Creeping waves on a perfectly conducting cone

The rigorously formulated scalar and vector Green's functions for a perfectly conducting semi-infinite cone are approximated asymptotically to furnish the high-frequency creeping wave contributions when the source and observation points are both located on the cone surface. The results are expressed in the ray-optical format of the geometrical theory of diffraction and thus provide another canonical solution for verification of the postulates of that theory. The analytical procedure for isolating the creeping waves from other high-frequency phenomena such as tip diffraction is motivated by the methodology for the simpler circular cylinder problem, to which the present solution reduces when the cone-to-cylinder transition is performed. The results are of interest for calculation of source-induced surface currents, and of mutual coupling between slot array elements, on conical surfaces.     

倒锥微孔阵列的激光微加工技术研究进展

激光微加工技术凭借其加工效率高、加工材料广泛、无物理损伤以及操控性强等优点在高精度机械部件的加工上有较好的应用前景,易加工出尺寸微小、数量庞大、高品质的倒锥微孔阵列.首先对激光加工微孔的工作原理和特点进行了介绍,综述了激光在加工微孔阵列、倒锥微孔以及倒锥微孔阵列的研究现状,详细介绍了准分子激光、飞秒激光、纳秒激光在加工...     

强相干干扰下基于二阶锥规划的圆弧阵宽带二维成像

该文针对水下目标2维成像在强相干干扰情况下,目标亮点容易被淹没的问题,以及圆弧阵波束的高旁瓣给图像检测带来较多虚警的缺陷,提出基于二阶锥规划的宽带2维成像优化方法。该方法在对相干干扰抑制的同时,很好地控制了波束的旁瓣。分析了2维成像算法流程中由于时域滑窗导致阵列的接收信号矢量与阵列流形不同,造成二阶锥规划设计的权值与阵列的接收信号矢量失配,旁瓣控制和零陷设计无法满足设计的要求。针对该问题提出利用计算出的滑窗理论阵列的接收信号矢量代替阵列流形来进行二阶锥权值设计的方法,通过改进的二阶锥权值,将波束优化与圆弧阵的2维成像优化相结合。计算机仿真和水池实验都验证了该方法的有效性。     

A cross LPD array antenna on a conducting cone

A cross LPD array antenna on a conducting cone has been designed and tested. The frequency-independent characteristics of the LPD array antenna were maintained by coinciding the virtual tip of the LPD array and that of the conducting cone. It was found that the radiation pattern and the input impedance of this antenna are not significantly deteriorated by the presence of the conducting cone.     

Convex optimization based beam-space preprocessing with improved robustness against out-of-sector sources

Beam-space data preprocessing is a powerful tool commonly used in array processing to reduce the computational burden and improve the performance of high-resolution direction-finding algorithms. However, currently used beam-space techniques appear to lack robustness in the presence of sources that are located outside the beam-space angular sectors-of-interest. In this paper, a new approach to beam-space preprocessing with an improved robustness against such out-of-sector interfering sources is developed. Our techniques design the beam-space matrix filter based on proper tradeoffs between the in-sector (passband) source distortion and out-of-sector (stopband) source attenuation. Computationally efficient convex formulations for these beam-space matrix filter design problems are derived using second-order cone (SOC) programming.     

Mutual coupling analysis of arrays of apertures on cones

The analysis of the element pattern in an array of waveguide elements on a cone is approached by systematically exploiting the geometrical symmetry of the structure. The method consists of decomposing the arbitrary array excitation into fundamental excitations (eigenexcitations) for which the solution of the electromagnetic problem is simpler than in the general case. Following Bailin and Silver, the fields external to the cone are represented as a superposition of modes TE and TM to the radial direction. For each eigenexcitation the fields in the waveguide elements are represented as a superposition of normal waveguide modes. The enforcement of the continuity of the electromagnetic fields at the conical interface provides complete information about the radiation from the elements and the reflection coefficients of the modes in the waveguide. The array element pattern is obtained by the superposition, with suitable weights, of the patterns of the eigenexcitations. The communication presents the computational procedures followed to evaluate with high speed and precision the roots of the Legendre functions necessary to represent the fields external to the conical structure. Numerical results for the realized element patterns of a particular conical array are presented in the final section.     

Modeling semi-anechoic electromagnetic measurement chambers

Previous studies developed a model to predict theoretically the low-frequency plane-wave reflection coefficient of an array of pyramid cone absorbers such as those used to line anechoic electromagnetic measurement chambers. The present authors apply this model in a geometrical optics approach to predict the electromagnetic field in a chamber lined with cone absorbers in the frequency range of 30-300 MHz. The results are compared with site attenuation measurements for two actual semi-anechoic chambers     

柔性稀疏阵的稳健波束形成

本文将导向矢量失配时的稳健波束形成问题归结为二次锥规划问题,利用高效的内点法求解。该波束形成器成功地应用于存在阵元位置误差的柔性稀疏阵,相对于经典的对角线加载法、特征空间法,在不同的输入信噪比下获得了更好的输出信号干扰加噪声比。仿真结果表明对超稀疏分布的柔性阵,阵元位置误差对输出SINR起决定性影响,而阵列稀疏程度对其影响不大。     

一种稀疏表示的二维DOA降维估计新算法

提出了一种基于空间锥角降维的二维DOA稀疏分解估计新方法,解决了利用稀疏表示方法进行二维DOA估计时计算复杂度大的问题.根据L阵列的结构特性,引入空间锥角表示信号的二维DOA信息,构造空间锥角冗余字典,通过稀疏正则化求解实现空间锥角的估计,然后利用求解得到功率实现L阵列中两个子阵之间的空间锥角配对,从而达到对多来波的二维DOA估计的目的,其避免了方位角和俯仰角组合而造成冗余字典庞大的问题,极大地减少了稀疏分解的计算量.仿真和实测数据结果均验证了该方法的有效性和优越性,为进一步的工程应用奠定了基础.     

X波段矩形波导相控阵天线

本文给出X波段矩形波导相控阵天线的研制结果。将该天线作为电磁场边界值问题求解,建立了以孔径切向电场为未知函数的积分方程。经矩法处理后,在DJS-6型电子计算机上得到了数值解。制作了115元的无源小阵列。测量了阵单元方向图,加工了两个H面波导模拟器:HIC14和HIC29,进行了测试。宽角匹配介质板和孔径上匹配膜片的参数是通过理论计算和试验调整确定的。理论计算结果与测量结果相近。在86009600MHz频段和60扫描圆锥体内,天线的输入电压驻波比VSWR2。     

基于二阶锥规划的矢量阵波束优化设计及仿真

提出了将二阶锥规划方法应用于矢量阵的波束优化设计。该优化方法在保证波束旁瓣低于期望值的条件下,设计以最小加权均方误差逼近于期望波束响应的波束。将该优化设计方法转换为二阶锥规划形式．通过已有的内点方法求出其数值解。计算机的仿真结果验证了基于矢量阵得到的优化波束具有较好的稳健性．另外由于SOCP在波束优化设计方面具有其本身的优越性,可以通过增加约束表达式兼顾多个性能指标的设计。     

Slotted waveguide linear array with polarisation control

The design of an experimental dual-mode waveguide linear array antenna is described and measurements on a 10-element model are presented. The antenna comprises a `notched? wall dual-mode waveguide containing an array of suitably located transverse/longitudinal slot pairs. Polarisation control is achieved by feeding the array through a 3 dB hybrid followed by a phase shifter.     

期望主瓣响应下任意阵方向图综合方法

为实现任意阵列天线的方向图综合,特别是考虑到不同空间指向对阵列方向图的影响,提出自适应原理与凸优化理论相结合的方向图综合法.该方法首先利用自适应原理综合法得到所需阵列方向图的旁瓣特性;而后,选择零度角的方向图主瓣作为期望主瓣;最后,在该期望主瓣响应下,将阵列方向图综合问题转化为二阶锥规划问题.采用凸优化循环迭代算法,完成对非凸优化问题的求解,从而保证方向图在满足期望主瓣响应的同时,使旁瓣特性与自适应方向图综合方法得到的结果最接近.理论分析与仿真结果表明,综合后阵列方向图在不同空间指向上具有与期望主瓣一致的主瓣特性,且其旁瓣也能够很好地保持对动态干扰的抑制特性.     

双锥共线阵天线辐射特性

双锥共线阵天线因其宽频带,高辐射功率等特点被广泛应用于工程中,文中采用基于有限元法的电磁场仿真技术对双锥共线阵天线进行辐射特性研究,分别通过改变阵子个数,锥角等参数研究其辐射特性与各参数变化的关系。然后根据导航设备的实际需要设计出一种满足国际民用航空公约附件十要求的双锥共线阵天线,实验结果表明,该天线适用于陆基导航系统中测距机的信标天线。     

Robust Adaptive Beamformers Based on Worst-Case Optimization and Constraints on Magnitude Response

In this paper, novel robust adaptive beamformers are proposed with constraints on array magnitude response. With the transformation from the array output power and the magnitude response to linear functions of the autocorrelation sequence of the array weight, the optimization of an adaptive beamformer, which is often described as a quadratic optimization problem in conventional beamforming methods, is then reformulated as a linear programming (LP) problem. Unlike conventional robust beamformers, the proposed method is able to flexibly control the robust response region with specified beamwidth and response ripple. In practice, an array has many imperfections besides steering direction error. In order to make the adaptive beamformer robust against all kinds of imperfections, worst-case optimization is exploited to reconstruct the robust beamformer. By minimizing array output power with the existence of the worst-case array imperfections, the robust beamforming can be expressed as a second-order cone programming (SOCP) problem. The resultant beamformer possesses superior robustness against arbitrary array imperfections. With the proposed methods, a large robust response region and a high signal-to-interference-plus-noise ratio (SINR) enhancement can be achieved readily. Simple implementation, flexible performance control, as well as significant SINR enhancement, support the practicability of the proposed methods.     

硅基有序截锥短纳米线的陷光特性

高效陷光是提高薄膜太阳电池效率的重要因素。本文利用周期性的截锥Si纳米线结构获得了宽光谱的高效陷光,其陷光机制借助FDTD solution软件进行了分析。利用图形衬底和选择性外延技术,先在硅衬底上生长出传统的周期性圆柱状硅纳米结构,长度为200nm,直径为80nm;之后利用热氧化技术,制备出可控的截锥纳米线结构,长度为140nm时,其在300-900nm的平均反射率低于5%。这表明有序截锥短纳米线具有良好的宽光谱减反特性,可应用于径向纳米线太阳电池的制备。     

二阶锥规划问题的等价关系及应用

介绍二阶锥规划的概念、数学模型,研究并推导了各种标准形式的等价关系。在此基础上介绍了二阶锥规划在信号处理中的应用,并着重以阵列天线加权设计为例,利用二阶锥规划理论来实现期望的阵列加权设计,通过仿真给出了设计结果,结果表明这种设计方法是有效的。     

快慢时间域间歇采样转发干扰生成进动锥体ISAR群阵列

为了提升空间锥体目标突防能力,该文提出一种基于快慢时间域间歇采样转发干扰生成沿距离向及方位向分布的空间锥体ISAR群阵列方法。首先分析了双站情况下空间锥体目标ISAR像成像方法;针对线性调频波分析了快慢时间域间歇采样生成空间锥体ISAR群阵列的基本原理及其ISAR假目标分布特性。最后结合电磁仿真数据,分析了快慢时间域间隙采样参数对ISAR群阵列分布的影响,可为ISAR欺骗式干扰提供参考。     

锥状微结构阵列提高OLED出光效率的研究

为提高OLED出光效率,在OLED基底上设计锥状微结构阵列,通过几何光学和光线追迹方法分析了锥状微结构对OLED出光效率的影响。结果表明:锥状微结构阵列最大可以提高60%的出光效率;锥状微结构阵列的占空比、材料折射率和坡度角对出光效率有较大影响;锥状微结构阵列不会改变OLED的辐射角,且有一定的聚光作用。结果为提高OLED出光效率提供一种新的参考和方法。     

Radiation and scattering from isorefractive bodies of revolution

The radiation from an electric or magnetic dipole located on the symmetry axis of an isorefractive body of revolution (BOR) and axially oriented is considered. The boundary-value problem is solved exactly for three BORs: the isorefractive prolate and oblate spheroids and the isorefractive paraboloid. Furthermore, for the isorefractive circular cone, the radiation from an arbitrarily located and radially oriented dipole, and the scattering from an obliquely incident plane wave are determined exactly