Design Of Novel Planar Ultra-wideband Antennas

In recent years, the Ultra-WideBand (UWB) short-range wireless communication has become a hot topic. The UWB technology has a series of characteristics such as high confidentiality and low power, and has broad application prospects in many fields. As a key technology of the UWB systems, analysis and design methods of UWB antenna are with great importance for practice. However, existing Local Area Network communication IEEE 802.11a operats in the frequency rang of 5.15 to 5.825 GHz. In order to avoid UWB communications interfere with its each other, a band stop in the 5GHz band would be required, i.e, the UWB antenna need a band-notch characteristic.The paper briefly introduces the research status and significance of UWB antenna, and illustrates that it is necessary to design a compact UWB antenna firstly. Then the historical development of UWB antennas, the main performance parameters of UWB antennas, the requirements of UWB antennas and the classification of compact planar UWB antennas are summarized systematically. Next the basic theories and design methods of the microstrip antenna are discussed and investigated. Finally, two novel planar ultra-wideband antennas with a band-notch characteristic are presented. The main achievements of this work consist of following aspects:(1) The current various configurations of compact planar UWB antennas including their band-notch characteristics are analyzed and summarized systematically. Also thier advantages and disadvantages are compared.(2) A CPW fed novel planar UWB antenna is presented. The proposed antenna is composed of a metal radiation patch and a tapered arc-shaped ground plane. To achieve ultra wideband, two modifications are introduced on the radiation patch. The first one is to remove a 90-degree fan angle on the two upper corners of the patch. The second modification is to shape the bottom of the patch into an arc. The arc-shaped patch and tapered ground plane make good broadband impedance matching of the antenna possible. Simulation results show that the proposed antenna operates over 3.0 to 22.5GHz for Voltage Standing Wave Ratio (VSWR)<2, and completely covers the frequency band 3.1 to 10.6GHz released by Federal Communications Commission (FCC) for a UWB system.(3) By embedding a U-shaped or C-shaped slot in the radiating patch, a frequency band notch between the bandwidth of 5 to 6GHz for Wireless LAN (WLAN) will be obtained. A detailed parametric study of the slots is presented. Simulation results show that the slot length determines the center frequency of the notch band (the slot length is close to about a one-half wavelength at the center frequency), and the width, shape and position of the slots can influence the notch bandwidth and the center frequency of the notch band.The proposed antennas are simulated by the electromagnetic software Ansoft HFSS 11. The impedance bandwidth, radiation pattern, current distribution and the curve of frequency-gain are simulated respectively. Compared with recently published UWB antenna designs, the proposed antennas have advantages of wide impedance bandwidth, good band-notch characteristic, compact in size and good gain flatness.