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.     

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.     

小波变换在雷达目标识别中的应用

针对传统傅里叶变换对雷达回波信号分析方法所存在的不足,提出了利用小波变换的方法来改善雷达回波信号的质量.分析了小波变换的原理,并在此基础上着重论述了小波变换去除噪声的原理和方法.仿真试验和实际数据验证结果表明,该方法改善了雷达回波信号中波形的质量,提高了目标信号的识别率,切实可行,具有一定应用价值.     

Integrated Application of Borehole Radar Reflection and Resistivity Tomography to Delineate Fractures at a Granite Quarry

To delineate the inhomogeneities including fractures and to estimate the freshness of rock, borehole radar and resistivity tomography surveys were conducted at a granite quarry mine in Korea. Borehole radar reflection images were obtained at five boreholes and we could get high resolution image of fractures. Spatial orientations of fractures, however, could not be attained because of omni-directional characteristic of antennas. Radar tomography method, a very useful method to estimate the freshness of rock, was also applied but we failed to get images of fractures because vertical fractures were dominant in this site. To get tomographic image of vertical fractures, we conducted the resistivity tomography over eight sections. Although resistivity tomography method provides very low resolution image of the subsurface compared to radar method, we could get tomographic images of vertical fractures. Spatial orientations of fractures were easily obtained by joint interpretation of radar reflection and resistivity tomography images, and we could accurately define the fractures in 3-D manner. Moreover, we could estimate the physical property of fractures by resistivity tomograms, which have been used to successfully explain the hydrogeologic setting of granite quarry mine.     

大气边界层探测技术初步分析

大气边界层的探测方法呈现多样化趋势,本文重点介绍了几种常用的边界层探测方法,并进行了初步的分析,指出了探测方法的一些缺点和不足。最后,本文就大气边界层探测发展方向做了一些探讨。     

脉冲调频法测距在机载PD雷达中的应用研究

文中对机载脉冲多普勒雷达在HPRF（高脉冲重复频率）状态下,使用PRF转换法和线性调频测距的优缺点进行了比较分析,提出了采用二者综合运用的测距方法。结果表明,该方法能够在HPR．F工作模式下完成远距离目标速度测量的同时,获得精度较高的距离测量值。     

综合利用各类信息的红外/雷达数据关联

异类传感器数据关联是数据融合中的一个难点,综合利用角度和其他特征信息是改善异类传感器数据关联的一个重要途径.对于雷达在直角坐标系对目标进行跟踪、红外传感器在修正的球坐标系对目标进行跟踪情况,文中综合利用角度、角度变化率和ITG(Inverse-Time-to-Go)信息,构建了新的关联统计量,并进行了计算机仿真.结果表明:文中给出的新关联统计量较之只利用角度和ITG信息的关联统计量有更好的关联性能.     

Clutter Reduction and Detection of Minelike Objects in Ground Penetrating Radar Data Using Wavelets

Ground Penetrating Radar (GPR) signatures of shallowly buried landmines are normally obscured by a strong background signal comprised of the reflections from the ground surface and the antenna crosstalk. Based on the notion that buried landmine produces an anomaly in the soil dielectric an automated procedure has been developed which detects soil dieletric anomalies of the size comparable to the size of landmine in GPR data and enhances the signatures of such anomalies. A local background estimate is computed and a soil dielectric anomaly is detected at the spatial position where a change from the estimated background signal occurs. A translation invariant wavelet packet decomposition is applied for detection. The computation takes place in a running window which allows for the algorithm to adapt to the variations in ground conditions and antenna height. The technique was tested using a number of minelike targets buried in several different soil environments and the testing results are presented.     

钻孔水力开采用气力提升装置的实验研究

为阐明进气方式对气力提升特性的作用规律,以普通河沙模拟井下矿层,利用小型输沙系统实验研究在恒定浸入率和供沙量下气孔数量与进气角度对扬水量、扬沙量及总效率的影响。结果表明:任一进气方式下扬水量、扬沙量及总效率并不随气量值增加呈现单调特性,前两者峰值所处位置大致接近,且较总效率峰值对应点右移。气孔数量和进气角度对扬水量及扬沙量影响较小,对总效率影响程度稍大。就整体而言,对应气孔数量和进气角度分别为4和90°时其扬沙量与总效率较其它进气方式上扬。另外,实验测得最高扬沙效率所对气相佛汝德数大致相同,约为2.5,且最佳扬沙效率所对应的气相佛汝德数随管径递增。     

穿层孔施工钻机调角支撑机构的研究

随着瓦斯治理技术的发展,钻掘交替矛盾日益突出,现有钻机虽然能够满足钻孔的需求,但其机动性差,稳钻和固定钻进角度辅助时间长,已不能很好地满足穿层钻孔的施工要求,为此研制一种机动灵活、能够快速支撑稳钻的钻机,文中讨论了该种穿层孔施工钻机用于支撑稳钻的可调角支撑机构。     

稀土改性碳纳米管宽带吸波材料

以碳纳米管为雷达波吸收剂进行稀土掺杂后,和环氧树脂充分混合,制成复合吸波涂料并涂覆在铝板上制成吸波涂层,使用反射率扫频测量系统检测碳纳米管的吸波性能。结果表明：用适量稀土氧化物改性后,碳纳米管的吸波性能大幅提高,在8．40～16．08GHz频段内,反射率R〈-10dg,带宽迭7．68GHz,峰值R=-29．10dB,波峰在10．88GHz。反射率R〈-5dB的带宽达10．60GHz。     

雷达底座机器人焊接的模拟仿真

雷达底座是整个雷达天线系统中的重要部件,使用KUKA Sim Pro仿真软件,对雷达底座进行了机器人焊接的模拟仿真,并与现场实际的焊接过程进行了对比分析,证明了仿真软件的模拟仿真结紧可以用于指导实际产品的机器人焊接。     

机载合成孔径雷达原理及应用

论文阐述了合成孔径雷达与实孔径雷达工作原理的差别,分析了采用线性调频信号提高雷达距离向分辨力和孔径合成提高方位向分辨力技术途径,并对机载合成孔径雷达的应用及发展做了简要介绍和说明.     

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.     

硬质合金滚刀变偏距重磨的数值仿真

以齿侧面加工的铲磨工序为基础,建立了直槽硬质合金滚刀变偏距重磨的数值仿真模型。根据计算机模拟变偏距重磨的数据可知:变偏距重磨比等偏距重磨能较大地改善滚刀重磨后的齿形精度。文中的仿真模型亦可用于零前角及正前角齿轮滚刀重磨后的齿形误差计算和齿形的修正。     

Application of Near-Space Passive Radar for Homeland Security

To protect the homeland from terrorist attacks employing explosive devices, revolutionary advances across a wide range of technologies are required. Inspired by recent advances in near-space (defined as the region between 20 km and 100 km), this paper proposes a new passive radar system using opportunistic transmitter as an illuminator and near-space platform as a receiver. This concept differs substantially from current radars. This system can be operated as a passive bistatic or multistatic radar and hence largely immune to jamming. By placing the receiver in near-space platforms, many functions that are currently performed with satellites or airplanes could be performed much more cheaply and with much greater operational utility. These advantages make near-space passive attractive for a variety of applications, many of which fit well with the needs of homeland security. This paper details the role of near-space passive radar as sensor system that can support homeland security applications. The strengths and weakness of near-space passive radar, compared to current spaceborne and airborne radars, are detailed. The signal models and processing algorithms for near-space passive radar are provided. It is shown that the use of cost effective near-space platforms can provide the solutions that were previously thought to be out of reach to remote sensing and government customers.     

机载雷达系统测试性分析

为了提高系统测试性设计在系统故障诊断和故障隔离中的效能,提出了基于FMEA分析的测试性建模方法.根据机载PD雷达的组成和主要功能,结合FMEA分析结果,建立了机载PD雷达系统的测试性模型,对模型的测试性参数进行了计算和分析.针对提高故障隔离率、降低更换费用等不同要求,设计了系统模型的改进方案,分析结果表明,对模型的改进达到了预期的目的.     

受限MUSIC法在雷达中的应用

分析了用“受限MUSIC法”对多目标的检测,对它应用于高频地波雷达的情况,进行了建模和仿真,仿真结果表明,受限“MUSIC算法”可以有效将相干的信号与海杂波分辨开来。     

Technical Analyses of the Interference Effect of “Advanced Radar”

The conception ofadvanced radaris introduced and put forward,while it is proved that the weakpoints of interference can still be employed.Meanwhile,the paper expands the principle how Over-The-Horizon Radar(OTHR)works,and derives the OTHR interference equation.By listing the OTHR examples,it analyzes and calculates the equivalent power of the OTHR and the sensitivity of the receiver to build up a block diagram how the interferencer is structured Hence,the effective area is achieved,and OTHR can be intereferenced effectively with not so high equivalent power.