A low-profile metamaterial absorber with ultrawideband reflectionless and wide-angular stability

An ultrawideband reflectionless metamaterial absorber(MA)is proposed by replacing the metallic ground with the complementary split-ring resonator(CSRR)structure.The proposed MA exhibits-10 d B reflectivity spectrum from 1 GHz to 20 GHz,which maintains more than 90%absorption from 1.5 GHz to20 GHz.Furthermore,it achieves angle stability for TE and TM polarization at oblique incident angles up to 40°and 65°,respectively.To achieve broadband absorption spectrum,we have adopted a single-layer high-impedance surface(HIS)loaded with a double-layer magnetic material(MM)structure.To further realize the RCS reduction into a lower frequency range,we have employed the scattering cancellation technology into the traditional metallic ground.Finally,we have fabricated a sample exhibiting the 10 d B RCS reduction from 1 GHz to 20 GHz with a thickness of 10 mm.Measurement and simulation results confirm that the proposed MA exhibits excellent comprehensive performance,making it suitable for many practical applications.

Monostatic and Bistatic Low Frequency Ultrawideband SAR Imaging Experiment

Low frequency ultrawideband (LF UWB) synthetic aperture radar (SAR) has lately become of a particular interest to SAR community. Monostatic and bistatic LF UWB SAR system has the well foliage penetrating capability, high-resolution imaging and providing the increased information. In 2015, a monostatic and bistatic LF UWB SAR imaging experiment was conducted. In this experiment, the monostatic and bistatic data were collected simultaneously by operating a moving vehicle-based radar in the SAR mode, in conjunction with a stationary ground-based receiver. The aim was to investigate the imaging property of the bistatic LF UWB SAR system. The one pulse per second (1 PPS) signal in combination with the global position system (GPS) disciplined 100 MHz oscillator from the GPS receivers was used to implement the time and frequency synchronization in this SAR system. The bistatic SAR image was obtained by the subaperture spectrum-equilibrium method integrated with the fast factorized back projection (FFBP) algorithm. Bistatic experiment results are show to prove the validity of the bistatic LF UWB SAR imaging experiment.

Study on Stability and Efficiency of High-Power Ultrawideband Radiation Source

Investigations are directed to the development of high-power sources ofUWB （ultrawideband） radiation based on excitation of anterma arrays with bipolar voltage pulses. In the previously designed high-power UWB sources only one bipolar pulse former and different feeder systems for pulse distribution through the array elements were used. By means of this approach, a number of UWB sources were created with the bipolar voltage pulse length ranging from 0.2 to 2 ns and effective potential of radiation ranging from 0.4 to 3 MV. The approach has got a restriction related to the electrical breakdown in a bipolar voltage pulse former. A new approach to the creation of high-power UWB sources based on a multicharmel bipolar pulse former is suggested： the number of bipolar pulse formers is equal to the number of antennas in the array. The main problem in realization of this approach is a stable operation of bipolar pulse formers in order to ensure a coherent summation of radiated pulses in the far-field zone. The result of this work is the instability of-150 ps at the pulse length of 3 ns obtained in a one-channel bipolar pulse former indicating that the suggested approach is realizable.

Metamaterial terahertz device with temperature regulation function that can achieve perfect absorption and complete reflection conversion of ultrawideband

The field of terahertz devices is important in terahertz technology.However,most of the current devices have limited functionality and poor performance.To improve device performance and achieve multifunctionality,we designed a terahertz device based on a combination of VO_(2)and metamaterials.This device can be tuned using the phase-transition characteristics of VO_(2),which is included in the triple-layer structure of the device,along with SiO_(2)and Au.The terahertz device exhibits various advantageous features,including broadband coverage,high absorption capability,dynamic tunability,simple structural design,polarization insensitivity,and incidentangle insensitivity.The simulation results showed that by controlling the temperature,the terahertz device achieved a thermal modulation range of spectral absorption from 0 to 0.99.At 313 K,the device exhibited complete reflection of terahertz waves.As the temperature increased,the absorption rate also increased.When the temperature reached 353 K,the device absorption rate exceeded 97.7%in the range of 5-8.55 THz.This study used the effective medium theory to elucidate the correlation between conductivity and temperature during the phase transition of VO_(2).Simultaneously,the variation in device performance was further elucidated by analyzing and depicting the intensity distribution of the electric field on the device surface at different temperatures.Furthermore,the impact of various structural parameters on device performance was examined,offering valuable insights and suggestions for selecting suitable parameter values in real-world applications.These characteristics render the device highly promising for applications in stealth technology,energy harvesting,modulation,and other related fields,thus showcasing its significant potential.

超宽带低剖面天线设计

介绍了一种超宽带低剖面天线设计,该天线由弯折偶极子、短路寄生结构、接地短路柱、同轴电缆和金属地板构成。给出了天线的设计过程,说明了各部分结构对天线性能的影响。该天线通过加载短路寄生结构,减小了偶极子臂上电流分布,减小了地板对天线的影响,实现了低剖面特性。此外,该天线通过将偶极子中间部分弯折,改善了高频段的辐射方向图。最终,该天线尺寸为750 mm×450 mm×295 mm,剖面高度仅为0.09个低频波长。为了验证天线设计思路的正确性,加工了天线实物。文中给出了天线仿真与测试的电压驻波比以及增益的结果,其测试结果与仿真结果相吻合。该天线在96 MHz~500 MHz(135.57%)频段内电压驻波比小于2.2,并且在该频段内具有定向辐射的方向图,增益大于3.38 dBi。

双层超表面互补增强宽频广角复合吸波体

本文提出了一种基于双层超表面的多层复合吸波体的设计方法,设计的吸波体包含两层核心超表面功能层、顶层吸收增强蒙皮和数层支撑介质层,两层超表面Ⅰ和Ⅱ的结构单元分别为加载贴片电阻的异形金属片和加载贴片电阻的六边形金属环,蒙皮为玻璃纤维层压板,支撑介质为PMI泡沫.仿真结果表明,反射系数低于-10 dB的吸波频带覆盖范围为2.80~23.64 GHz,低于-20 dB的吸波频带覆盖范围为3.56~22.56 GHz.测试结果表明,反射系数低于-10 dB的频带为2.36~23.87 GHz;-20 dB吸波频带为3.17~23.16 GHz.仿真和测试所得反射系数曲线具有良好的一致性,验证了该设计方法的有效性.仿真和测试结果表明,50°斜入射的-10 dB反射系数频带与垂直入射时基本保持一致,起始和终止频率的偏移量小于0.8 GHz;进一步地,斜入射角为60°时,反射系数低于-10 dB的相对带宽最大可达141.8%,表明本研究所设计的复合吸波体具有宽角域入射稳定特性.此外,本文研究了该复合吸波体宽频广角强吸收的相关机理以及主要结构参数对吸波性能的影响,结果表明顶层蒙皮在超宽带范围内可提升吸波率0.2(1.0代表100%吸波),两层超表面吸波频带的互补增强设计能够明显改善其斜入射角度稳定性.

Proposal for All-Optical Switchable and Tunable Ultrawideband Monocycle Generation Utilizing SOA Wavelength Conversion and Time Delay

An all-optical ultrawideband monocycle generator based on wavelength conversion in a semiconductor optical amplifier （SOA） and optical tunable delay in an optical delay line （ODL） is proposed and simulated. The system achieves optically switchable in pulse polarity and tunable in both the pulsewidth and radio frequency （RF） spectrum.

Design of Cross-Shaped CPW-Fed Ultrawideband Slot Antenna

A new design of ultrawideband(UWB) antenna of coplanar waveguide(CPW)-fed is proposed. The antenna is composed of a cross-shaped patch and house-shaped slot with the minimum dimension of 21 mm ×20 mm × 1.6 mm. The analysis of S11, VSWR, radiation pattern and surface current is discussed with HFSS simulation software, and also the effect of parameters is presented. Experimental results show that the bandwidth of the antenna covers 110.67%(3.3—11.6 GHz) of UWB range with return loss better than 10 dB. And the good impedance matching in frequency band confirms the antenna is a good candidate for the application of wireless system.

A Compact Ultra-Wideband Circularly Polarized Antenna Array for Vehicular Communications

In this paper,a new compact ultrawideband(UWB)circularly polarized(CP)antenna array for vehicular communications is proposed.The antenna array consists of a 2×2 sequentially rotated T-shaped cross dipole,four parasitic elements,and a feeding network.By loading the T-shaped cross dipoles with parasitic rectangular elements with cut corners,the bandwidth can be expanded.On this basis,the radiation pattern can be improved by the topology with sequential rotation of four T-shaped cross-dipole antennas,and the axial ratio(AR)bandwidth of the antenna also can be further enhanced.In addition,due to the special topology that the vertical arms of all Tshaped cross dipoles are all oriented toward the center of the antenna array,the gain of proposed antenna is improved while the size of the antenna is almost the same as the traditional cross dipole.Simulated and measured results show that the proposed antenna has good CP characteristics,an impedance bandwidth for S11<-10 d B of about 106.1%(3.26:1,1.57-5.12 GHz)and the 3-d B AR bandwidth of about 104.1%(3.17:1,1.57-4.98 GHz),a wide 3-d B gain bandwidth of 73.3%as well as the peak gain of 8.6 d Bic at 3.5 GHz.The overall size of antenna is 0.56λ×0.56λ×0.12λ(λrefers to the wavelength of the lowest operating frequency in free space).The good performance of this compact UWB CP antenna array is promising for applications in vehicular communications.

光电融合智能太赫兹的体系架构和关键技术

与广泛应用的以微波为代表的无线系统和以光纤为代表的有线系统相比,太赫兹除了其特殊的频谱特性外,人们期待太赫兹频段用于无线系统能突破微波系统的带宽限制,实现可与光纤系统相媲美的大带宽,并具有无线系统的灵活性和智能化。但如何实现宽带、智能以及具有较远作用距离的太赫兹系统,面临极大的挑战性。本文介绍了光电融合智能太赫兹的体系架构,重点讨论了基于光电融合的太赫兹源、接收检测、阵列天线以及太赫兹光电混频器等关键技术的国内外研究进展与进一步发展方向,以期解决单纯的电子学方式或光子学方式存在的难以克服的瓶颈限制。

深度学习融合超宽带雷达图谱的跌倒检测研究

相对于窄带多普勒雷达,超宽带雷达能够同时获取目标的距离和多普勒信息,更利于行为识别。为了提高跌倒行为的识别性能,该文采用调频连续波超宽带雷达在两个真实的室内复杂场景下采集36名受试者的日常行为和跌倒的回波数据,建立了动作种类丰富的多场景跌倒检测数据集;通过预处理,获取受试者的距离时间谱、距离多普勒谱和时间多普勒谱;基于MobileNet-V3轻量级网络,设计了数据级、特征级和决策级3种雷达图谱深度学习融合网络。统计分析结果表明,该文提出的决策级融合方法相对于仅用单种图谱、数据级和特征级融合的方法,能够提高跌倒检测的性能(显著性检验方法得到的所有P值<0.003)。决策级融合方法的5折交叉验证的准确率为0.9956,在新场景下测试的准确率为0.9778,具有良好的泛化能力。

双极化全金属Vivaldi三角栅格阵列设计

本文设计了一个超宽带宽角扫描双极化三角栅格阵列天线,天线采用全金属Vivaldi结构。相较于相同最佳采样的矩形栅格阵列天线而言,采用三角栅格布阵,可以大大减少天线单元数量,降低天线成本。但由于三角形栅格布阵的不对称性,两个极化不完全正交,导致在E面和H面有相比于矩形栅格阵列更高的交叉极化。对基于此结构的无限大阵列进行仿真,该相控阵天线工作带宽9:1(2~18GHz),端口隔离度大于20db,在有源VSWR小于3的情况下,D面、H面扫描角达到±45°,E面扫描达到±30°。

新型电阻膜吸波体在封装辐射抑制中的应用

为抑制封装系统中无意的电磁辐射,设计了一种单元尺寸为0.079λ_(L)×0.079λ_(L)、厚度为0.057λ_(L)的新型电阻膜超材料吸波体结构.该电阻膜超材料吸波体通过在玻璃基板的两侧溅射氧化铟锡薄膜,并在顶层设计图案化的强耦合结构实现了超带宽吸收.通过仿真和实物测试证实了该吸波体结构在17~41 GHz频率范围内具有90%以上的吸收率.为了进一步研究其电磁辐射抑制能力,将该吸波体应用于封装系统模型中,仿真结果显示在18~47 GHz频率范围内3 m辐射电场明显降低,最佳抑制效果达到18 dB.所有结果表明所提出的电阻膜吸波体具有小型化、超宽带、极化不敏感和角度稳定的特性,其良好的辐射抑制能力为封装系统的辐射超标问题提供了新的解决思路.

超宽带圆锥TEM喇叭天线的分析和设计

TEM喇叭是一种超宽带天线,已广泛应用于瞬变电磁场的研究中,本文提出了分析和设计具有波形保真性能的TEM喇叭的新概念和计算方法,介绍了实际制作的加脊圆锥TEM喇叭,并给出了实验结果,表明它具有良好的阻抗特性和波形保真性,对瞬变场和超宽带雷达的研究具有很好的理论和实用价值.

基于二次解析的UWB室内定位高度方向优化方法

针对解析法处理具有高度限制的UWB室内三维定位时的高度方向精度不佳问题,通过对定位方程组的研究,着重分析了其内在原因,并提出了一种基于现有解析法的二次解析法。首先以常见的解析法得到目标点较为准确的水平方向的分量,然后在二次解析过程中采用修正偏差的Tikhonov正则化方法求解优化高度方向的分量。此方法可有效减少目标点高度分量的定位误差以及最终的定位误差。分别通过数学仿真平台和实验平台与传统解析法进行比较,验证了此方法的有效性。仿真与实验结果表明:所提出的方法能够将传统的解析法的定位精度提高40%以上。其中实验结果表明,所提方法的定位效果比最小二乘法提高52.1%,比Chan算法提高41.6%,具有很好的工程应用价值。

新型超宽带微带天线辐射和散射特性研究

提出了一种改进的超宽带微带贴片天线。天线以共面波导方式馈电,其阻抗带宽在满足VSWR〈2.0条件下的仿真计算结果为2.5~20 GHz,天线样机实测结果为2.8~18.7 GHz。研究天线的辐射和散射特性,并与参考天线作对比,发现在同样满足超宽带宽的条件下,设计的天线具有良好的RCS减缩效果。以设计天线为例,分析了超宽带微带天线的散射特性,为超宽带天线雷达截面减缩技术打下了良好的理论和实验基础。

用于公路检测的超宽带横向电磁波喇叭天线

针对沥青路面层厚检测需求,设计了一种简单紧凑的超宽带横向电磁波（Transverse Electromagnetic,TEM）喇叭天线.相对于传统TEM喇叭天线的大尺寸设计,通过采用合理的指数渐变结构以及加载吸波材料,有效地减小了天线尺寸,极大地拓展了天线的阻抗带宽.仿真及测量结果表明：设计的TEM喇叭天线在0.83～12.8 GHz带宽内具有小于2的低电压驻波比,良好的辐射特性和较小的振铃,能够满足路用探地雷达系统要求.

一种改进的小型化超宽带平面倒锥缝隙天线

提出了一种改进的超宽带平面倒锥缝隙贴片天线,通过调整倒锥缝隙和倒锥贴片的形状,在更小尺寸条件下,实现了超宽带性能。天线总体尺寸为40 mm×40 mm×1.5 mm。采用仿真软件分析了该天线的阻抗带宽、辐射方向图及增益特性。结果显示,该天线的回波损耗小于-10 dB的带宽为2.2 GHz到大于16 GHz,在低频段具有全向性,在314 GHz频段增益随频率的变化在47 dB之间。

合成孔径雷达的主要发展方向

首先简要介绍了合成孔径雷达(SAR)产生和发展的历程,其次对当前合成孔径雷达研究的一些主要的热点和发展方向:多参数SAR、干涉SAR、超宽带SAR、激光SAR,尤其是小型化SAR进行了适当的归纳和分析,并且相应地给出了部分具有代表性的SAR系统主要的参数,对合成孔径雷达的研究工作具有一定的理论参考价值。

基于能量检测的脉冲超宽带接收机

在实现一种基于能量检测的脉冲超宽带(IR-UWB)通信系统的基础上对其相应的同步过程进行了深入分析。论证了在一定环境条件下上述系统的最佳传输模式,包括传输速率和数据帧结构,并得出在此模式下系统的有效性和可靠性可达到最优折中。通过实际测量对系统性能进行了测试,验证了最佳传输模式的实用性。结果表明,最佳传输模式的引入可以作为系统设计的重要参考。