一种集总元件加载极端电小折叠单极子天线设计

Design of an Extremely Electrically Small Folded Monopole Antenna Loaded with Lumped Elements

针对无线通信等领域对电小天线的应用需求,设计了一种基于加载集总元件技术的极端电小折叠单极子天线结构。该天线在平面单极子天线的基础上,增加短路枝节拓展电流路径扩展带宽,采用集总元件加载技术,在辐射贴片上串联电阻元件增加输入电阻,并联电抗元件以改善输入电抗,实现了天线的极端电小特性。仿真表明,这种结构可以达到0.053λ×0.022λ×0.0008λ(94 mm×40 mm×1.5 mm,λ为低频170 MHz处的波长)的极端电小尺寸,电压驻波比(Voltage Standing Wave Ratio,VSWR)在170~910 MHz时小于2,具有超宽带特性,并在工作频带内天线都具有良好的全向辐射特性。仿真分析了350 MHz、550 MHz、750 MHz三个频点处的方向图,且对应增益分别能达到-28.8 dBi、-16.7 dBi、-10.4 dBi。加工制作了该极端电小天线模型,实验测试验证了该天线的电小特性和超宽带特性,且方向图和增益测试结果均与仿真结果吻合良好。

To meet the application requirement of electrically small antennas in wireless communication and other fields,this paper designs an extremely electrically small folded monopole antenna structure based on the technology of loaded lumped elements.On the basis of the planar monopole antenna,the antenna increases the short-circuit branch to expand current path and bandwidth.The lumped element loading technology is used to increase the input resistance by connecting resistance elements in series on radiation patch and improve the input reactance by connecting reactance elements in parallel,thus realizing the extremely small characteristics of the antenna.Simulation shows that this structure can reach 0.053λ×0.022λ×0.0008λ(94 mm×40 mm×1.5 mm,λis the wavelength at low frequency 170 MHz),and the Voltage Standing Wave Ratio(VSWR)is less than 2 at 170~910 MHz.It has ultra-wide-band characteristics,and the antenna has good omnidirectional radiation characteristics in the working frequency band.The patterns at three frequency points of 350 MHz,550 MHz and 750 MHz are simulated and analyzed,and the gains can reach-28.8 dBi,-16.7 dBi and-10.4 dBi respectively.The extremely electrically small antenna model is fabricated.Experimental results verify the electrically small and ultra wide-band characteristics of the antenna.And the radiation patterns and gain test results are in good agreement with the simulation results.