天线极化特性的近场测量技术

针对天线极化特性如何在近场测量系统进行测试的问题,文中从实际工程应用出发,结合电磁场理论,基于椭圆极化波的分解理论,提出了利用线极化探头测量椭圆极化天线特性参数的方法。通过线极化探头进行两次正交的测量即可得到圆极化天线的方向图、轴比、倾角、增益等特性信息,也得到了线极化天线的交叉极化特性。     

High‐gain polarization conversion metasurface

A novel analytical method based on the cavity mode theory to design a metasurface (MS) is proposed in this study. We carefully analyzed the phase and amplitude characteristics of the incident wave and transmitted wave, and successfully designed a circular polarization conversion MS by introducing a cutting structure with wider operation bandwidth and higher radiation direction gain compared with that of the original MS. For the measurements, a microstrip antenna operating at 2.4 GHz was used as the source antenna to verify the designed MS. The simulation and measurement results agree well with each other.     

一种小尺寸极化阵列及其高精度定位波束形成

提出一种偶极子天线单元构成的极化敏感阵列用于全球卫星导航信号的接收,经过阵列信号波束形成后,在抗干扰的同时保留卫星导航信号中载波相位测量值的准确性,可用于基于载波相位测量的高精度差分定位。与传统的圆极化天线阵列相比,该阵列具有阵元构造简单、尺寸小的特点。通过建立极化阵列接收信号模型,分析了天线极化和波束形成算法对卫星导航信号相位的影响,给出了相适应的相位中心稳定的数字波束形成算法。仿真验证了分析的正确性和算法的有效性。     

来波极化对鱼骨天线阵低频段波束合成的影响研究

为清晰认知短波定向扇形天线阵,改进阵列波束合成方法,提升波束合成系统性能,利用鱼骨天线阵列模型模拟接收实际不同极化的天波信号,分析阵列合成波束的指向、增益随来波极化和阵列单元数的变化规律,得到在高极化角来波信号时,来波极化补相时阵列的合成波束比按主极化补相时指向更稳定且增益最大可提高2 dB.同时利用实测数据对两种补相...     

Accurate millimeter wave antenna phase pattern measurements usingthe differential phase method with three power meters

The novel differential phase measurement method has been demonstrated at millimeter waves using three power meters instead of a phase-sensitive measurement device. Compared to conventional antenna phase measurement methods, the differential phase method provides several advantages. This method requires no rotary joints or flexible cables. Phase-locking of the oscillators is not necessary. It is shown that the phase measurement device can be replaced by three power dividers and three power meters or detectors. The phase patterns measured with three power meters agree well with the measurements carried out using an antenna measurement receiver as well as with the theory     

一种基于电调移相器的可重构天线

设计并实现了一种基于反射式移相器的极化可重构天线。该天线使用一对交叉摆放的领结型振子作为辐射单元,并在馈电网络中通过两路移相器调整双馈端口间的相位差实现线极化、左旋圆极化和右旋圆极化模式之间的切换。通过加载匹配枝节的方法扩展了反射式移相器的移相范围,提高了移相器的移相精度,降低了天线圆极化模式带内的轴比。所设计天线的中心频率为5.4 GHz,在线极化模式下10 dB 阻抗带宽为990 MHz,在圆极化模式下10 dB 阻抗带宽分别为760 MHz 和850 MHz,3 dB 轴比带宽分别为510 MHz和480 MHz。该天线在频带内具有稳定的波束方向图,其平均增益为5.3 dB,并且具有27 dB 的主极化-交叉极化隔离。最终的实测结果与仿真结果基本一致,表明该天线具有良好的性能。     

一种新型极化捷变有源微带天线阵

本文提出了一种新颖的极化捷变放大器型有源微带天线阵,只要在馈电端电控单一有源电路就能实现整个微带天线面阵极化的捷变和信号的放大.利用角馈方形微带贴片设计了一副具有高隔离度和低交叉极化的新颖16元双极化面阵,并分析了天线阵的共极化和交叉极化方向图.介绍了有源电路的设计.该电路利用一专用电控移相器,通过改变场效应管(FET)栅极的直流控制电压,电控两极化端口间的0°或90°相差,实现天线阵由线极化到圆极化的捷变.低噪声放大器(LNA)不仅使有源天线增益提高12-14dB,而且改善了天线的驻波比带宽和隔离度.文中给出了无源双极化阵和有源阵的实验结果,证实了理论的有效性.     

Comparison of MIMO antenna configurations in picocell and microcell environments

This paper presents the results achieved with a dual-polarized multiple-input multiple-output (MIMO) measurement system in the 2 GHz range. Results from continuous measurement routes were used in evaluating and comparing different MIMO antenna configurations. Different pattern and polarization diversity possibilities were studied using two methods: elements were selected from the antenna arrays used in measurements, and as another option, in the mobile station the incident waves were estimated and used in different dipole antenna arrays. The capacity limit seems to be higher in an indoor picocell than in an outdoor microcell environment. At the mobile station, directive elements result in 35% higher average capacities than those of the omnidirectional elements; however, the capacity of the directive elements also depends on the azimuth direction of arrival of the incident field. Dual-polarized antenna configurations have approximately 14% higher capacities than copolarized configurations. Increasing the number of mobile antenna elements increases the capacity in those environments where the angular spread of the incident field is large. Increasing the distance between elements at the fixed station increases the capacity - especially in microcells where signals arrive from specific directions.     

Phase error and associated cross-polarization effects in cassegrainian-fed microwave antennas

Phase error in the aperture field of a microwave paraboloidal antenna degrades antenna gain in two ways: the asynchronism of partial field contributions arriving at an axial field point reduces the magnitude of the total field there, and the phase error may generate a cross-polarized component of the aperture field that further reduces the axial gain. Because of phase ripples in the field reflected from the subdish, a Cassegrainian-fed antenna may be considerably more susceptible to phase-error effects than conventional focal-point-fed antennas. Consequently, a two-part analysis was conducted to evaluate the importance of these phase-error effects in Cassegrainian systems. The feed-system fields were computed and a best-fit phase center was found. Then the axial gain was computed in terms of the feed-system fields. An expression for the phase-error loss was defined to evaluate the effects of diffractive phase ripple, feed-system misalignment, etc. Numerical analyses were carried out for a wide range of antenna parameters. It was concluded that, for a 19-wavelength subdish and a nearly symmetrical phase and amplitude feed pattern, the loss in axial gain due to diffractive phase error may be only a small fraction of a decibel.     

锥面共形阵列天线盲极化DOA估计算法

 由于共形载体曲率的影响,共形阵列天线中各阵元单元方向图具有不同的指向,使得共形阵列天线具有了多极化特性(Polarization Diversity),为了描述共形阵列天线的多极化特性,通常在共形阵列天线的快拍数据模型中引入阵列入射信号的极化参数,因此共形阵列天线的DOA(Direction-Of-Arrival)估计需要与阵列入射信号极化参数联合估计.本文提出了一种盲极化DOA估计算法,通过在锥面共形阵列天线中设置三对特殊子阵,利用ESPRIT(Estimation of Signal Parameters via Rotational Invariance Techniques)算法,将入射信号极化参数与二维角参数去耦合,在入射信号极化参数未知条件下实现了高分辨DOA估计,并对估计性能进行了理论分析与推导,给出了参数估计的CRB(Cramer-Rao Bound),通过Monte Carlo仿真实验验证了DOA估计算法的有效性.     

C 波段双极化低旁瓣阵列天线

本文设计制作了一种高隔离度低副瓣双极化平板阵列天线,该阵列天线采用角锥喇叭作为辐射单元,以获得 高增益,馈电网络采用空气带状线,以获得较低的馈电损耗,利用探针对喇叭馈电,可获得较高的极化隔离度。在阵 列设计中,采用泰勒加权算法以获得-23dB 的旁瓣,同时利用反相馈电技术使阵列的交叉极化小于-30dB。仿真和实 测结果表明,在6GHz±200MHz 内,驻波小于2,天线增益大于23dB,交叉极化电平小于-30dB.     

On the relationship between the transmitting and receiving properties of an antenna

The response of a linear, passive antenna in free space to an incident plane wave is related to its far-field radiation in the reverse direction bybar{h}^{r}=bar{h}^{t}. The vector effective heightbar{h}^{r}characterizes the voltage across the open-circuit antenna terminals induced by an incident plane-wave field, and the correspondingbar{h}^{t}characterizes the far-field radiation of the antenna when driven by a current injected into the same terminals. This relationship, which is shown to follow from the well-known reciprocity principle, both includes phase and makes mathematically explicit the polarization relation involved in the identity of the transmit and receive patterns of an antenna.     

Antenna-polarization and terrain-depolarization effects on pulse-radar return from extended areas at the near vertical

The methods now in the literature for calculating the terrain-backscattered radar-altimeter echo utilize the antenna power-gain patterns and the terrain radar cross section per unit area, usually designated σ0. In this paper, the polarization characteristics of the antennas and the echo depolarization by the terrain are taken into account for the first time. The formulas for the backscattered return are presented in terms of antenna and terrain parameters that can be measured directly or calculated from other measurements. These parameters are the four transmitting- and receiving-antenna gain patterns for the orthogonal polarization components, the two functions giving transmission- and reception-phase difference between the polarization components, the terrain-depolarization factor that accounts for the average backscattered power cross polarized with respect to the incident wave, and the radar cross section σ0per unit area. It is shown that the older formulas used for radar return from the near vertical are correct only when both antennas are linearly polarized and have the same direction of polarization. The errors that result from failure to consider polarization effects are illustrated by examples.     

Antenna diversity in mobile communications

The conditions for antenna diversity action are investigated. In terms of the fields, a condition is shown to be that the incident field and the far field of the diversity antenna should obey (or nearly obey) an orthogonality relationship. The role of mutual coupling is central, and it is different from that in a conventional array antenna. In terms of antenna parameters, a sufficient condition for diversity action for a certain class of high gain antennas at the mobile, which approximates most practical mobile antennas, is shown to be zero (or low) mutual resistance between elements. This is not the case at the base station, where the condition is necessary only. The mutual resistance condition offers a powerful design tool, and examples of new mobile diversity antennas are discussed along with some existing designs.     

基于RPIM 法的圆极化天线特性参数快速测试

为提高圆极化天线特性参数的测试精度,线极化分量法往往需要对线分量场进行多次测量。文中在天线测试系统中引入插值算法,减少采样点,提高圆极化天线测试效率。将径向基函数的点插值无网格(RPIM)法引入圆极化天线参数合成算法中,首先使用RPIM 拟合出测试场的幅值和相位,然后再使用解析的方式合成圆极化天线的轴比和方向图,算法性能与基于分段线性插值技术的模型参数估计法(MBPE)和基于三次样条插值的移动最小二乘法(MLS)进行比较,数值实验显示,当采样点数仅为测试点数的4%时,MLS 失效,MBPE 和RPIM 误差均为10-3量级;而当采样点数减少为测试点数的2%时,MBPE 和MLS 均失效,RPIM 的误差虽然增大到10-1 量级,但仍能保持稳定。数值实验证明,在采样点数较少情况下,RPIM 性能优于其它两种算法。     

极小极大值法在赋形反射面天线设计中应用研究

为了使星载天线的远场方向图与服务区的形状相匹配,并在服务区内获得高的增益和交叉极化隔离度,通过雅可比-贝塞尔(Jacobi-Bessel)函数来表示反射面的形状,应用极小极大值(MinimaX)算法对单偏置抛物反射面天线进行优化设计.在优化过程中,把表征反射面形状的展开系数作为优化参数,利用物理光学(PO)与物理绕射理...     

The recovery of polarized apparent temperature distributions of flat scenes from antenna temperature measurements

The reception theory for quasi-monochromatic partially polarized emissions is employed to describe the antenna temperature when observing a flat scene from within or above an absorbing/ emitting atmosphere. When the polarization aspects of the antenna and scene are carefully observed, the resulting integral expression for the antenna temperature differs significantly from that reported for polarization invariant temperature distributions. It is observed that the antenna couples to both emitted surface polarizations, and the phase character of the antenna introduces a term involving the product of the polarized and cross-polarized antenna patterns. A matrix approximation of the integral expression is suggested and developed as a means for inverting polarized antenna temperature observations for the underlying partially polarized apparent temperature distributions. The resulting matrix formulation is interpreted and special cases are treated. By means of sample cases, the cross-coupling effect between the antenna and the emitted field polarization vectors is illustrated. When the polarization aspects of the radiometer and the scene are ignored, inversions for the apparent temperature are shown to suffer appreciably even for a highly efficient antenna. The sensitivity of the matrix inversion technique to errors in the measurement vector is also examined.     

宽波束宽角轴比四臂螺旋天线设计

为解决复杂星体环境多径干扰问题,同时满足卫星在轨高速数据传输对测控信道能力的需求,设计了一种带扼流圈的两臂等幅、相位相差90°馈电的四臂螺旋天线.该天线工作在S频段,具有半空间波束覆盖、主向增益高、宽角圆极化性能优异、体积小、质量轻等特性.实测数据表明,该天线圆极化轴比在±110°范围内小于3 dB,仿真与实测结果一致...     

Characteristics of the wire biconical antenna used for EMCmeasurements

The characteristics of a wire biconical antenna that determine its antenna factor were computed by using the method of moments code NEC-2. A fairly extensive validation exercise was conducted from which a suitable computer model was derived. The input impedance, gain, and radiation patterns of the antenna were computed for special cases where the biconical antenna is used above a conducting ground plane for open-field EMC (electromagnetic compatibility) testing. The effects of height above the ground plane and polarization of the antenna on these parameters were found and the antenna factor was corrected for them. The current distribution along the antenna elements was also examined, and it was found that significant pattern distortion can occur at some frequencies when a horizontal wire biconical antenna is used close to the ground. These results will allow this broadband antenna to be used with confidence in applications where previously only resonant dipoles were specified