Design Of UWB Planar Monopole Antennas With Multiple Notched Bands

In recent years, the development of modern wireless communication technologies is very fast. As a key component of modern wireless communication systems, antenna faces more and more challenges. The ultra-wideband (UWB) systems for indoor communications experience a flying growth recently for their merits such as high transmission rate, high capacity and low power consumption. However, there still exist other communication systems over the designated frequency band, such as the wireless local area network (WLAN), which may cause severe electromagnetic interference to the UWB system. Therefore, it is desirable to design UWB antennas with band-notched performance in those frequency bands to avoid potential interference. This thesis mainly focuses on the design of the planar monopole antennas with notched bands for the UWB communication systems.In order to avoid the interferences of WLAN and WiMAX systems to UWB system, a printed planar monopole antenna with dual band-notched characteristic is presented. This antenna with a circular radiator and a ground closing the radiator is fed by a CPW (Coplanar Waveguide). A ring split resonators introduced in the circular patch and a tuning stub in the CPW line are etched to obtain dual notched bands, covering 3.25 to 3.75GHz and 5.1 to 5.75GHz respectively. The entire antenna only occupies a volume of 32mm×40mm×1.5mm, and a good far-field omni-directional radiation in H-plane is provided. Effects of several critical parameters of the antenna on its performance are analyzed by using the HFSS software. Simulated and measured results indicate that the antenna meets the UWB system requirements.An ultra-wideband (UWB) planar monopole antenna with triple band-notched characteristics is proposed. By adding a U-shaped resonant ring on the back side of the antenna, embedding a hexagon-shaped slot on the radiating patch, and employing a U-shape tuning stub introduced in the CPW line, triple notched frequency bands are achieved. Effects of the key parameters on the frequency ranges of the notched bands are also investigated. An antenna prototype is implemented, and the measured results are in good agreement with the simulated results.Finally, some drawbacks of these two antennas are pointed out, and the problems remain to be studied further are given.