W波段宽带信号的光子收发一体技术研究

Thanks to many advantages of good hiding ability, narrow beam, wide bandwidth, high Doppler frequency, small size, light weight, etc., W-band millimeter wave (MMW) is an ideal candidate for applications to inter-satellite communications, satellite meteorology, and MMW radar. Although electronics technology matures, there exists an "electronic bottleneck" limitation for performance improvement due to its low bandwidth, high loss, and timing-jitter. In this project, we propose a novel scheme of W-band MMW coherent transceiver-receiver system by full use of broad bandwidth, low loss, and low timing-jitter of photonics technology. This scheme utilizes only one mode-locked femtosecond laser source with low timing-jitter and wide spectral bandwidth for both generation and receiving of W-band linearly chirped pulse signal with wide bandwidth, ensuring high coherence and measurement precision. Signal generation unit consists of the laser source and unbalanced fiber dispersion chirp, which enables simultaneous tunability of W-band MMW’s central frequency, bandwidth, and time duration and also improves the anti-interference ability of the system. Based on low timing-jitter of the laser source, a pure local reference is generated for mixing and down-conversion of the received W-band signal generation. Later, the time-stretch photonic analog-to-digital conversion (ADC) technology is adopted for dramatically compressing the down-converted W-band signal and reducing the bandwidth requirement of electronic ADC. In recent years, we have undertaken in advance some related theoretical and experimental studies, verifying the feasibility of this project. It is believable that the smooth and successful implementation of this project with high technical specifications and reliable study conditions guarantees the cutting-edge technology for our major national security.

W波段毫米波具有波束窄、频带宽、体积小、重量轻等诸多优点，被用于星间通信、卫星气象观测及雷达探测等。电子学技术日趋成熟，但受带宽、损耗、时钟抖动等“电子瓶颈”限制，进一步提升面临挑战。本项目发挥光子学的大带宽、低损耗、低抖动等优势，围绕“毫米波光子高稳定协同作用和收发系统高相参机理”和“非线性作用下的毫米波光子信号失真和精细调控机理”关键科学问题，提出W波段宽带信号的光子收发一体的原创方案。采用一台飞秒激光器既产生又接收W波段的线性调频脉冲信号，确保系统相参和测量精度。融合激光器宽谱和非平衡色散，产生频率、带宽和时宽均可调的W波段宽带信号，提高抗干扰能力。信号接收时，首先基于激光器低抖动特性产生基准源进行混频下变频，然后基于时间拉伸的频谱压缩技术，降低电模数转换带宽。近年来已开展较充分的前期研究，夯实了相关的理论和实验基础。深入开展本项目的基础科学研究，可为国家重大安全提供尖端技术储备。

W波段(75-110GHz)作为高频毫米波，支持的信号带宽大和传输速率高，可分别采用电子学或光子学的手段来实现，被广泛应用于卫星间通信、卫星气象观测以及毫米波雷达探测等领域，线性调频脉冲信号是W波段毫米波和微波雷达系统的理想选择。近年来电子学技术发展迅猛、日趋成熟，但受带宽、损耗、电采样时钟抖动和比较器模糊等“电子瓶颈”限制，进一步提升面临很大挑战。据此，本项目有机融合光纤锁模激光器、非平衡色散啁啾和时间拉伸等光子学手段，实现W波段毫米波宽带信号的光子收发一体技术：基于锁模脉冲在光纤中的非平衡色散啁啾效应实现W波段宽带的线性调频脉冲信号的产生，基于光纤色散的时间拉伸实现W波段宽带信号的接收和处理。发射系统和接收系统基于相同的锁模光纤激光器，可确保信号产生和处理过程的高度相参，从而大幅提高宽带系统的测量精度。本项目重点研究W波段宽带信号的光子收发系统的高相参实现方法，紧紧围绕毫米波光子链路、信号产生、信号接收和信号处理等方面，对W波段毫米波的宽带信号光子收发一体的关键技术进行攻关，研制一套W波段宽带信号的收发一体实验平台。具体研究内容包括：毫米波光子链路，宽带信号产生，宽带信号接收，宽带信号处理等。主要技术指标包括：工作频段85~105GHz，调频带宽≥10GHz，时间宽度≥100ns，信号形式为线性调频脉冲，工作模式为中心频率、带宽、时间宽度均可调。在完成各项指标的前提下，我们还对实验平台上的系统进行了封装，研制成了宽带雷达的发射机和接收机，构成了完整的雷达原理样机系统。授权国家发明专利6项、国际专利5项。在国际光纤通信顶级刊物上发表论文20篇以上，参加ICOCN等国际会议，并做受邀报告，培养博士研究生2人，硕士研究生11人。通过本项目的基础科学研究，有望为我国的星间通信、卫星气象观测以及毫米波雷达探测等国家重大安全领域提供尖端技术储备。

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