带异形反射腔和寄生螺旋的均匀升角轴向模螺旋天线

为了改善轴向模螺旋天线的辐射特性,在带有寄生螺旋的均匀升角轴向模螺旋天线基础上,设计了一种带有曲反射面背腔的螺旋天线,并用HFSS软件对天线的辐射特性进行了仿真分析。通过对比几种不同形式的螺旋天线的仿真结果,证明了该种螺旋天线可以有效地提高轴向模螺旋天线增益系数,圆极化一致性良好,是一种提高轴向模螺旋天线性能的有效方法。     

基于有限元方法的螺旋天线设计

研究了一种用于中短距离通信的螺旋天线,分析了螺旋天线特别是轴向模螺旋天线的基本电磁辐射特性,介绍了有限元方法的基本理论和数值计算过程,并结合有限元法对螺旋天线进行了设计、优化,仿真出该天线的电参数和辐射方向图,然后将设计的天线模型进行通信实验。实验表明圆极化的轴向模螺旋天线通信质量良好,完全达到设计要求。     

基于矩量法的螺旋天线设计

螺旋天线具有宽波束、圆极化等特性。以往的轴向螺旋天线多为端射式,辐射方向单一。为弥补这一不足,提出了一种新型的中馈轴向螺旋天线。基于RWG(Rao-Wihon-Glisson)边元的矩量法,采用MATLAB仿真计算出中馈螺旋天线的方向图、反射系数、增益等重要参数。又利用高频结构仿真软件(HFSS)对所设计的中馈螺旋天线进行了仿真。通过两种方法仿真得到的结果吻合较好,仿真结果的正确性得到了验证。实验结果表明:中馈轴向螺旋天线不仅具有以往轴向螺旋天线所具备的定向性好和高增益等优点,还具有两个反向且强度相同的辐射方向,同时天线增益可以达到8dB以上,半功率波束宽度可达33°。这种天线可以应用到多边通信及中继通信等领域。     

轴向模螺旋天线方向性系数分析

传统的轴向模螺旋天线的方向性系数公式只考虑了螺旋直径、螺距及圈数等几个变量,忽略了反射板的尺寸和形状以及馈电方式对方向性系数的影响。简要介绍了轴向模螺旋天线的工作原理,仿真计算了反射板的尺寸和形状以及馈电方式等几个变量与螺旋天线的方向性系数的关系,加工制作了其中一种天线。实测结果与仿真结果基本一致,因此验证了仿真结果的正确性。为轴向模螺旋天线的设计提供了有价值的参考。     

短螺旋天线改进设计

以提高天线功率容量为目标,提出了短螺旋天线的改进方案,数值模拟了螺旋主要结构尺寸对其辐射特性和最大场强的影响,给出了具有较高功率容量的短螺旋天线模型.工作频率为4.0 GHz时,改进后的短螺旋天线轴向方向性系数为8.75 dB,轴向轴比为1.22 dB,真空状态下的功率容量提高到64MW.将该单元天线应用到了高功率螺旋阵列天线的设计中,通过对阵列天线的实验测量说明了短螺旋单元天线的良好性能.     

机载螺旋天线辐射特性的研究

本文用螺旋的半圆近似法计算了阿基米德螺旋天线的辐射场。应用几何绕射理论（ＧＴＤ）导出了机载螺旋天线辐射场的计算公式。计算结果与实测结果进行了比较，两者吻合较好。     

基于粒子群算法的低副瓣螺旋天线设计

提出了一种单绕低副瓣螺旋天线的设计方法. 在单绕螺旋天线外加一个金属锥面来改变天线的辐射特性. 采用粒子群算法对影响天线方向图的参数,包括金属锥面两端的口径和长度进行了设计,以降低天线辐射方向图的最大副瓣电平. 仿真分析和实验测试结果说明在要求的1268.5±10 MHz频带范围内该天线驻波比小于1.15,天线方向图的最大副瓣电平低于-25 dB.     

频率可重构的液态金属锥形螺旋天线的仿真设计

为设计多频带GNSS天线且具有体积小、高增益、可重构、易于保密等特点的圆极化天线,提出一种频率可重构的液态金属锥形螺旋天线。天线可应用于卫星导航系统,包括GPS,GLONASS,BDS-2B1和BDS-1S系统。采用HFSS软件对天线进行设计与仿真,并利用仿真软件的优化功能对天线进行阻抗匹配,得到了良好的圆极化辐射和阻抗特性。仿真结果表明,天线在设计的两个频段内,增益大于3 dB,轴比均小于3 dB。因此,所提出的频率可重构的液态金属锥形螺旋天线具有非常广阔的应用空间。     

高功率双层径向线螺旋阵列天线理论分析与数值模拟

研究了一种高功率双层径向线螺旋阵列天线.论文首先介绍该阵列天线的工作原理,然后从工作原理出发,设计中心频率为4.0 GHz的高功率双层径向线螺旋阵列天线,提出并研究了螺旋单元天线的磁耦合馈电,最后用有限元算法软件对阵列天线进行了数值模拟.模拟结果表明:该口径为320mm的天线在中心频率上可获得21.13dBi的增益,口径效率可达72.3％,在-12°≤θ≤12°的范围内轴向轴比值小于1.55;在3.8GHz~4.2GHz的频率范围内增益大于20.68dBi,口径效率大于69%,天线轴向轴比值小于1.7.     

一种宽带宽波束移动终端卫星通信天线

提出一种实用型宽带宽波束移动终端卫星通信天线。该天线采用双臂渐变螺旋以及锥形反射板的结构提高了常规双臂螺旋天线的性能。结合HFSS 软件与理论分析进行了天线结构参数设计,并进行了仿真和实验。仿真结果与测试结果吻合良好。该天线采用左旋圆极化方式,中心工作频率为1. 6GHz,工作频带150MHz,波束宽度大于110毅,且天线结构简单、牢固、易于加工,适合于各类小型移动卫星通信终端,以及高纬度地区的卫星通信。     

Axial mode helical antennas

The radiation characteristics of helical antennas operating in the axial mode are evaluated on the basis of the theoretical current distributions and are verified by experimental work. A comparison between monofilar helix and bifilar helix antennas is made, and a helical antenna with a parasitic helix (HAP) is proposed in order to enhance the power gain. It is found that the gain of the HAP in which the parasitic helix is wound from a point diametrically opposite to that of one and one-half turns of the driven helix is about 1 dB higher than that of the monofilar helix. The ratio of the frequency band in which the HAP radiates a circularly polarized wave within an axial ratio of 3 dB is calculated to be 1:1.8.     

球面螺旋天线的研究

研究了一种新型的球面螺旋天线,与传统螺旋天线相比,具有结构紧凑、尺寸小、增益高的特点,分析了两种不同模式下球面螺旋天线的辐射特性和输入阻抗;并首次提出了一种工作在圆锥模式下的半球面螺旋天线,具有更小的尺寸和良好的赋形波束,可应用于近地卫星通信。     

Broadband quasi-taper helical antennas

A unique approach is described for widening the bandwidth of a helical antenna with improved gain, pattern, and axial ratio characteristics. The antenna may be described as a nonuniform or quasi-taper helix, which consists of a combination of uniform and tapered helix sections. Measured patterns, gain, axial ratio, and VSWR for various helical antenna configurations are presented and compared. It is shown that a nonuniform quasi-taper helix can provide an operating bandwidth twice that of a conventional uniform-diameter helix.     

Modeling of normal-mode helical antennas at 900 MHz and 1.8 GHz formobile communications handsets using the FDTD technique

A simple technique is proposed for modeling short normal-mode helical antennas using a commercial finite-difference time-domain (FDTD) code with a rectangular grid and a nominal extension of the wire. The approach allows affects on the input impedance and radiation performance of the helix to be examined and importantly does not require modification of the excitation subroutines. Normal-mode helical antennas for mobile communications use at 900 and 1800 MHz were designed using the proposed method and good agreement with measurements of impedance and near-magnetic field strength was found. The radiating performance of the helix was compared to that of a λ/4 monopole and generally found to be inferior at 900 MHz due to only 19.2 % efficiency in the presence of the head. At 1.8 GHz the two antenna types showed similar characteristics except in regard to bandwidth, 36.1 % for the monopole and 7.8 % for the helix, in the presence of the head. The modeled helix antennas produce spatial peak specific absorption rate (SAR) figures that are up to 27 % greater at 900 MHz and up to 49 % greater at 1.8 GHz than the corresponding monopole values due to the shorter antenna     

电磁脉冲下螺旋天线瞬态响应的仿真研究

由于通信天线经常工作在宽带或者多频带模式,为了对电磁干扰下的通信天线进行保护,对天线时域特性的仿真必不可少.其中一个需要研究的问题就是将天线装载于金属平台上并同时使用脉冲源激励.文中使用一种具有通用性的数值方法--时域电场积分方程,仿真了电磁脉冲照射下螺旋天线的宽带瞬态响应特性.采用拉革尔多项式作为全域时间基函数来展开时间变量,获得求解线天线散射辐射问题的时域电场积分方程,也就是阶数步进递推格式,最后使用数值计算得到了螺旋天线的瞬态响应特性.     

Human proximity effects on circular polarized handset antennas inpersonal satellite communications

Satellite-based systems are the next step in mobile communications. Several low and medium Earth orbit mobile communication satellite systems have been proposed and are currently being deployed. For all these systems, high-performance circularly polarized antennas for the mobile terminals are of importance. Although considerable material is available on circularly polarized antennas, there is an absence of information on how the human's close proximity to the antenna affects the circular polarization purity of the radiated field. This paper presents an analysis of representative circularly polarized helical handset antennas. The helix is used because of its wide bandwidth properties and capability to provide both circular and linear polarization. Thus, this element could be used for handsets that are planned to work with both the terrestrial-based communications systems of today and the satellite-based communication systems of tomorrow. The intent is to characterize the effects the close proximity of a human head model has on the computed performance of the circular polarized antenna. The method of moments (MoM) and finite-difference time-domain (FDTD) numerical techniques are used to study various helix structures on top of a small box representing a handset. In order to be able to effectively apply the FDTD, a novel square helix structure is introduced. Results computed with these two techniques are compared to illustrate the accuracy of each implementation. The results indicate significant polarization purity degradation caused by the presence of a human head. For the particular geometry simulated, the presence of a head model degraded the average axial ratio within a 50° vertical cone from 2.9 to 9.1 dB. This significant increase in axial ratio can have profound effects on link budgets