ABSTRACT

An ultra-wideband (UWB) antenna with quadruple-band-rejection characteristics and a size-miniaturised approach for portable wireless applications is designed and experimentally investigated. The proposed antenna consists of a unique trapezoidal-shaped patch, 50 Ω triple-step microstrip feed line and step–truncated ground plane. The patch tapering improves the bandwidth of an antenna to 2.8–12.5 GHz with fractional–bandwidth of 127%, covering an entire UWB (3.1–10.6 GHz). Consequently, it provides a nearly omnidirectional radiation pattern, better gain and excellent radiation efficiency. The three steps of the feed line increase the electrical length of the patch, achieving size reduction of the fabricated antenna to 20 mm × 29 mm. Generally, UWB systems suffer owing to strong narrowband signal interference from unlicensed wireless communication devices. To avoid this, the proposed antenna is designed with quadruple band-notch characteristics. It includes three inverted U-slots (length approaches half the guided wavelength), which are used to reject the 3.5, 4.5 and 5.2/5.8 GHz bands. Moreover, a C-strip pair besides the feed line is used to reject the 8.35 GHz X-band. The simulated results were also compared with the experimental performance of the prototype in terms of reflection coefficient, voltage standing wave ratio, radiation pattern, transfer function, group delay and gain of the antenna.

摘要

设计并实验研究了一种具有四频带抑制特性的超宽带 (UWB) 天线和一种用于便携式无线应用的小型化方法。所提出的天线由一个独特的梯形贴片、50 Ω 三步微带馈线和阶梯截断接地平面组成。贴片锥形将天线的带宽提高到 2.8-12.5 GHz，部分带宽为 127%，覆盖整个 UWB（3.1-10.6 GHz）。因此，它提供了几乎全向的辐射方向图、更好的增益和出色的辐射效率。馈线的三个步骤增加了贴片的电气长度，实现了制造天线的尺寸减小到 20 mm × 29 mm。一般来说，UWB 系统由于来自未经许可的无线通信设备的强窄带信号干扰而受到影响。为了避免这种情况，所提出的天线被设计成具有四倍带陷特性。它包括三个倒置的 U 型槽（长度接近导波波长的一半），用于抑制 3.5、4.5 和 5.2/5.8 GHz 频段。此外，除了馈线之外，还使用了一对 C 型带来抑制 8.35 GHz X 波段。仿真结果还与样机的实验性能在反射系数、电压驻波比、辐射方向图、传递函数、群延迟和天线增益等方面进行了比较。用于拒绝 3.5、4.5 和 5.2/5.8 GHz 频段。此外，除了馈线之外，还使用了一对 C 型带来抑制 8.35 GHz X 波段。仿真结果还与样机的实验性能在反射系数、电压驻波比、辐射方向图、传递函数、群延迟和天线增益等方面进行了比较。用于拒绝 3.5、4.5 和 5.2/5.8 GHz 频段。此外，除了馈线之外，还使用了一对 C 型带来抑制 8.35 GHz X 波段。仿真结果还与样机的实验性能在反射系数、电压驻波比、辐射方向图、传递函数、群延迟和天线增益等方面进行了比较。