Wideband radar cross section reduction using a novel design of artificial magnetic conductor structure with a triple‐layer chessboard configuration

A novel wideband three‐layer chessboard‐like structure is proposed to reduce the radar cross section (RCS) of the radar target. This configuration is composed of two artificial magnetic conductor (AMC) cells formed by two crossed ellipses with different sizes in two cells. A desired 180° ± 37° phase difference is achieved by combining these unit cells and the measured 10 dB RCS‐reduction bandwidth is extensively broadened to more than 96% (from 8.11 to 23.32 GHz, covering X, Ku, and K bands for different radars) in comparison with the other works. This characteristic is obtained by carefully adjusting the positions of all resonances using the proper sizes for the ellipses and the proper dielectric constants and thicknesses for the three layers. Although, the proposed design has three layers with the overall thickness of 2 mm, it is still thinner than most of the recent related works. This low‐profile structure is also cost‐effective due to the fact that 60% of the overall thickness is formed by an air substrate. The proposed cells are designed, simulated, and fabricated in a chessboard‐like configuration for both monostatic and bistatic RCSs. Simulations and measurements are in a good agreement, which shows the capabilities of the design.     

大空间双模多频段射频识别复合定位

针对室内大范围射频识别定位,提出一种双模多频段射频识别复合定位方法。被定位对象同时携带有源和无源两种模式的标签,微波频段阅读器与被低频频段信号激活的有源标签通信,根据有源标签信号区域选通超高频频段读写器天线,以减轻读写器天线之间干扰;以固定时间读写器天线对无源标签的收包次数为定位参数,在被定位对象位置计算过程中分区筛选最大后验概率位置并利用欧式距离修正定位坐标,完成贝叶斯概率定位算法的改进。实验验证表明,本文提出的复合定位方法,不但可以改善大空间定位中读写器天线间的干扰,而且与LANDMARC算法相比较,定位误差降低59.86%。     

雷达射频隐身技术研究与发展

在分析雷达及其对抗技术发展现状的基础上,阐述了雷达系统射频隐身技术的概念及其重要性;通过对射频隐身基本原理的研究,提出从雷达射频辐射的时、频、空和能等多维空间上进行控制,并与作战环境相融合等研究方向与方法,为开展具有隐身性能的雷达装备研制和技术研究提供参考。     

一种多带多chirp基调制解调技术

多带线性调频二进制开关键控(Chirp-BOK)调制是在线性调频(Chirp)信号基础上合成的,其传统的检测方案匹配滤波法存在非相关项自干扰问题,在子带个数较多或Chirp基的时带宽积较小情况下误码性能较差。建立了一种多带Chirp信号的数学模型并提出一种简易的调制框图,基于该模型,采用最小二乘法解决了匹配滤波法自干扰问题,相比于匹配滤波法,具有较好的信干噪比增益。更进一步地,通过分析多带Chirp-BOK技术缺陷提出一种多带多Chirp基调制技术(MMCM)。MMCM技术可以灵活地调整码率与扩频增益之间的关系。仿真表明,扩频增益为0dB情况下,MMCM与OFDM技术有相同频带利用率;对于MMCM的信源组个数为J与时带宽积为P的情况,系统处理增益为P/J。     

RF/wireless-interconnect: The next wave of connectivity

In the era of the nanometer CMOS technology, due to stringent system requirements in power, performance and other fundamental physical limitations (such as mechanical reliability, thermal constraints, overall system form factor, etc.), future VLSI systems are relying more on ultra-high data rates (up to 100 Gbps/pin or 20 Tbps aggregate), scalable, re-configurable, highly compact and reliable interconnect fabric. To overcome such challenges, we first explore the use of multiband RF/wireless-interconnects wh...     

面向分级设计优化的飞行器参数化建模方法

针对飞行器气动隐身外形综合设计优化问题,提出合适的面向分级设计优化流程,建立适应该流程的渐进分层参数化建模方法;用基于敏度分析的参数影响程度分析方法筛选复杂设计变量;采用多学科设计优化（Multidisplinary Design Optimization,MDO）理论和差分进化算法进行飞行器气动隐身外形的综合设计优化.将该方法用于某飞行器外形设计优化,结果表明：该方法合理可行,可为飞行器外形多学科设计优化提供一定参考.     

多带模拟信号的采样与重构

为了实现多带模拟信号的有效采样,根据多带模拟信号的特点,建立了一个在平移不变空间上的多通道采样模型;利用插值函数实现信号的完整重构。以多带正弦信号为例,验证了该系统可以实现多带模拟信号的采样与重构。     

Phosphorylcholine polymer nanocapsules prolong the circulation time and reduce the immunogenicity of therapeutic proteins

Protein therapy, wherein therapeutic proteins are delivered to treat disorders, is considered the safest and most direct approach for treating diseases. However, its applications are highly limited by the paucity of efficient strategies for delivering proteins and the rapid clearance of therapeutic proteins in vivo after their administration. Here, we demonstrate a novel strategy that can significantly prolong the circulation time of therapeutic proteins as well as minimize their immunogenicity. This is achieved by encapsulating individual protein molecules with a thin layer of crosslinked phosphorylcholine polymer that resists protein adsorption. Through extensive cellular studies, we demonstrate that the crosslinked phosphorylcholine polymer shell effectively prevents the encapsulated protein from being phagocytosed by macrophages, which play an essential role in the clearance of nanoparticles in vivo. Moreover, the polymer shell prevents the encapsulated protein from being identified by immune cells. As a result, immune responses against the therapeutic protein are effectively suppressed. This work describes a feasible method to prolong the circulation time and reduce the immunogenicity of therapeutic proteins, which may promote the development and application of novel protein therapies in the treatment of diverse diseases.

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红外隐身防护材料研究进展

目的 综述近年来国内外先进的红外隐身防护材料技术的研究进展,并对红外隐身材料的未来进行展望。方法 从红外探测技术与红外隐身原理出发,着重介绍低发射率材料、控温材料、新型智能红外隐身材料以及协同复合材料等一系列有优异性能的材料。结果 红外隐身可通过降低物体表面温度及降低物体表面辐射率来实现,依据这两方面原理研制的红外隐身防护材料具有良好的隐身效果。结论 不同种类的红外隐身材料具有不同的特点,已广泛运用于军事装备、织物等方面,但依然存在一些不足,未来要针对不同应用环境要求进一步优化,以期满足现代化战争需求。