低频探地雷达接收机研制

发布时间：2019-04-27 11:35

【摘要】：探地雷达（Ground Penertrating Radar，GPR）作为一种地球物理方法，广泛应用于不同领域的地下目标无损探测。由于地下介质电磁特性的复杂程度以及目标的反射特性各不相同，为了获得良好的探测准确性，探地雷达一般都是专机专用。为了实现青海冻土地区可燃冰的探测，要求探地雷达在该地区具有130米以上的探测深度。目前的探地雷达大多应用于几厘米到50米的探测深度，，天线中心频率集中在10MHz到4GHz范围内。为了实现预期的探测深度，在增强发射雷达波在地下介质中的穿透能力的同时提高对回波信号的补偿能力。本文主要对探地雷达系统的接收机部分进行设计，全文主要工作如下：系统分析与整体设计。先对探地雷达系统的探测原理和接收机的设计需求进行研究分析，通过对不同雷达体制优缺点的说明和对比，选择了野外探测中移动方便显示直观的冲激脉冲体制雷达。在明确发射信号形式及信号衰减影响因素后，结合理论分析与经验公式制定出设计指标，并给出了接收机硬件总体设计方案，即具有时变增益功能的内同步实时采样探地雷达接收机。接收机设计实现分为硬件电路、FPGA控制逻辑和上位机软件设计三个部分。硬件电路部分，根据功能设计要求，同时考虑接收机各性能指标，分别对采样触发电路、时变增益放大电路、ADC采样电路和数据传输电路进行详细的设计说明。FPGA控制逻辑部分，对应各部分电路功能，分4个模块进行基于ISE的FPGA逻辑设计。接收机与上位机采用USB总线进行数据传输，上位机软件使用LabVIEW编写，能够完成对AD采样数据的接收、数据显示、波形显示及数据存储工作，还可以实现对增益的阶梯式连续设定。接收机功能及性能测试工作。完成了对时变增益放大、数据采集、数据传输功能的测试验证；另外，还对噪声系数、灵敏度、带宽及动态范围这些接收机性能评价参数进行测试，测试结果表明设计满足功能要求，性能优秀。相比于传统的冲激脉冲探地雷达接收机，本文的设计具有信号能量利用率高的优点，接收机的动态范围得到有效的扩大，同时所采用的内同步方式能够避免外同步方式中同步电缆移动造成的干扰。
[Abstract]:As a geophysical method, ground penetrating radar (Ground Penertrating Radar,GPR) is widely used in nondestructive detection of underground targets in different fields. Due to the complexity of electromagnetic characteristics of underground media and the reflection characteristics of targets, ground penetrating radar (GPR) is usually dedicated to special aircraft in order to obtain good detection accuracy. In order to realize the detection of flammable ice in permafrost area of Qinghai Province, the ground penetrating radar (GPR) is required to have a depth of more than 130 meters in this area. At present, ground penetrating radar (GPR) is mostly used in detection depths ranging from a few centimeters to 50 meters, and the central frequency of the antenna is concentrated in the range of 10MHz to 4GHz. In order to achieve the expected detection depth, the transmitting radar wave penetration ability in the underground medium is enhanced, and the compensation ability to the echo signal is improved at the same time. This paper mainly designs the receiver part of the ground penetrating radar system. The main work of this paper is as follows: system analysis and overall design. Firstly, the detection principle of ground penetrating radar system and the design requirement of receiver are studied and analyzed. Through the explanation and comparison of the advantages and disadvantages of different radar systems, the impulse pulse radar which is convenient to display in the field detection is selected. After defining the form of the transmitted signal and the influence factors of the signal attenuation, the design index is drawn up according to the theoretical analysis and empirical formula, and the overall design scheme of the receiver hardware is given. An internal synchronous real-time sampling ground penetrating radar (GPR) receiver with time-varying gain function is proposed. The receiver design is divided into three parts: hardware circuit, FPGA control logic and upper computer software design. In the part of hardware circuit, according to the requirement of function design and taking into account each performance index of receiver, the sampling trigger circuit and time-varying gain amplifier circuit, respectively, are taken into account. ADC sampling circuit and data transmission circuit are described in detail. FPGA control logic part, corresponding to each part of the circuit function, is divided into four modules to design the FPGA logic based on ISE. The receiver adopts USB bus to transmit the data between the receiver and the upper computer, and the software of the host computer is written with LabVIEW. The receiver can receive, display the data, display the waveform and store the data of the AD. It can also realize the step-by-step continuous setting of gain. Receiver function and performance testing work. The functions of time-varying gain amplification, data acquisition and data transmission are tested and verified. In addition, the performance evaluation parameters such as noise figure, sensitivity, bandwidth and dynamic range are tested. The test results show that the design meets the functional requirements and the performance is excellent. Compared with the traditional impulse ground penetrating radar receiver, the design of this paper has the advantages of high signal energy efficiency, and the dynamic range of the receiver has been effectively expanded. At the same time, the internal synchronization method can avoid the interference caused by the synchronous cable movement in the external synchronization mode.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN957.5

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