Accordion shape monofilar axial mode helix for RFID reader

An accordion shape monofilar axial mode helical antenna designed by curving the helix along the axis is proposed. This antenna achieves a low-profile characteristic as the 10-turn helix's axial length is 0.354/spl lambda/. The impedance bandwidth (SWR<1.5) is 9% from the frequency of 880 to 963 MHz and the axial ratio bandwidth (AR<3 dB) is 6.5%. The measured gain is 10.2 dBi. This antenna operated at the centre frequency of 915 MHz and has a tilted radiation of 17/spl deg/ to the curving side.     

Coaxial-feed axial mode hemispherical helical antenna

A coaxial-feed axial mode hemispherical helical antenna is studied experimentally and theoretically. Results for a 3-turn hemispherical helix indicate that circular polarisation can be obtained over a broad beamwidth. The gain bandwidth is ~33% and the peak gain is 7.6 dB. The input impedance shows that it is a standing wave antenna     

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.     

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。     

Truncated spherical helical antennas

The truncated spherical helix is presented as a compact circularly polarised antenna with relatively high gain and moderate bandwidth. A numerical investigation into the radiation properties of this antenna is also presented. The antenna provides a directivity of >9 dB and an axial ratio of <3 dB over a 10% bandwidth. The radiation pattern has a broad main beam and better than 20 dB front-to-back ratio     

A printed hemispherical helical antenna for GPS receivers

A self-matched printed hemispherical helical antenna for potential use in global positioning system receivers is introduced. Unlike wired hemispherical helical antennas, its printed form renders it a much more stable and endurable structure and also easier for fabrication. The optimized antenna shows an impedance bandwidth of 6%, a 3-dB axial ratio bandwidth of 6%-7%, a return loss greater than 20 dB, and a gain of about 9 dB at the center frequency. The patterns of the antenna show a larger mainlobe in the upper half space with relatively small backlobes. Both theoretical and experimental results was presented.     

一种超宽带半球柱面螺旋天线的研究

研究了一种等弧距单臂半球柱面螺旋天线，其具有宽带、小尺寸、圆极化、低剖面等特点.该天线采用半球柱面螺旋天线结构，通过在馈电端引入等效L节匹配网络进行阻抗变换，扩展天线带宽，最终实现了天线的小型化、圆极化及超宽带.利用HFSS仿真软件对半球柱面螺旋天线结构参数进行优化，仿真及测试结果表明，该天线具有超过30%的阻抗带宽及超过20%的轴比带宽，最高增益能够达到9 dB，具有良好的辐射特性.     

Mechanically Tunable Multiband Compact Quadrifilar Helix Antenna With Dual Mode Operation

We show that by introducing a gap at the center of the helical sections (where the current is minimum) of a lambda/2 quadrifilar helix antenna (QHA) and varying the axial length and radial gap between the overlapping volutes, the antenna gives a 28% impedance bandwidth which is nine times the bandwidth of a conventional QHA. A 16% bandwidth with a front to back ratio of ges 14 dB is achievable with 5-14% reduction in the size of the QHA. The structure can yield a monopole radiation pattern suitable for terrestrial applications or a hemispherical pattern suitable for satellite use. The simulation results are validated by measurements at L-band.     

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。     

Tapered backfire helical antenna with loaded termination

In order to improve the radiation characteristics of a backfire bifilar helical antenna, a means of terminating the arm ends with a resistor is numerically and experimentally investigated. Owing to the reduction of reflected current, the present backfire helix realises an excellent front-to-back ratio and axial ratio, while maintaining inherent absolute gain.     

一种寄生阵列宽带圆极化天线的设计

该文设计了一款C波段单馈寄生阵列的宽带圆极化天线。此天线采用紧邻的双层F4B介质基板,通过在方形驱动贴片上开槽及采用寄生阵列的设计实现了圆极化。对天线结构的设计步骤进行说明,研究了各结构对天线阻抗带宽和轴比带宽的影响,并研究了寄生贴片切角长度和驱动贴片上的缝隙宽度对天线轴比和带宽的影响。对天线的圆极化方向图进行了仿真。仿真结果表明,在5.5 GHz时实现了右旋圆极化,最大增益为8.1 dBi。加工并测试了宽带圆极化天线,测试结果与仿真结果基本相符,天线实测的阻抗带宽为1.3 GHz,轴比带宽为1.26 GHz。设计的叠层天线具有结构紧凑,装配简单和轴比带宽大的优点。     

Theory of the frequency responses of uniform and quasi-taper helical antennas

A theory is presented for the frequency responses of uniform and quasi-taper helical antennas radiating in the axial mode. Based on a model assuming a single traveling wave of current, expressions for the far-zone electric field are obtained by summing the contributions of the current elements from one end of the helix to another. These expressions are used to study the variation of the axial electric field with frequency, first assuming the Hansen-Woodyard (HW) condition and then assuming Sensiper's solution for the phase velocity. It is found that the HW condition leads to the result that the electric field increases monotonically with frequency over the entire axial mode range, which is in violation with the recent experimental measurements of King and Wong. On the other hand Sensiper's phase velocity yields frequency response curves that are consistent with King and Wong's measurements. Numerical results are given for uniform helices and quasi-taper helices consisting of two uniform sections of different diameters.     

Broadband printed circularly-polarised aperture antenna array for millimetre-wave gigabit applications

A simple and successful design of a printed aperture antenna array is presented in view of high-speed millimetre-wave wireless access applications. The antenna element design is based on a broadband travelling- wave aperture antenna for circularly-polarised radiation. For the antenna array design, the sequential rotation scheme is employed for improving the co-polarised gain and axial ratio. The presented antenna array is designed in the 40?48 GHz band and implemented with a 5mil-thick RT/Duroid-5880 PCB. Promising performances are achieved, including a return loss (,10 dB) bandwidth of 32%, an axial ratio (,3 dB) bandwidth of 25%, and a co-polarised gain (flatness , 3 dB) bandwidth of 32% with a maximum gain of 11dBic.     

宽带高增益圆极化微带天线与阵列

设计了一副宽带高增益圆极化微带天线,并进行组阵分析。天线中心频率2.6 GHz,通过增加寄生贴片和空气层来提高天线单元的增益和带宽。上下两层介质板上边长不同的切角方形贴片分别激励一个低频与高频的圆极化模,有效地拓宽了轴比带宽。仿真结果表明,反射系数|S11|<-10 dB带宽21.8%,3 dB轴比带宽12.0%,中心频率点增益9.0 dBi。对天线单元进行加工测试,与仿真结果较为吻合。设计了2×4元阵列,并进行了仿真,增益提升至17.5 dBi,3 dB轴比带宽10.4%。     

用于无线局域网的轴向模螺旋天线设计

根据无线局域网通信天线的要求,设计了三种工作在5GHz频段性能良好的轴向模螺旋天线,其中一种为普通螺旋天线,第二种为加绕寄生螺旋天线,第三种为锥形加绕寄生螺旋天线。通过电磁仿真软件HFSS计算及对结果分析表明,加绕寄生螺旋将改善天线的轴向辐射特性,而锥形结构将扩展天线带宽。     

一种新颖的宽带圆极化单极天线

该文设计了一种新颖的宽带圆极化单极子天线,该天线采用微带馈电模式。天线由C型贴片和改进的地板组成,整个天线尺寸仅为25×25×1 mm3。通过在C型贴片上切角和在地板上增加三角形微扰结构,可以有效增加天线的阻抗带宽和轴比带宽。该文给出了天线的设计流程,从表面电流分布分析了圆极化天线的工作机理。加工了天线实物,并对其进行了测量。仿真和实测结果表明天线具有超宽的阻抗带宽和轴比带宽。天线的工作频带为4.35～12 GHz(相对带宽为93.6%),3 dB轴比带宽为4.15～11.8 GHz(相对带宽为95.9%)。测量了天线的辐射性能和增益特性,实测结果与仿真结果吻合较好,证明了该天线的有效性。该天线可以应用于超宽带无线通信系统和卫星通信系统中。     

A backfire helical feed

A novel backfire helical feed for a paraboloidal reflector is described. The antenna requirements were a 20 percent bandwidth atL- band, right-hand circular polarization, a maximum voltage standing-wave ratio (VSWR) of 2.0, and a peak power capability of 200 kW unpressurized. The feed consists basically of a 3.5-turn helix wound around a1frac{5}{8}-in rigid coaxial transmission line. The50 Omegatransmission line is coupled to the helix through a two-stage transformer within the coax followed by a half-wave coax to two-wire (unequal diameters) balun.     

一种小型化宽带圆极化微带天线的设计

设计并加工了一种采用同轴背馈方式馈电的小型化宽带圆极化微带天线。针对单点馈电微带天线轴比带宽窄的问题,通过增加馈电网络对天线辐射贴片进行双点馈电以展宽轴比带宽,得到了良好的效果。馈电网络根据带状线理论设计,利用U形接地板巧妙地实现了宽带天线的结构小型化。通过对辐射贴片的双点馈电获得了令人满意的电压驻波比带宽和良好的圆极化性能。通过仿真和实际测试表明,该天线VSWR≤2的带宽达到了30％,3dB圆极化带宽约为26％,同时频带内天线的增益达到4dB。     

Printed quadrifilar resonant helix antenna with integrated feedingnetwork

A compact printed quadrifilar resonant helix antenna with integrated feeding system is presented. This antenna displays small size, low cost, hemispherical radiation coverage, large bandwidth, good efficiency and good axial ratio     

Broadband circularly polarised hexagonal slot antenna excited by a tapered microstrip feeder

In this article, a broadband circularly polarised slot antenna fed by a single microstrip line is implemented. The proposed antenna is composed of an unequilateral hexagonal slot to implement circular polarisation and tapered microstrip feeding line to enhance the impedance bandwidth. A conducting reflector is also employed to enhance the antenna gain. The proposed antenna, 60 mm × 60 mm × 18.12 mm in size, was fabricated and tested. The measured??10 dB reflection bandwidth and 3 dB axial ratio bandwidth were 48.9% and 17%, respectively. The measured gain of the fabricated antenna ranged from 5.4 dBi to 6 dBi within an axial ratio bandwidth of 3 dB.