Polarimetric Borehole Radar System for Fracture Measurement

Radar polarimetry is a technology that overcomes the limitation between the radar resolution and the penetration depth of borehole radar. We have developed a stepped-frequency polarimetric borehole radar system. This is a polarimetric borehole radar system which measures the full-radar polarimetry in a borehole by changing the antenna arrangements. By using a network analyzer and an optical analog signal link, this system has a frequency bandwidth of 2–500MHz, which is suitable for two different antennas for radar polarimetry. We also propose a technique for polarimetric antenna calibration. In order to understand the potential of polarimetric borehole radar, field measurement were carried out at the Mirror Lake fractured-rock research site (NH, USA). The radar penetration depth from the borehole in the reflection measurement was over 10m, at the frequency range of 2–402MHz. We observed many clear reflections from fractures in each polarization status. Even in the raw data, we found the differences in the radar profile for different polarization status. We believe the polarimetric feature is closely related to the roughness of each fracture, and it is also related to the physical properties of the fracture such as water permeability.     

A Directional Borehole Radar System

In this paper we present the simulation and design of a directional borehole radar. In addition we discuss an imaging method for the radar system. The antenna system contains an electric dipole which is in one direction shielded by a cylindrical perfectly conducting reflector. The radiation pattern of the reflected wavefield is computed by first solving the integral equation. This equation combines the unknown electric surface current density on the reflector and the known incident field from the electric dipole. Once the electric surface current density is known, the radiation pattern of the system is computed using the integral representation over the reflector and the dipole. The radiation patterns for various configurations have been computed in order to find an optimal configuration. A prototype of the antenna system based on an optimal configuration has been built, and the directional radiation pattern has been measured in the plane perpendicular to the antenna system. The measurements were in good agreement with the computations. Subsequently a three dimensional imaging method for the borehole radar is presented. Here a deconvolution is carried out in the angular direction, making use of the computed radiation pattern. Some imaging results will be shown.     

移动式二次雷达结构设计关键技术研究

移动式二次雷达是具有一定的机动性,用于执行各种临时性任务的空管装备.文中研究配置全尺寸天线且满足高架移动要求的移动式二次雷达,以解决之前配置小天线的移动式二次雷达探测精度与威力低的问题.文中通过研究系统总体布局以及小型化、轻型化、智能型天线驱动系统和刚强度优良的升降式高架天线塔等的结构设计关键技术,优化天线风载特性,使...     

Numerical and Field Investigations of GPR: Toward an Airborne GPR

The main objective of our work is to explore the feasibility of designing an airborne RADAR system much like the University of Texas Institute for Geophysics airborne ice-penetrating radar systems for use in the detection of underground structures. Here we summarize our initial efforts toward achieving this goal. The studies conducted so far include two major tasks: (1) development of hybrid numerical-analytical techniques for simulating the radar response of underground targets, and (2) a ground penetrating radar field experiment conducted at a known site that has underground tunnels. In our numerical simulation, we used analytic solutions to propagate the EM wave field from an airplane to the ground surface and then used a finite difference scheme to compute the response of complex geology including some underground structure. During the field investigation, we collected several surface GPR profiles with varying source-receiving antenna separations and configurations. The data were processed using algorithms similar to those used in seismic data processing. Despite the high moisture content in the field area during data collection, we were able to identify features in the data that can be modeled as diffractions from underground targets. The results are encouraging. Our future work will include revisiting the site during the summer months since we expect to be able to image the underground facilities better when the ground is dry. Based on the success of the ground based GPR field surveys, we will investigate the possibilities of designing and testing an airborne system.     

基于挠曲线方程的某车载雷达天线质心估算方法

对于车载雷达转塔系统,准确地确定雷达天线的质心位置对转塔的受力分析、设计校核和实际使用都至关重要。文中提出了一种大型雷达天线质心位置估算方法,根据悬臂梁所受集中力的挠曲线近似微分方程,建立转塔系统的数学模型,将测量数据代入模型,所得结果与理论计算结果相差1.83%。该方法不受限于场地和测量设备,计算过程简单,结果准确,可为相关车载雷达天线或相似结构产品的质心位置估算提供理论指导和工程应用参考。     

Polarimetric Video Impulse Radar for Landmine Detection

A full-polarimetric ultra wideband GPR front-end has been developed. The technical specifications of the radar have been determined based on the analysis of different GPR scenarios and based on user-oriented demands. The radar has been designed to meet most of these specifications and at the same time to be within a limited budget. The front-end comprises a generator section, a multi-static antenna system and a receiving unit based on a multi-channel sampling converter. The novelty aspects of the radar are: principally new antenna system, use of multiple pulse generators and compensation circuits to improve stability of the system. In comparison with commercially available video impulse GPR systems the key advantages of the front-end are the considerably larger bandwidth, the ability to measure the polarimetric structure of the scattered field and the high precision of scattered field measurements. The front-end is suitable for subsurface imaging with 3D resolution sufficient for antipersonnel mine detection and recognition.     

大型雷达天线六自由度自动对接平台设计

米波雷达具有天线口径大、质量重、需分离运输的特点,目前天线的拼装大多采用人工或吊车辅助的方式,耗时长且存在不安全因素。为解决米波雷达天线的快速拼装难题,本文介绍了一种用于大型机动型雷达天线的六自由度自动对接平台,对其工作原理、组合机构、液压系统、控制系统等的设计进行了详细的论述。该平台已用于某型雷达天线,实现了天线的自动对接拼装,提高了雷达的机动性。该平台技术可为其他大型机动雷达提供设计参考。     

大型固定式相控阵雷达阵面安装方式研究

随着洲际弹道导弹、潜射弹道导弹、多弹头分导再入式导弹等进攻性武器和各种卫星的发展,对覆盖距离远、分辨率高、跟踪目标多的多功能探测系统装备——大型相控阵雷达的需求日益增加。近年来,大型相控阵雷达得到了长足的发展,远程预警雷达、远程相控阵雷达、远程防空监测雷达等均已完成阵地布设。不同的天线阵面安装结构形式对雷达装备的架设、阵面精度的控制带来了不同的影响。文中通过对比2部大型固定式相控阵天线阵面安装与阵面精度控制过程,分析了过渡骨架和调整机构2种连接结构形式对天线阵面的安装与精度控制的影响,阐述了两者的优劣之处,对今后大型相控阵雷达的高效、低成本研制和部署具有借鉴意义。     

相控阵雷达天线阵面过线管孔密封研究

相控阵雷达天线阵面上的电缆或水管在穿过阵面箱壁时的过孔处易引发阵面漏水问题,为了解决这一问题,总结了目前已有的可应用于过线管孔处密封的技术,指出采用模块化密封系统是一种密封可靠、安装更换与扩容方便、外形美观的密封方式,并采用了模块化密封系统中焊接与螺接形式的密封件分别制造了试验件,进行了淋雨试验.试验表明,焊接形式的密封件不易发生螺接形式中由于密封垫片选型设计不当导致的漏水问题,且节省安装空间,是一种适于天线阵面上过线管孔处的密封方式.天线阵面在实际设计过程中,可根据密封与成本等要求灵活选用各种密封方式,但在有严格的密封要求、便于安装更换与扩容等情况下,宜优先采用焊接形式的模块化密封系统.     

某相控阵雷达车机动性设计

某相控阵雷达具有集成度高、天线口径大、质量重等特点,其机动性设计是个难题.文中通过对天线阵面进行合理分块并选择合适的折叠方式,设计并使用一套天线自动展/收和调平的自动架设/撤收的液压系统,运用MSC·ADAMS运动分析软件对天线展/收机构进行仿真分析和优化设计,使该雷达车的机动性达到了指标要求,并已通过整机工程实施对其进行了验证.该系统可靠性高,性能优越,对类似雷达车的机动性设计具有一定的参考意义.     

某无源高架雷达结构总体设计要点分析

阐述了某无源高架雷达在结构总体设计过程中的一些设计要点及其实现方法.作为一部高架雷达,天线被可靠地举升到所需高度并稳定工作是结构设计的一个重要方面,因此针对天线系统的减重设计和散热设计、升降杆的安全可靠性设计和气候环境适应性设计等作了介绍,通过完善进一步提高了雷达的安全性、使用性和维修性,供同类产品设计时参考.     

一种CINRAD/SA雷达天线运行监控系统的设计

文章介绍了CINRAD/SA雷达伺服系统的系统构成,并利用RDASC系统软件出现报警而导致伺服系统方位电机或俯仰电机停止供电的原理,巧妙地设计一种CINRAD/SA雷达天线的运行监控电路,以监控雷达天线运行是否正常。文章介绍了系统的总体设计及其基本工作原理。     

场监雷达天线座关键技术研究

场监雷达必须能够快速、实时监视机场内的目标,其数据率通常≤1 s.为实现该指标,天线必须能够实现高速水平旋转(转速通常为60 r/min),而以往的空管雷达天线座均不能满足其指标要求(转速通常为6~15 r/min).文中采用双电机与蜗轮蜗杆式减速机直连驱动设计、高速旋转天线的动平衡设计、高速旋转传动系统的浸油润滑与非接触式旋转密封设计等关键技术以及远程监测天线座内油位和油温、远程监测天线座水平状态、远程进行温控等辅助设计,完成了一种具有可高速水平旋转、可远程监测运行状态、可靠性高的场监雷达天线座研制工作.该研制成果已应用于机场场面监视雷达且无故障运行时间大于17520 h.     

一种抛物面天线的自动折叠方案及实现

介绍了一种全新的抛物面天线自动展开/撤收方案.将天线分成三部分,各部分之间由机构相连,通过机构运动,将天线折叠至运输状态或展开至工作状态,全部机构动作均由液压驱动完成.该方案可大幅度提高中大口径车载抛物面天线雷达的机动性,使该类型的雷达实现高机动成为可能.     

某车载天线工作状态下的结构刚强度分析

车载雷达具有良好的机动能力,能够快速完成转场运输,在任务现场无需借助外部设备即可自主完成系统安装架设与撤收工作,具有很好的应用前景。天线是车载雷达的重要组成部分,其反射面的精度对雷达系统的整体性能有着重要的影响,而反射面的精度是依靠天线自身的结构刚强度保证的,因此对天线刚度和强度的分析和研究非常必要。文中以车载偏馈抛物面天线为例,从实际的技术指标出发,运用有限元分析软件,通过同时加载风力、自身重力和转动惯性力等多种载荷,分析并验证了天线结构设计的可靠性,为以后的设计和优化提供了重要依据。     

大口径星载雷达天线结构分析

论述了大口径星载雷达天线的结构设计,详细介绍了高模量碳纤维框架的设计和平面度、刚度保证措施,对天线的平面度和动态特性分别进行了分析和测试,框架模态的仿真分析结果与实测结果基本一致,为天线发射状态压紧点的优化提供了依据.并用Test Lab中的模态预测软件计算质量增加后结构的模态参数,仿真分析了框架在压紧状态和展开状态的模态.分析表明大口径雷达天线能满足星载结构方面的指标要求,为大口径天线的星载雷达立项打下了基础.     

某雷达平面阵列天线风冷研究

风冷具有设备简单、成本低、可靠性高、安全性好等诸多优点,在现代电子技术飞速发展的今天,仍然是雷达冷却设计时需要优先考虑的方式之一。文中针对某相控阵雷达有源平面阵列天线的冷却需求,利用热仿真软件对其散热结构进行了优化。通过分风单元、静压箱、送风孔板等空气流量分配技术的综合匹配,完成了集中式风源条件下大型平面阵列天线的精确空气流量分配,实现了系统的高集成化风冷设计,拓展了雷达风冷的技术路径,可为类似系统设计提供参考。     

热仿真分析技术在相控阵雷达天线散热设计中的应用

天线阵面散热设计是雷达结构设计中的重要内容,它对提高天线系统的可靠性,保证雷达系统的正常可靠工作等具有重要的意义.同时,随着科学技术的不断进步和发展,热仿真分析技术在现代电子设备热设计中的地位和作用也越来越大.文中以某大型相控阵雷达天线热设计为例,首先对其散热方案进行分析比较,针对所选定的散热方案,应用CFD仿真软件FLUENT对阵面散热进行仿真分析,为天线系统的散热设计提供设计依据和参考,然后对仿真分析的结果进行分析总结,并对热仿真分析技术在复杂系统中的实际应用提出了观点和看法.     

某雷达天线的结构设计与振动条件分解

雷达天线结构设计中,天线中的模块均根据整机振动条件进行设计,造成模块振动条件与真实工作状态的振动条件差别较大,甚至出现单独试验时正常的模块在随天线一起试验时发生损毁的现象.文中论述了某机载雷达天线的结构设计方案,在结构设计中将天线振动条件进行分解,得到天线中各模块的振动响应条件,为各模块的结构设计提供设计依据.同时将天线结构与功能一体化设计,实现天线轻型化设计的同时增加了天线负载的刚度贡献.最后,通过力学仿真和热仿真验证了该设计方案的可行性并通过了试验验证.     

有源相控阵雷达除湿模块技术研究

随着现代相控阵雷达的不断发展,天线阵面的结构密度越来越大,导致了各个功能部件的安装空间逐渐缩小、阵面内部空气流动阻力逐渐变大、对系统中各部件的互联性要求越来越高.传统的仅考虑除湿和防霉功能,将除湿模块作为一个独立模块进行设计的思路已不能适应当前雷达的发展.文中提出了一种将除湿模块与天线阵列进行结构功能一体化设计的思路,该方法可有效解决狭小空间的安装、阵面互联性等问题.最后对设计结果进行了仿真分析,验证了该方法的可行性,设计思路和方法可供同类产品参考和借鉴.