。DDFS可以产生各种所需要的波形。根据直接数字频率合成的原理,利用80C51单片机、数/模转换器DAC0832以及一些外围电路设计了一种正弦波发生器。该系统电路设计简单、频率控制灵活,具有良好的实用性和可扩展性,不仅可用于正弦波的发生,还可根据存储器中存放的不同波形数据,输出其他波形。     

中波数字调幅广播发射机的常见故障及维护方法

在现代广播技术系统之中,数字调幅中波广播发射机技术设备是不可或缺的技术设备类型,其.在改善提升广播节目播出质量和播出效率方面作用显著,在支持现代广播媒体事业优质稳定运作发展方面作出了不可替代的历史贡献。围绕中波数字调幅广播发射机的常见故障及维护方法,展开简要的阐释分析。     

射频芯片内DCXO的晶体振荡主电路设计

描述了一种射频芯片内数控晶体振荡器(DCXO)的振荡主电路设计,以Deep-N-Well CMOS工艺的PMOS为主工作管,采用Santos(改进Colpitts)结构、非对称差分式振幅控制环,避免了因Vt依赖工艺与温度等而产生的可靠启振问题.该10MHz DCXO振荡器主电路,采用TSMC Mixed/RF 0.18μm CMOS工艺,在2V电源电压下,仿真得到输出特性为:振幅峰峰值0.8V,平均电流2.9mA,相位噪声-140dBc/Hz@1kHz,-173dBc/Hz@1MHz,启动时间约2.8毫秒,可作为DCXO核心振荡模块.     

基于时间抖动的幅度量化DRFM谐波衰减技术

数字射频存储器（DRFM-Digital Radio Frequency Memory）的优势是可以对现代采用复杂波形的雷达实施干扰，增强了电子对抗设备的干扰能力。但由于需要用A／D变换器将模拟信号变换为数字信号，不可避免地会引入不期望的谐波分量，这些谐波混叠进接收机系统，会降低干扰设备的功率利用率，而且会被受干扰雷达或附加的系统探测到作为识别存在DRFM干扰信号的依据，对干扰源进行攻击。文章主要讨论时间抖动在幅度量化DRFM谐波衰减方面的应用。