基于目标模拟器的测量雷达相位一致性测试方法

相位一致性直接影响测量雷达的测角精度,因此在重大任务前必须对一致性进行测试,而常用测试方法如注入法安装架设复杂、使用条件要求高,标定法又过度依赖于标校塔或标校架,在地形受限时无法使用。该文中提出一种利用雷达自带的目标模拟器进行"注入式"相位一致性测试的方法,可对除馈源和天线以外的部分进行相位一致性测试,并在某型精密跟踪测量雷达上进行验证。结果表明:该方法操作简便,精度与常规注入法相当,可应用于基层雷达站进行相位一致性自检及野外临时阵地等不具备常规测试方法的场合。     

红外目标旋转模拟器校准方法的研究设想

文章简要介绍了红外目标旋转模拟器的结构组成、工作原理,给出了红外目标旋转模拟器的目标温度、平均角速度、角速度波动的校准方法,该校准方法能为光电设备的量值溯源提供解决方案.     

基于时间延迟的移动目标模拟器的设计与实现

针对实验室环境下单光束脉冲激光测速仪校准问题,本文提出了一种移动目标模拟器的设计与实现方法,该方法基于时间延迟的高精度脉冲序列的产生原理。文中设计了特定的延时脉冲序列,通过软件编程,控制数据定时发生器作为硬件电路生成设备,完成了延时脉冲序列的存储分配和电路生成,实现了具有任意标准速度的通用移动目标模拟器,并构建了激光测速仪检定装置。实验结果表明装置具有较好的测量重复性。     

大面积平行光幕弹着点测试系统

研究了基于平行激光幕大面积弹着点坐标测试方法.以半导体激光线发生器为光源,用长焦距消球差的柱面菲涅耳透镜形成平行激光幕单元,通过多个平行激光幕单元的无缝拼接可形成大面积靶面.由于平行激光幕单元内沿宽度方向通量密度呈高斯分布,一定直径的弹丸通过光幕的不同横向位置时探测器获取信号不同,因此可根据信号的幅值来细分平行激光幕单元宽度范围内弹着点的位置.通过口径为7.62mm的实弹射击试验验证了细分方法的可行性.结果表明了该系统有足够的灵敏度能获取小目标的过靶信号;在10 m长靶面的试验系统中测量坐标值与弹孔测量坐标值差值的标准差为5.16 mm.     

红外目标模拟器中分离镜的滑模变结构控制

针对红外目标模拟器中分离镜伺服系统的抗干扰控制问题,本文利用变结构控制响应快速,对系统参数变化和外部扰动不灵敏的特点设计了一个滑模变结构控制器.采用指数趋近律与饱和函数相结合的方法对滑模控制器的抖振进行了有效抑制.采用机理分析方法建立了分离镜系统的数学模型.在仿真过程中,利用S函数描述摩擦模型,简化了仿真建模,提高了仿真速度.通过数字仿真并与传统PID控制方法相比较,证明滑模控制器对于分离镜伺服系统的参数摄动和外部干扰具有良好的鲁棒性,可以保证和提高整个红外制导仿真实验系统的仿真精度和实验结果的置信度.     

带干扰雷达型目标模拟器校准方法

为解决雷达型目标模拟器中干扰信号参数的校准难题,提出一种基于软件无线电思想的校准方法,通过对目标模拟器输出的回波信号下变频,并进行数字化处理,匹配预设的干扰信号模型,解算出干扰信号参数,实现带干扰雷达型目标模拟器的校准。研建雷达型目标模拟器校准系统,对某型目标模拟器进行校准,并对校准结果进行不确定度评定。校准结果表明:干扰信号参数误差3%以内,拖引速度不确定度1 m/s,拖引加速度不确定度0.2 m/s~2,干扰信号捕获、拖引、保持与关机时间的不确定度为0.01 s,校准结果证明该方法可以应用于带干扰雷达型目标模拟器的校准。     

基于PXI的水下目标辐射噪声和信号模拟器

文中以宽带和多目标信号为模型,在虚拟仪器开发环境LabWindows/CVI下,设计和开发了基于PXI总线的水下目标模拟器。目标模拟器产生24阵元平面水声基阵的接收信号,在实验室里模拟海洋环境下的目标回波、混响和环境噪声,提供测试水声设备所需的各种目标信号。最后给出了该系统在水声自导系统调试和性能测试应用中的结果。     

A novel technique to measure laser beam spot sizes

In this letter we report a novel technique to measure small laser beam spot sizes. We use the open aperture z-scan technique as a tool to measure the laser beam spot size. This technique measures small spot sizes with accuracy better than 10%.     

灰度形态学滤波的红外运动小目标检测方法

针对空中红外图像中运动小目标的特征，提出一种采用灰度形态学滤波的背景抑制方法对图像进行处理，再利用自适应阈值分割方法对图像进行阈值分割的帧内检测方法；实践证明该技术能有效提高图像的信噪比，从而达到有效分割和快速检测小目标的目的。     

Effect of beam divergence from the optic axis in an electro-optic experiment to measure an induced Jones birefringence

Certain optical properties can be described in terms of two linear birefringences existing in separate Jones platelets of a medium. One of these, known as Jones birefringence, although occurring naturally in some crystals is too small to be measurable. However, the two birefringences can be induced by an electric field in 4 and 6 crystals for propagation along the optic axis. For an even slightly divergent light beam, natural birefringence may affect accuracy of measurement. Calculations show that in an experiment with a static field the error depends critically on beam divergence, whereas with a modulated field this is not so.     

A new method to obtain Fourier transform infrared spectra free from water vapor disturbance

Infrared absorption bands due to water vapor in the mid-infrared regions often obscure important spectral features of the sample. Here, we provide a novel method to collect a qualified infrared spectrum without any water vapor interference. The scanning procedure for a single-beam spectrum of the sample is divided into two stages under an atmosphere with fluctuating humidity. In the first stage, the sample spectrum is measured with approximately the same number of scans as the background. If the absorbance of water vapor in the spectrum is positive (or negative) at the end of the first stage, then the relative humidity in the sample compartment of the spectrometer is changed by a dry (or wet) air blow at the start of the second stage while the measurement of the sample spectrum continues. After the relative humidity changes to a lower (or higher) level than that of the previously collected background spectrum, water vapor peaks will become smaller and smaller with the increase in scanning number during the second stage. When the interfering water lines disappear from the spectrum, the acquisition of a sample spectrum is terminated. In this way, water vapor interference can finally be removed completely.     

Generalizing from single target search to multiple target search

This study was conducted to generalize from models of human performance in single target search to multiple target search. The specific issue was exhaustive search for the complete set of targets on a search field, extending the work of Chan and Chan from a two-target exhaustive search. Mathematical modelling was based on earlier derivations of search for the first of a set of targets. Model and simulation results showed three quite different relationships between mean search time and the number of targets remaining in a search field. The human search strategy for multiple targets was close to the systematic strategy for the first few targets and was close to the random strategy for the last few targets. Plotting mean search time for multiple targets against the number of targets remaining would be a useful and unique way to show human use of systematic search strategy.     

An approach to the infrared study of materials by photothermal beam deflection spectroscopy

Infrared Fourier transform photothermal beam deflection spectroscopy (PBDS) is briefly outlined. It involves heating a surface by the photothermal effect, using infrared (IR) radiation from a scanning interferometer; energy is transferred to the gas above the surface and the resulting refractive index gradient in the gas is detected by observing the deflection of a laser beam grazing the solid's surface; the deflection is related to the IR radiation which is absorbed, so that the Fourier transform of the deflection signal results in the IR spectrum. PBDS is especially useful for materials which scatter and/or absorb IR radiation so extensively that conventional transmission/absorption techniques are not possible. A variety of examples of applications are given, including spectra of polymers, floor tile, polyester thread and fabric, leather, cellulose, paper, lichen and bone.     

A thermoelastic method to measure the thermal expansion coefficient

In two different laboratories, measurements are performed of the thermal expansion coefficient of several mortar specimens, based on the thermoelastic effect. The temperature of the sample surface is recorded while the specimens undergo a uniaxial adiabatic compression. The percentage change of temperature is proportional to the longitudinal strain, the constant of proportionality being the longitudinal Grüneisen parameter. Through the equation of state, this parameter allows access to the thermal expansion coefficient once the Young modulus and the specific heat at constant volume are independently available. Results obtained for groups of equally prepared specimens, using two slightly different experemental setups, are found to be identical within the experimental errors. These results based on the thermoelastic method, are also consistent with those independently obtained by direct extensometric methods.

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Résumé On présente une méthode de mesure du coefficient de dilatation thermique des matériaux à base de ciment. La méthode est fondée sur l'équation d'état et se base sur la mesure du coefficient de couplage thermoélastique, le paramètre de Grüneisen. Quand un échantillon est soumis à une charge compressive uniaxiale, en régime élastique et en conditions adiabatiques, sa température augmente par l'effet thermoélastique. La variation relative de température est proportionnelle à la déformation longitudinale, la constante de proportionnalité étant le paramètre de Grüneisen longitudinal. L'équation d'état permet d'obtenir le coefficient de dilatation thermique comme le produit du paramètre de Grüneisen longitudinal, de l'inverse du modulus de Young, et de la capacité thermique par unité de volume, à volume constant. On présente une série de mesures comparées, effectuées dans deux laboratoires sur deux séries d'échantillons de mortier. Les échantillons sont soumis à un essai de compression, pendant lequel on enregistre la charge appliquée et la température de la surface des échantillons mêmes. Le paramètre de Grüneisen longitudinal et le modulus de Young sont déterminés par les caractéristiques température-déformtion et charge-déformation. La capacité thermique par unité de volume est déterminée, dans un essai indépendant, comme le rapport de la diffusivité thermique et de la conductivité thermique, qui font souvent partie d'une qualification adéquate du matériau. Le coefficient de dilatation thermique est enfin déduit comme indiqué auparavant. Les valeurs expérimentales obtenues dans les deux laboratoires diffèrent par moins d'une déviation standard. Les valeurs dites sont comparées avec celles obtenues par une méthode extensométrique, indépendante et plus directe. Les résultats des deux méthodes se révèlent concordants. On conclut que la méthode proposée, basée sur l'effet thermoélastique, bien qu'indirecte, conduit à une mesure fine et précise du coefficient de dilatation thermique.