光学真时延相控阵接收机关键技术研究

发布时间：2019-05-07 07:30

【摘要】：相控阵雷达相比传统雷达具有波束扫描快等优势,已得到广泛的应用,然而由于存在孔径渡越时间的缺陷,只能在相对窄带的情况下工作,限制了其在现代战争中复杂环境下的应用。本文设计的光学相控阵天线将传统相控阵结合微波光子学,通过光学真延迟的方法补偿了孔径渡越时间,实现了微波信号在光域的延迟移相与合成,提高了雷达的瞬时带宽,消除了宽带雷达信号下的波束偏斜效应。本文系统性研究了光学相控阵天线的设计,并对实验样机进行了测试,对今后光学真时延相控阵的设计与实现有着一定的参考价值。本文从相控阵波束形成的原理出发,推导了相控阵的移相网络幅相误差对形成波束指向及波束增益的影响,同时从理论上解释了传统相控阵波束偏斜产生的原因及真时延结构带来的优点。本文也对光学相控阵系统中最根本的光载射频(RoF)链路进行了数学建模,根据模型推导了链路各项性能指标的理论表达式,并介绍了提高链路性能的方法。最终根据这两部分理论分析提出了光学相控阵天线系统的设计方案及对器件参数的优化选择。光纤可变延迟线作为光真时延移相网络的最基本单元其精度决定了相控阵的性能。本文提出了一种拥有高成功率的新型高精度延迟光纤制作工艺,设计了光纤精密研磨平台及基于此平台的高精度光纤延迟线制作流程。其制作过程中长度的精确测量由矢量网络分析仪(VNA)完成,最小精度受限于VNA的相位测量的不确定度,达到0.1 mm。提出光辅助并行时间交替采样模数转换技术方案及其通道失配误差的估计和修正方法,实现了在光学相控阵天线的接收端对雷达回波信号直接射频采样,并使用高采样率示波器完成了对该方案的实验验证。实验实现了四通道并行采样,等效采样率达到了40 GSas-1,在6.31 GHz测试信号下信纳比为40.3 dB,无杂散动态范围为57.6 dBc,对应有效位数为6.4位,达到示波器的上限。完成了8阵元光学相控阵天线样机在2-4 GHz频段内的性能测试,其中单路全光RoF链路的频段内最小的射频增益为-39.5 dB,最大噪声系数为40.3 dB,最小三阶无杂散动态范围为93.2 dB·Hz2/3。光纤延迟线插入损耗校准为7 dB,最大幅度均方根误差为0.55 dB,最大时延均方根误差为0.4 ps。排除外接模块引入的误差后测得波束指向精度在±40°扫描角时最大均方根误差仅为0.35°。测试结果表明了光纤延迟线幅度相位的精度以及对应波束指向角精度达到了相对较高的水准,同时此光学相控阵天线系统克服了波束偏斜效应,提高了系统的瞬时带宽。
[Abstract]:Compared with traditional radar, phased array radar has been widely used because of its advantages such as fast beam scanning. However, due to the defect of aperture transit time, phased array radar can only work under relatively narrow band conditions. It limits its application in the complex environment of modern warfare. The optical phased array antenna designed in this paper combines the traditional phased array with microwave photonics, compensates the aperture transit time by optical true delay method, realizes the delay phase shift and synthesis of microwave signal in optical domain, and improves the instantaneous bandwidth of radar. The beamforming effect of wideband radar signal is eliminated. In this paper, the design of optical phased array antenna is systematically studied, and the experimental prototype is tested, which has certain reference value for the design and realization of optical real time delay phased array in the future. In this paper, based on the principle of phased array beamforming, the influence of amplitude and phase error of phased array on beam direction and beam gain is derived. At the same time, the reason of beamdeflection of traditional phased array and the advantages of true delay structure are explained theoretically. In this paper, the mathematical model of the most fundamental optical-borne RF (RoF) link in the optical phased array system is also presented. According to the model, the theoretical expressions of the performance indexes of the link are derived, and the methods to improve the link performance are introduced. Finally, the design scheme of the optical phased array antenna system and the optimum selection of the device parameters are put forward according to these two parts of theoretical analysis. As the most basic element of the optical true delay phase shift network, the precision of the optical fiber variable delay line determines the performance of the phased array. In this paper, a new type of high precision delay fiber fabrication technology with high success rate is presented. The optical fiber precision grinding platform and the manufacturing process of high precision fiber delay line based on this platform are designed. The precise measurement of the length in the fabrication process is completed by the vector network analyzer (VNA). The minimum precision is limited by the uncertainty of the phase measurement of the VNA, reaching 0.1 mm.. An optical-assisted parallel time-alternating sampling analog-to-digital conversion scheme and its channel mismatch error estimation and correction method are presented. The direct RF sampling of radar echo signal at the receiving end of the optical phased array antenna is realized. A high sampling rate oscilloscope is used to verify the scheme. The four-channel parallel sampling is realized in the experiment. The equivalent sampling rate is up to 6.31 GHz and the equivalent sampling rate is 40 GSas-1,. At 6.31 GHz, the SNR is 40.3 dB, the spurious free dynamic range is 57.6 dBc, and the corresponding effective bit is 6.4 bits. Reach the upper limit of the oscilloscope. The performance test of 8 element optical phased array antenna prototype in 2 ~ 4 GHz band has been completed. The minimum RF gain in the band of single-channel all-optical RoF link is-39.5 dB, and the maximum noise figure is 40.3 dB,. The minimum third order non-spurious dynamic range is 93.2 dB 路Hz2 / 3. Fiber delay line insertion loss calibration is 7 dB, maximum amplitude root mean square error is 0.55 dB, maximum delay root mean square error is 0.4 ps. After removing the error introduced by the external connection module, the maximum root mean square error is only 0.35 掳when the beam pointing accuracy is at 卤40 掳scanning angle. The test results show that the precision of amplitude and phase of the optical fiber delay line and the direction angle of the corresponding beam reach a relatively high level. At the same time, the optical phased array antenna system overcomes the beam skew effect and improves the instantaneous bandwidth of the system.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN957.5

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