Abstract
In this paper, two printed multiband fractal monopole antennas using the 1(st) and 2(nd) iteration of Minkowski Island geometry are proposed for WLAN communications. The monopole antennas have compact size of 28 x 18 mm(2) and 21.5 x 18 mm(2), respectively. The proposed antennas with different sizes of the ground plane have also been studied through numerical simulations in Ansoft HFSS. It is found that without using any impedance matching method, both of the proposed antennas exhibit good impedance match at both 2.4 and 5.2 GHz band, which is confirmed by the measurement results. It is also observed that the monopole antenna with the geometry of the 1(st) iteration Minkowslci Island can also operate at 3.5 and 5.8 GHz, which means that it almost covers the entire required frequency bands for 802.11a/b/g and WiMAX communications. The simulation shows that both antennas exhibit high radiation efficiency and the measured radiation patterns show that both antennas have similar radiation patterns at each resonant frequency.

Abstract
This paper proposes a new low profile dual band WLAN Planar inverted-F antenna (PIFA) by using Electromagnetic Band-Gap (EBG) material as ground plane. The total thickness of this antenna is only 4 mm, which is half of the height when a normal perfect electric conductor (PEC) ground plane is used. The backward radiation ratio is also reduced as the existence of EBG. Moreover, the bandwidth for the 5 GHz; band is increased by 10 times compared to the reference antenna. This EBG PIFA is built on the ground plane with size of 40x62 mm, which is suitable for most of the mobile devices.

Abstract

Abstract

Abstract
We report the use of the electric arc technique to apodise Fibre Bragg Gratings (FBG). Electric arc discharges applied at the ends of the grating produce a smoothing of the refractive index modulation profile which reduces the side lobes at longer wavelengths. Using this technique, a FBG was apodised with a side lobe reduction of 17 dB.

Abstract
This work studies dual-band EBG structures used as an Artificial Magnetic Conductor (AMC) ground plane for WLAN co-planar antenna to achieve a low profile structure. From the simulation results, the EBG surface geometry with Jerusalem Cross (JCSS) slot has been chosen in this study. A dual band prototype operating at 2.4 and 5.2 GHz has been implemented and tested. The results show that the EBG antenna can work properly at desired frequency bands with improved gain and reduced back lobe. ©2008 IEEE.