超高频河流表面动力学参数雷达设计与实验

发布时间：2018-01-13 08:00

本文关键词：超高频河流表面动力学参数雷达设计与实验　出处：《武汉大学》2014年博士论文　论文类型：学位论文

【摘要】：全面认识和充分利用淡水资源,能够为我国的国家安全和经济建设提供有力的保障。传统的水文仪器采用接触式测量,安装和维护不便；而微波遥感技术容易受到降雨、云雾等恶劣天气的影响。因此本文提出利用非接触式超高频河流表面动力学参数雷达(URSDR:UHF River Surface Dynamics parameters Radar)来弥补上述不足。超高频雷达利用水流对雷达电波的布拉格散射形成的多普勒频移来探测河流表面流径向速度。URSDR系统采用线性调频连续波的工作体制,利用回波信号的频率和相位信息来提取动力学参数。URSDR系统的工作频率为340MHz,带宽为15.36MHz,并且帧周期为0.1032s,一个相干积累时间内包含512帧。基于上述参数,URSDR的距离分辨率为9.77m,速度分辨率达0.0084m/s。 URSDR系统由天线、发射机、接收机、计算机、线性电源组成。URSDR接收机是全数字雷达接收机,通过数字端的FPGA产生本振和回波信号混频,将射频载频直接搬移至零频。和传统的超外差雷达接收机相比,省去了模拟端的混频器,因此简化了系统结构,增加了动态范围。URSDR发射机将线性调频信号放大到所需的功率；天线采用“一发六收”的方法,发射和接收天线均为可替换的八木天线；计算机用于初始参数配置、数据存储等；线性电源为系统提供高质量的电源。 URSDR系统接收机由模拟板、频综板、数字板组成。模拟板中,设计合适的放大器、滤波器、开关电路等实现高灵敏度、大增益、宽动态范围和高隔离度。频综板中,用80MHz高稳定、低抖动的时钟作为时钟源；PLL (Phase Locked Loop)芯片产生983.04MHz的时钟参考信号；DDS (Direct Digital Synthesis)芯片产生所需的线性调频信号。FPGA将PLL和DDS的参数预先存放在RAM (Random Access Memory)中,然后以正确的时序写入到芯片中完成配置。数字板中,时钟管理芯片将PLL输出的81.92MHz信号分配给FPGA (Field Programmable Gate Array)作为系统时钟,以及六个C (Analog-Digital Converter)作为采样时钟；ADC芯片具有宽模拟带宽、高采样率、高分辨率,适合对模拟板放大滤波后的回波信号进行射频带通采样；FPGA芯片对采样数据进行数字下变频处理：CORDIC (COordinate Rotate Digital Computer)算法实现正交解调；CIC (Cascaded Integrator Comb)抽取滤波器实现大倍率抽取和滤波；DFT (Discrete Fourier Transform)模块将处理后的时域信号变换到频域。USB (Universal Serial Bus)芯片将数据高速的传输到主机端。主机端程序对数据进行两次快速傅里叶变换(FFT),提取目标的距离和速度信息。 URSDR系统的闭环测试中,通过对-20dBm的射频发射信号延时一定时间来模拟目标的回波信号。接收机对回波信号进行解调、抽取、滤波。经过第一次FFT后得到距离谱,不同的频偏对应不同的距离元,并且相位稳定性在0.080以内,幅度稳定性在0.0025dB以内。经过第二次FFT后得到距离-多普勒谱,由于目标没有运动,因此多普勒峰值应该出现在零频。 2013年3月,URSDR系统在武汉东湖完成了原理性实验,成功验证了河流表面对电磁波散射作用的基本规律。2013年7月,URSDR系统在武汉长江完成了表面流速探测实验。然后建立河流回波谱模型,分析和比对了实测数据和仿真结果,讨论雷达最大探测距离与流速的关系,并绘制径向流图,验证了系统的正确性。
[Abstract]:To fully understand and make full use of freshwater resources, can provide powerful guarantee for national security and economic construction in China. Hydrological instruments used in traditional contact measurement, installation and maintenance of inconvenience; and microwave remote sensing technology is easily affected by the rainfall, fog and other inclement weather effects. Therefore this paper proposes the use of non-contact ultra high frequency of river surface the kinetic parameters of radar (URSDR:UHF River Surface Dynamics parameters Radar) to compensate for these shortcomings.
Doppler frequency shift of UHF radar using water on the formation of Prague scattering of radar waves detection of the river surface using linear frequency modulation continuous wave system work flow.URSDR system to extract the frequency of radial velocity, kinetic parameters of.URSDR system for 340MHz using frequency and phase information of the echo signal, the bandwidth is 15.36MHz, and a frame period is 0.1032s. A coherent time contains 512 frames. Based on the above parameters, the distance of URSDR resolution is 9.77m, the speed of resolution up to 0.0084m/s.
The URSDR system consists of antenna, transmitter, receiver, computer, linear power supply.URSDR receiver is a digital radar receiver, the vibration and the echo signal by mixing FPGA digital terminal of the RF carrier will directly move to zero frequency. Compared with the traditional radar receiver superheterodyne mixer, eliminating the simulation terminal, thus simplifying the system the structure, increase the dynamic range of the.URSDR transmitter the chirp signal is amplified to the power required by the method of "one antenna; six receiving, transmitting and receiving antenna are Yagi antenna can be replaced; the computer used for the initial configuration, data storage; linear power supply high quality power for the system.
The URSDR receiver from the analog board, frequency synthesizer board, digital plate. Analog board, design appropriate amplifier, filter, switch circuit to realize high sensitivity, high gain, wide dynamic range and high isolation. The frequency synthesizer in 80MHz, with high stability, low jitter clock as clock source (PLL; Phase Locked Loop) 983.04MHz chip reference clock signal; DDS (Direct Digital Synthesis) chip to generate LFM signal required for.FPGA parameters of PLL and DDS in RAM (Random Access - Memory), and then to write to the chip in order to complete the configuration. The digital clock management board, chip the distribution of 81.92MHz output signal of PLL to FPGA (Field Programmable Gate Array) as the system clock, and six C (Analog-Digital Converter) as the sampling clock; the ADC chip has wide bandwidth, high sampling rate, high Resolution, suitable for analog board amplification echo signal filtered RF bandpass sampling; FPGA chip to process the sampling data of DDC treatment: CORDIC (COordinate Rotate Digital Computer) algorithm to realize quadrature demodulation; CIC (Cascaded Integrator Comb) decimation filter to realize rate decimation and filtering; DFT (Discrete Fourier Transform) module the time domain signal into frequency domain.USB (Universal Serial Bus) chip high-speed data transfer to the host. The host program of data for the two fast Fourier transform (FFT), distance and speed information extracted from the target.
URSDR closed-loop test system, to simulate the target echo signal through the radio frequency of -20dBm signal time delay. The receiver demodulates the echo signal extraction, filtering. After the first FFT after the distance spectrum, different frequency offset corresponding to different element distance and phase stability, amplitude stability in within 0.080. Less than 0.0025dB. After second FFT after range Doppler spectrum, because no movement, so Doppler peak should appear in the zero frequency.
In March 2013, URSDR completed the principle experiment in Wuhan East Lake and successfully verified the basic rules of.2013 river surface electromagnetic wave scattering effect of URSDR system in July, the Yangtze River in Wuhan completed the surface velocity detection. Then the establishment of river echo spectrum model, analysis of measured data and simulation results and comparison, discuss the relationship between radar detection the distance and velocity, and draw a radial flow diagram, verify the correctness of the system.

【学位授予单位】：武汉大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TN957.5

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