一种基于分形结构的超宽带天线研究

基于微带天线和分形天线的基本理论,采用正方形和圆形交替的方法设计了用于超宽带（UWB）通信的分形天线。利用电磁仿真软件CST软件对所设计的天线进行仿真、优化,并分析了影响天线阻抗特性和辐射特性的关键参数。从仿真实验结果可以看出,所设计的天线有较好的全向辐射特性和宽的阻抗带宽,能够满足超宽带通信需求。     

一种宽带天线的研究与设计*

为了满足宽带通信的需求,利用U形单极子天线和两个U形寄生辐射元的方法,设计了一种共面波导馈电的宽带天线,其阻抗带宽达到85%。所设计的天线印刷在尺寸为20 mm×30 mm×1.6 mm、介电常数为265的聚四氟乙烯介质基板上。为了满足无线局域网（WLAN）和全球互联微波接入（WiMAX）的工作需要,抑制不需要的信号,在U形单极子辐射元之间插入一条调谐微带线,产生一个陷波特性,使所设计的天线满足WLAN、WiMAX和低端UWB通信需求。利用高频结构仿真软件HFSS对影响天线性能的主要参数进行仿真、分析和优化,得到天线的优化尺寸,并对优化的天线进行制造和测试。实验结果表明,该天线比传统微带贴片天线性能有了较大的提高,证明了利用共面波导馈电和寄生技术设计宽带天线的可行性和有效性。     

基于微带阵列的天线设计与仿真

研究天线优化问题,为了达到高增益性能,采用天线阵列方法所设计的天线增益在达到一定范围后无法做进一步的提高,带宽偏窄,且占用相当的大小体积.针对上述问题,设计了一款工作于ISM频段的平面微带阵列天线.天线采用的是底边馈电方法对阵元贴片进行馈电,增加天线辐射面积,从而提高天线的增益并减小了天线大小.通过HFSS电磁仿真软件对天线进行仿真与优化,可以得到天线的高增益,并且具有良好的带宽范围.对仿真结果分析可得天线的带宽,增益及方向图性能均要优于传统的的微带阵列天线,空间利用率也高于传统馈电天线,达到优化天线的效果.     

回波损耗补偿在低频段天线测试中的应用与验证

采用间接时域测量技术测试低频段天线时,测试带宽受到天线工作带宽的限制,导致距离分辨率差、无法精确加门,针对这一问题第一次提出利用回波损耗补偿进行带宽扩展的方法,即使扫频带宽大于天线的工作带宽,在后期的数据处理中,将天线的回波损耗补偿到其频域响应上,补偿后的值与天线在整个扫频带宽内无反射、入射能量全部辐射到自由空间时的频域响应相等,达到带宽拓展的目的。对所提出的方法进行了数学模型推导,并在HFSS和Matlab中进行了仿真验证,结果表明经过回波损耗的补偿修正,所得到的方向图与标准方向图相吻合。     

弹载共形遥测天线的设计

设计了一种弹载微带天线,该天线与弹体曲面共形,加上天线罩所凸出的曲面高度不超过8 mm,不仅不影响弹体的动力学特性,而且也不损伤弹体的机械强度。该天线具有较高的增益(8.4 dBi),仿真方向图与实测方向图吻合良好,且在整个工作频段内辐射特性稳定,非常适合作为弹载引信、遥测天线。     

单频段体表/体外双模式可穿戴天线设计

设计了一款5.5 GHz频段基于超表面的宽带方向图分集天线,可应用于单频段体表/体外双通信模式。通过对超表面天线进行特征模分析,选择合适的定向和全向特征模式,修正超表面结构,抑制高次模,设计合适的馈电结构将其激励出来。最后仿真和测试的结果表明,端口1具有全向辐射特性,可用于体表通信模式;端口2具有定向辐射特性,可用于体外通信模式。天线两种模式的工作带宽为23.6%(4.98 GHz～6.25 GHz),带内隔离度高于30 dB。     

矿用可穿戴翻折结构半模衬底集成空腔天线设计

根据煤矿井下对可穿戴天线的要求,在半模衬底集成空腔天线的基础上,采用折叠结构降低天线主体的宽度,并利用水平放置的馈电探针实现可穿戴天线扁平化,设计了一种矿用可穿戴翻折结构半模衬底集成空腔天线。仿真结果表明,该天线在5GHz处于谐振状态,-10dB带宽约为254 MHz,最大增益为5.4dBi,辐射效率为70%,辐射方向具有较宽的主瓣和较低的背向辐射,且可通过增加上层衬底厚度来增加天线-10dB带宽。     

ZigBee精确定位标志卡倒F天线设计

根据ZigBee精确定位标志卡对天线的需求,设计了一种尺寸小、带宽高、辐射效率高的倒F天线。通过电磁场全波仿真软件对倒F天线进行仿真和性能评估,仿真结果表明,该倒F天线工作在2.405~2.484GHz的ZigBee频段内,天线回波损耗小于-10dB;在2.45GHz中心频率下,最大增益达2.5dB,且天线具有全向性。在煤矿巷道中的实际测试结果表明,该倒F天线能满足精确定位标志卡的实用需求。     

多频段圆极化微带天线的设计

设计了一款应用于导航卫星系统的多频段圆极化微带天线。天线采用复合左右手传输线移相器作为馈电网络,展宽阻抗带宽并且实现了良好的右旋圆极化辐射。该天线工作在导航卫星系统GPS、BDS-2和GLONASS工作波段。采用Ansoft HFSS 13.0软件仿真,仿真结果表明该天线能够满足导航卫星信号的要求。该天线具有结构紧凑、频带宽、体积小、易于加工等特点。     

基于HFSS的漏波长槽波导天线的口径场诊断

介绍HFSS在漏波长槽波导天线口径场诊断中的应用,通过合理的子网格设置仿真得到辐射长槽上精确的口径场。采用提取的口径场分布反演得到天线远场方向图,将其与仿真得到的方向图相比,非常吻合,证明这种诊断方法正确有效。根据口径场诊断结果,对天线结构进行调整优化,达到明显的优化效果,天线副瓣明显降低,负载吸收率与理论设计非常吻合。     

A π/4 bi‐orthogonal monopole antenna for operation on and beyond of the UWB band

An ultra‐wideband (UWB) π/4 bi‐orthogonal monopole antenna with a highly omnidirectional radiation pattern in the azimuthal plane with a quasi‐independent on the frequency behavior is presented in this article. Here, it is shown that by combining two orthogonal UWB planar monopole elements rotated 45° with respect to each other in a single structure, it is possible to enhance the performance of the radiation pattern at high frequencies of the operational bandwidth without affecting the radiation pattern at lower frequencies. The measured antenna bandwidth goes from 2.82 to 16.7 GHz for a reflection coefficient lower than ?10 dB. The radiation pattern remains almost omnidirectional, and it is enhanced with respect to a conventional single planar monopole antenna of similar characteristics. The basic element used for both the single and the proposed π/4 bi‐orthogonal UWB planar monopole antenna has a rectangular shape, whose impedance bandwidth ratio is achieved based on the bevelling and height‐width ratio techniques. Although the antenna prototype presented in this article has an operational bandwidth of 13.88 GHz, it is possible to design a UWB monopole antenna with the shape and structure proposed here, but for different bandwidths following a design methodology suggested also in this article. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

Circularly polarized planar monopole antenna for ultrawideband applications

A broadband circularly polarized (CP) planar monopole antenna is proposed here for ultrawideband (UWB) communication. The antenna is composed of a modified annular ring patch fed by a tapered microstrip line and a rectangular semiground plane on the opposite side of the substrate. Capability of generating wide axial ratio bandwidth (ARBW) is another feature of the proposed antenna. Wide ARBW is achieved by introducing a rectangular slot and a stub in the ground plane. The CP antenna has an impressive ARBW of 5.52 GHz (81.42%, 4.02‐9.54 GHz) within the UWB frequency range (3.1‐10.6 GHz). Measured 10‐dB return loss bandwidth of the proposed antenna is 120.86% centered at 7.48 GHz (2.96‐12 GHz). The proposed antenna is well used for wireless local area network (5.2 and 5.8 GHz), Worldwide Interoperability for Microwave Access (5.5 GHz), and other wireless systems in C band as well as CP‐UWB antenna communication.     

High gain CPW‐fed UWB planar monopole antenna‐based compact uniplanar frequency selective surface for microwave imaging

In this article, a novel uniplanar ultra‐wideband (UWB) stop frequency selective surface (FSS) was miniaturized to maximize the gain of a compact UWB monopole antenna for microwave imaging applications. The single‐plane FSS unit cell size was only 0.095λ × 0.095λ for a lower‐operating frequency had been introduced, which was miniaturized by combining a square‐loop with a cross‐dipole on FR4 substrate. The proposed hexagonal antenna was printed on FR4 substrate with coplanar waveguide feed, which was further backed at 21.6 mm by 3 × 3 FSS array. The unit cell was modeled with an equivalent circuit, while the measured characteristics of fabricated FSS array and the antenna prototypes were validated with the simulation outcomes. The FSS displayed transmission magnitude below ?10 dB and linear reflection phase over the bandwidth of 2.6 to 11.1 GHz. The proposed antenna prototype achieved excellent gain improvement about 3.5 dBi, unidirectional radiation, and bandwidth of 3.8 to 10.6 GHz. Exceptional agreements were observed between the simulation and the measured outcomes. Hence, a new UWB baggage scanner system was developed to assess the short distance imaging of simulated small metallic objects in handbag model. The system based on the proposed antenna displayed a higher resolution image than the antenna without FSS.     

A simple planar monopole UWB slot antenna with dual independently and reconfigurable band‐notched characteristics

An extremely simple and compact planar monopole ultrawideband (UWB) slot antenna with dual band‐notched characteristics is proposed. The antenna is composed of a circular radiation patch, a microstrip‐fed line, and a partial ground. By etching an arc‐shaped slot on the radiation patch and a C‐like slot on the feed line, dual notched frequency bands at 3.3–3.7 GHz for WiMAX and 5.15–5.825 GHz for WLAN are achieved. And, the two notched bands can be adjusted independently by varying the length of the slots. Moreover, the band‐notched characteristics can be reconfigurable by shorting the corresponding slots. So, the antenna is capable of operating in one of multiple modes which makes it an excellent candidate for UWB applications. Meanwhile, experimental results indicate that the antenna has an available impendence bandwidth from 2.9 to 11 GHz which covers the UWB frequency band, and nearly omnidirectional patterns, stable gains, small group delay in operating band except rejected bands. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:706–712, 2014.     

Polarization diversity enabled flexible directional UWB monopole antenna for WBAN communications

This article presents the design of an ultra‐wideband (UWB) quasi‐circular monopole antenna with directional characteristics for use in wireless body area network (WBAN) applications. The proposed antenna has hybrid geometry and it is constructed using a semicircular and square patch on a very thin substrate of thickness 0.2 mm. The antenna has a compact geometry with a footprint of 30 × 20 mm. The proposed antenna covers 3.1 to 10.6 GHz with a measured peak gain of 5.37 dBi at 6 GHz. The proximity effect of the human body is resolved by incorporating the reflector behind the antenna. The antenna with reflector provides a directional pattern with a measured peak gain of 8.84 dBi at 6 GHz. Further to improve the link reliability between the sensor and the cluster head in WBAN, polarization diversity technique is adopted and the performance metrics are evaluated. The proposed flexible antenna simultaneously offers large gain and high impedance bandwidth. The prototype antenna is fabricated and the simulation results are validated using experimental measurements. The measurement results are in good agreement with the simulation results.     

A modified split ring resonator based printed compact monopole UWB antenna with spiked elliptical radiator having five band rejection features

A coplanar waveguide (CPW) fed printed compact monopole antenna with five band rejection features is presented. Wide bandwidth was achieved by beveling the lower part and adding a modified ellipse on the upper portion of the patch. An inverted circular arc, single circular split ring resonator (SRR) with wide opening and two symmetrical circular single SRRs were embedded for obtaining three stop‐band characteristics. Two symmetrical slits were inculcated in the ground forming defected ground structure (DGS) to get another stop‐band characteristic. Two concentric rectangular modified SRRs were etched to obtain a higher frequency stop‐band feature. The proposed antenna was designed, fabricated, and experimentally tested for the validation of results. The overall dimensions of the proposed antenna were 29 mm × 24 mm × 1.6 mm. The measured impedance bandwidth of the antenna was 2.87 to 13.3 GHz at | S₁₁ |< ? 10 dB. The measured results show that the proposed antenna has five band notches centred at 3.96, 4.35, 5.7, 8.54, and 9.95 GHz to reject WiMAX band (3.65‐4.04 GHz), ARN band (4.29‐5.18 GHz), WLAN band (5.5‐6.9GHz), ITU‐8 band (7.37‐8.87), and amateur radio band (9.2‐10.3 GHz) respectively. The proposed antenna maintains omnidirectional radiation pattern in H‐Plane and dumbbell‐shape radiation pattern in E‐plane. Further, stable gain over the whole UWB except at notched frequency bands was reported.     

A novel compact self‐similar fractal UWB MIMO antenna

A novel compact self‐similar fractal ultra‐wideband (UWB) multiple‐input‐multiple‐output (MIMO) antenna is presented. This fractal geometry is designed by using iterated function system (IFS). Self‐similar fractal geometry is used here to achieve miniaturization and wideband performance. The self‐similarity dimension of proposed fractal geometry is 1.79, which is a fractional dimension. The antenna consists of two novel self‐similar fractal monopole‐antenna elements and their metallic area is minimized by 29.68% at second iteration. A ground stub of T‐shape with vertical slot enhances isolation and impedance bandwidth of proposed MIMO antenna. This antenna has a compact dimension of 24 × 32 mm² and impedance bandwidth (S₁₁ < ?10 dB) of 9.4 GHz ranging from 3.1 to 12.5 GHz with an isolation better than 16 dB. The various diversity performance parameters are also determined. There is good agreement between measured and simulated results, which confirms that the proposed antenna is acceptable for UWB applications.     

High‐gain dual‐polarized antenna for ultrawideband applications

In this article, a high‐gain and dual‐polarized antenna with UWB operation is proposed. The antenna is composed of two tapered dipoles as radiating elements, which are arranged orthogonally and fed perpendicularly to achieve polarization diversity. A metallic cavity reflector is placed behind the radiator for high gain radiation entire the operating bandwidth. To validate the design method, an antenna prototype is designed, fabricated, and measured. The measured results demonstrate that the proposed design has good performance with |S₁₁| ≤ ?10 dB and isolation ≥20 dB over a frequency band 3.2‐8.8 GHz, equivalently to about 93.3%. In addition, unidirectional radiation pattern and broadside gain of from 8.1 to 11.8 dBi are obtained across the operating bandwidth.