Cylindrical and three-dimensional corner reflector antennas

Two reflector antennas are proposed. The first is constructed by adding a cylindrical reflecting surface of suitable radius to theV-shaped corner reflector antenna. The feeding element is a half-wavelength dipole. The resulting cylindrical corner reflector provided a 2 dB increase in gain, minimum sidelobe level, low input reactance, and uncritical dependence of performance on frequency. The second antenna is constructed by adding a cylindrical surface to the three-dimensional corner reflector. This extension provided an increase in gain of at least 6.5 dB, an input resistance compatible with the commercially available 50- or75-Omegacoaxial cables, low input reactance, and uncritical dependence of performance on frequency. A grid-type cylindrical corner reflector antenna, and a three-dimensional corner reflector antenna with a cylindrical subsurface of finite reflecting surfaces were designed, and the measured input impedances, gains, and field patterns showed excellent agreement with the theoretical results for both antennas.     

The effect of discrete scatterers on a low sidelobe antenna

The effect of randomly distributed scatterers placed in the far field of an antenna is explored. A technique for predicting the effects of specular scatterers on antenna performance has been developed. Laboratory testing of a low sidelobe antenna indicated an acceptable low sidelobe level. However, when the antenna was field tested, it exhibited average radiated power levels off the main beam that were significantly greater than those anticipated. In an effort to determine the cause of this increase, a computer model of an antenna in a field site has been developed, which includes the calculation of the total scattered power of the antenna main beam and sidelobes from specular reflectors distributed over the far field of the antenna.     

一种新型宽带双频段圆极化RFID读写天线

提出了一种新型宽带双频圆极化射频识别(RFID)读写天线,由上层的旋转对称折合振子和缝隙加载的方形贴片以及下层的紧凑型馈电网络构成。天线具有两个外部端口,分别激励低频0.9 GHz和高频2.45 GHz双频段的圆极化辐射。借助HFSS对天线进行了建模、仿真和优化,最后采用FR4板材制作天线实物并完成了试验测试。天线的外部尺寸为0.6λ0×0.6λ0×0.1λ0(λ0为0.9 GHz频点下的自由空间波长),测试结果表明,天线在低频段和高频段的-10 dB阻抗带宽和3dB轴比带宽分别为91.1%(4.9%)和87.8%(1.3%),频段内的峰值增益为5.48 dBic(3.63 dBic),最小轴比为1.1 dB(1.2 dB),在高低频段内,天线的辐射方向图对称稳定。该天线不仅能够满足全球通用型UHF频段(0.84~0.96 GHz)和ISM频段(2.4~2.5 GHz)RFID读写应用需求,而且具有低成本、易加工等优点,在物联网领域将具有很好的应用前景。     

Using hardware gating to improve antenna gain measurements incompact antenna range

Results are presented for antenna gain measurements in a compact antenna range at a frequency below the minimum specified operating frequency of the range. Hardware gating is used to reduce clutter or unwanted scattering from the backlobe of the feed and the walls of the chamber. Measured time domain data are presented which prove that these stray signals can be eliminated from the incident field in the test zone, and frequency data are presented to show the improvement in measured antenna gain     

Suppression of reflections by directive probes in spherical near-field measurements

The influence of probe correction in spherical near-field measurements on signals from outside the test volume is investigated theoretically and experimentally. It is found that the suppression of reflections obtained by a directive probe is not disturbed by the probe correction. A geometric relation between the antenna "minimum sphere" and the probe pattern beamwidth is established, whose satisfaction guarantees the absence of numerical instabilities in the far-field computation. The condition is sufficient, but not necessary if the "minimum sphere" of the antenna is in the near field of the probe.     

卫星定位有源天线性能测试接口转换装置

在卫星有源接收天线测试过程中,受天线自身所带放大器增益的限制,其输出的信号功率无法达到后端测试设备最低输入灵敏度的要求,致使天线的某些性能测试工作无法进行。针对有源天线测试过程中遇到的接口不匹配和接收信号场强不匹配问题,提出了在被测有源天线与后端测试设备之间增加一个接口转换装置。该装置由SMA接头、低噪声放大器、直流电源隔离电路和防浪涌冲击电路构成。仿真表明,该接口转换装置能有效地完成在微波暗室里进行的卫星有源接收天线性能测试。     

基于三相感应电机的小型化超低频发射天线研究

针对低频电磁传输中天线尺寸过大的问题，设计了一种基于三相感应电机的小型化超低频发射天线.电机工作时产生了时变低频电磁场，可作为超低频发射天线.为有效分析其电磁场分布，文章建立旋转磁偶极子数学模型以等效电机内部旋转时产生的磁场.首先，对电机内部磁场和旋转磁偶极子的关系进行阐述，利用麦克斯韦方程组，得到旋转磁偶极子的电磁场分布.其次，通过电磁仿真软件验证旋转磁偶极子的近场分布特性和远场辐射特性.最后，通过实验对电机近场的磁场分布进行验证.仿真和实测结果表明，三相感应电机具有超低频天线的辐射特性.     

D-Fiber antenna characterization using finite-element analysis

An all-fiber antenna using piezoelectric polymer coated circular core D-fiber has been characterized using finite-element analysis. The response of the D-fiber antenna was determined over a wide frequency range from 1 MHz to 2 GWz. The modeling predicts an electric field induced phase shift of 2.43×10^-6 rad/(V/m) per meter at 5 MHz. At frequencies higher than 8 MHz, the optical response is dominated by radial resonances of the D-fiber/coating composite. Using the simulation results, a minimum detectable electric field of 41 μV/m has been achieved using a 1 km length of coated D-fiber. In addition, a D-fiber antenna network intended for microcellular communications has been analyzed using shot noise limited detection. The D-fiber antenna has potential applications in areas such as electromagnetic compatibility testing and radio-over-fiber networks where it provides a convenient means of optically generating radio signals     

地下磁感应通信阵列天线传播特性分析

针对地下磁感应通信系统中单个磁性天线路径损耗大、通信效率低、传输距离短的问题,研究了双线圈天线与3D天线两种协同式天线的电磁传播特性.基于Matlab对根据天线数学模型得到的磁感应强度进行了仿真和分析,并将两种天线的传输性能与单一磁性天线进行了比较.研究表明,两种天线的磁场强度都有很大提高,并具有方向性和对称性,双线圈...     

Antenna Modeling Based on a Multiple Spherical Wave Expansion Method: Application to an Antenna Array

A method to derive an equivalent radiation source for planar antennas is presented. This method is based on spherical near-field (NF) data (measured or computed) to ascertain an equivalent set of infinitesimal dipoles placed over the main antenna aperture. These produce the same antenna radiation field, both inside and outside the minimum sphere enclosing the antenna. A spherical wave expansion (SWE) of the NF data is written in terms of infinitesimal dipoles using a transition matrix. This matrix expresses the linear relations between the transmission coefficients of the antenna and the transmission coefficients of each dipole. The antenna a priori information are used to set the spatial distribution of the equivalent dipoles. The translational and rotational addition theorems are exploited to derive the transmission coefficients of the dipoles. Once the excitation of each dipole is known, the field at any aspect angle and distance from the antenna is rapidly calculated. Computations with EM simulation data of an antenna array illustrate the reliability of the method.      

Low complexity per-antenna rate and power control approach for closed-loop V-BLAST

Previous studies have shown that per-antenna rate and power control can greatly increase the data throughput of vertical Bell Labs layered space-time (V-BLAST), while an extra transmit antenna selection can provide additional diversity advantage. We combine the transmit antenna selection with power and rate control for each antenna. We derive a simple criterion for minimum bit-error rate (BER) or minimum total transmit power when the data throughput is constant over time. Zero-forcing and zero-forcing successive interference cancellation detections are considered. For practical implementation, we also present a fast algorithm that gives near-optimal performance with very low complexity. Simulation results show that the proposed closed-loop BLAST outperforms the open-loop V-BLAST significantly in terms of BER performance, especially when the antennas exhibit strong fading correlations.     

一种超宽带通信系统天线单元的研究

介绍了一种可工作在3~11.4GHz的超宽带平面天线,采用了一级阻抗变换和在接地板上附加梳型槽等方法来展宽天线的带宽,在带宽内方向图基本全向,最小增益为2dB,最大为5.5 dB,体积小、剖面低易于集成,完全适合超宽带通讯系统的需要,具有较高的实用价值。     

一种新型双环宽带圆极化微带天线设计

针对微带天线存在固有频段窄、辐射效率低,且难以获得高增益的问题,设计制作了一种新型双环宽带圆极化微带天线。天线贴片单元采用由槽型环和带状环组成的槽带状结构。槽型环和带状环分别在频率较低部分和频率较高部分各提供一个最小轴比值,通过两个最小轴比值的适当结合达到明显的带宽增强效果。天线利用宽带巴伦结构进行馈电,有效增强了阻抗匹配。通过参数优化和实物制作,仿真与实测结果表明,该天线的阻抗带宽(VSWR≤2)和3 dB轴比带宽分别达到了37%和29.8%,增益达到6.4 dB。     

超宽带超低副瓣相控阵天线时域远场辐射特性研究

本文首先研究了天线时域辐射远场的基本原理,建立了计算公式.在此基础之上,分析了相控阵天线工作在窄脉冲条件下的时域辐射场,发现其时域方向性(如:时域远场峰值方向图、时域远场平均功率方向图)与频域方向性(频域远场方向图)并不一致,这种不一致性随着天线口径的增大或脉冲宽度的变窄而愈加明显,并且在天线注满时间之内表现得尤为突出.文章由此指出:对于超宽带超低副瓣相控阵天线来说,其性能用时域指标去衡量胜于用频域指标去衡量的新观点.     

Further discrete optimizations for continuous aperture illuminations

Two applications of an iterative procedure to establish a means of optimizing theoretical low sidelobe antenna patterns are discussed. Examples described consider discrete element linear array antennas where the parameters involved in the optimization process are coefficients ordinarily associated with continuous aperture illuminations. One application uses the iterative procedure to control far-out sidelobe levels of the far-field pattern to establish array element excitations appropriate for low sidelobe behavior throughout the entire visible region of space. The other application uses the procedure to establish beam port amplitude weightings at a minimum number of beam ports in a multibeam feed network also suitable for low sidelobe antenna pattern behavior.     

Radiation characteristics of slotted oversize patch antennas

A novel integrated antenna with low loss and medium gain is designed. It is composed of a driven oversize slotted patch, backed by a metallic ground plane. Its radiation occurs from the slots and some of its edges. By a suitable optimisation, an excellent field distribution over the antenna aperture is obtained, that provides high gain and low crosspolarisation at far field     

地-电离层波导中甚低频波昼夜过渡期特性研究

建立了地-电离层波导中甚低频电磁波在昼夜过渡期的传播模型,导出了计算昼夜过渡期接收点场强幅度与传播相位的理论公式,分析了季节的改变,白天和黑夜的长短等因素对其产生的影响。理论分析结果表明,接收点的相位昼夜变化近似于一个梯形,其中过渡期的变化即为两个斜边,对应的场强幅度变化出现相应的极大与极小值,而模转换干涉相位偏差即为叠加于斜边上的起伏。实验测试结果证实了理论公式的正确性。     

应用于EMC测量的集成光学电场传感器性能分析

依据集成光学电场传感器的工作原理,研制了可用于电磁兼容性测量的分段电极结构与锥形天线结构的电场传感器.测试结果表明:分段电极传感器频响范围为10 MHz～6 GHz,最小可测电场强度达到30 mV/m,在频率为200 MHz时,线性动态范围可达90 dB;锥形天线传感器频响范围为10 kHz～10 GHz,最小可测电场强度达到20 mV/m,在频率为1 GHz时,线性动态范围可达100 dB.     

Crosspolarisation characteristics of axially symmetric reflectors

The crosspolarisation levels of symmetric front-fed paraboloids and dual-reflector antenna systems have been determined for a wide range of reflector and feed parameters. It is shown that minimum crosspolarisation is achieved when the feed radiates a polarisation-pure field, and, in this case, the front-fed paraboloid is superior.     

三角阵列电极的太赫兹光电导天线结构设计

光电导天线具有室温操作、紧凑设计和宽带辐射等优点,但辐射功率低限制了其广泛应用,其中低光吸收率是辐射功率低的主要原因之一。传统的天线电极无尖端结构,边缘电场弱,导致了低的光吸收率。为了提高光电导天线的辐射功率,设计了一种三角阵列天线电极结构,该电极结构由5个三角形尖端排列组成。使用时域有限差分(FDTD)方法研究了800 nm飞秒激光照射下电极的电场增强和衬底对光的吸收。此结构增加了激光入射到衬底的面积,并且减小了光载流子传输距离,在无电场情况下光的吸收率达到30.57%,相对于传统天线提高了161%。三角阵列电极结构为传统电极结构设计提供了新思路,有望与纳米结构结合进一步提高辐射功率。