A method to modify the Ultra Wideband ( UWB )monopole antenna is proposed to improve its performance.By adding a segment of arc on the ground plane and changing the right angles of the ground plane to fillets,the current distributions of the antenna is changed,the impedance characteristics is improved and the bandwidth is broadened,covering the bandwidth of the ultra wideband that is stipulated by Federal Communication Commission.Tvie antenna is simulated by electromagnetic simulation software An-soft HFSS,and in the last the radiation patterns of this antenna are given, with the simulation results indicating that the improved antenna is nearly achieved omnidirectional radiation at a lower frequency and also shows the design is practicable and effective.%为了改善平面超宽带(Ultra Wideband,UWB)单板子天线的性能,提出了在天线的接地板上引入圆弧形切口和将方形接地板的直角改成圆角的设计方法,经过此方法改进后的天线其表面电流分布发生了改变,天线的阻抗特性得到改善,工作带宽进一步扩展,完全覆盖了美国联邦通信委员会(FCC)规定的超宽带工作频段(3.1～10.6)GHz.采用电磁场仿真软件Ansoft HFSS对天线的性能进行仿真,并绘制天线的方向图,仿真结果表明改进后的天线在较低频率几乎实现了全向辐射的方向性,同时也为验证了此改进方法的可行性及有效性.
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