利用收发宽波束实现星机双基地SAR的波束同步

由于低轨道雷达卫星的飞行速度远快于飞机,波束同步技术是关系到星机双基地SAR能否具有实用价值的核心技术。已有文献中提出的基于收发波束指向控制的同步方法具有场景长度短、算法复杂等缺点。根据星机双基地SAR远发近收的特点,提出一种基于收发宽波束的波束同步方法。从信噪比、系统模糊性等方面对该方法进行量化论证。仿真结果验证了方法的可行性。与已有方法进行比较,结果表明,文中提出的方法能在方位分辨率相等的前提下获得更大的场景长度;而且由于无需进行波束指向控制,成像算法简单。     

在轨运行热环境下的天线镜面热变形对空地激光通信链路的影响

针对光学天线镜面热变形对空地激光通信链路性能产生影响的问题进行了理论和仿真分析。采用ANSYS有限元分析软件仿真得到的结果表明：低轨卫星在轨运行热环境条件下，采用潜望式结构且暴露在卫星舱外的光学天线反射镜镜面热变形将导致天线镜面法向偏转，其偏转量在不能释放热应力条件下可达几十μrad量级，经其传输的光束将产生较大的指向偏差；对所提出的释放热应力效果较好的天线镜体安装方式进行的相应分析表明：镜面变形受到镜体固定方式的影响非常大，在一定的参数条件下，和压板法固定方式相比较，压圈固定方式受到热变形影响形成的法向角度偏转较小。     

先进焊接技术在飞机制造中的应用

通过对国外飞机制造公司焊接技术的应用分析,明确了先进焊接技术——电子束焊、激光焊和搅拌焊技术的应用现状和使用范围,并结合西飞公司的实际情况,提出应该发展电子束焊和激光焊接技术,以弥补未来制造能力的不足;同时应重点关注搅拌摩擦焊接技术的发展动态,掌握国外该技术的应用状况和使用经验。     

An optimal beam alignment method for large-scale distributed space surveillance radar system

Large-scale distributed space surveillance radar is a very important ground-based equipment to maintain a complete catalogue for Low Earth Orbit (LEO) space debris. However, due to the thousands of kilometers distance between each sites of the distributed radar system, how to optimally implement the Transmitting/Receiving (T/R) beams alignment in a great space using the narrow beam, which proposed a special and considerable technical challenge in the space surveillance area. According to the common coordinate transformation model and the radar beam space model, we presented a two dimensional projection algorithm for T/R beam using the direction angles, which could visually describe and assess the beam alignment performance. Subsequently, the optimal mathematical models for the orientation angle of the antenna array, the site location and the T/R beam coverage are constructed, and also the beam alignment parameters are precisely solved. At last, we conducted the optimal beam alignment experiments base on the site parameters of Air Force Space Surveillance System (AFSSS). The simulation results demonstrate the correctness and effectiveness of our novel method, which can significantly stimulate the construction for the LEO space debris surveillance equipment.     

基于载波相位的多通道相位一致性测量方法CSCD

对于卫星导航系统,由导航天线进行波束合成的多路并行导航信号需要具有严格的相位一致性,本文给出基于专用地检设备的多通道相位一致性测量方法。该地检设备采用载波相位辅助伪码测距技术,通过载波相位和伪码相位的联合解算,实现了伪码相位对载波相位解整周期模糊,最终测距精度达到1ps。采用该测试方法对系统进行配相,实现了各通道无周期模糊的相位一致性。     

应用激光测振技术提高模态试验测量准确度

以一个标准直梁为研究对象,应用扫描式激光测振系统对梁进行了模态测量,得到梁的弯曲振动和纵向振动固有频率和振型,光测结果与理论计算结果相符。与传统的传感器测量结果相比,激光多普勒测振技术测量准确度高,可以很好的解决传感器对结构产生的附加质量的问题,尤其适用于轻薄结构的模态测量。     

基模高斯激光束高倍率扩束实验研究

基于激光光学设计了一个适合实验室环境的高倍率激光扩束系统,并进行了相应的实验研究。实验结果表明束腰半径为0.295mm的激光束,最大被扩束至束腰半径约12.04mm。     

一种图像指令传输系统天线方案

文章分析了波束切换天线系统的工作原理,介绍了一种S频段图像指令传输系统天线的方案设计。     

ICAN: A novel laser architecture for space debris removal

The development of a fiber based laser architecture will enable novel applications in environments which have hitherto been impossible due to size, efficiency and power of traditional systems. Such a new architecture has been developed by the International Coherent Amplification Network (ICAN) project. Here we present an analysis of utilizing an ICAN laser for the purpose of tracking and de-orbiting hyper-velocity space debris. With an increasing number of new debris from collisions of active, derelict and new payloads in orbit, there is a growing danger of runaway debris impacts. Due to its compactness and efficiency, it is shown that space-based operation would be possible. For different design parameters such as fiber array size, it is shown that the kHz repetition rate and kW average power of ICAN would be sufficient to de-orbit small 1–10 cm debris within a single instance via laser ablation.     

Q/V频段电磁波在等离子体鞘套下的传输特性

高超声速飞行器再入地面时,由于飞行器表面等离子体电子密度分布不均匀,因此从背风面向天基中继卫星传输,可避开迎风面的高电子密度,并以Q/V频段为测控频段,经中继卫星转发至地面测控站。本文以波阻抗方法为基础,分析了Q/V频段在不同等离子体参数下的传输特性,并仿真了等离子体对Q/V频段天线波束指向的影响。结果表明：Q/V频段在等离子体中穿透性更好,可在更高的等离子体电子密度和碰撞频率下保持较低的衰减值。但Q/V频段下的天线波束指向偏差较大,随着频段的提高和入射角度的减小,偏差值逐渐减小。因此,应用Q/V频段,通过中继卫星转发实现实时通信,有利于缓解再入飞行器“黑障”现象。