Design and parametric study of multiple element MIMO antennas for WLAN

Tremendous growth has been noticed in wireless communication technologies in recent years. The advent of the 4G systems in future have adopted multiple input multiple output (MIMO) as its key feature. Modern day antennas have been scaled down to fit in the compact hand held wireless communication devices. Due to this trend antenna engineers are compelled to design the antennas which are suitable to fit in the compact chassis of hand held terminals. The requirement of size reduction becomes even stringent in case of MIMO systems. It is more challenging to accommodate multiple antennas within a small perimeter of the congested device. Moreover, the mutual coupling or electrical interference between the multiple element antenna (MEA) deteriorates the potential benefits of MIMO system. In this paper a novel hybrid multiband Koch-meander Fractal antenna has been proposed for the application in the WLAN. The proposed single element antenna (SEA) has been optimized to yield all the bands of IEEE 802.11 a/b/g standard. Further, the authors have transformed the SEA into different MEA configurations i.e., two element antenna, two element antenna with enhanced inter element distance and three element antenna configuration for MIMO/diversity systems. The study on the MEA shows that when the antennas are tightly placed adjacent to each other they suffer from high mutual coupling due to lack of an isolation mechanism. However, the 3-D radiation patterns indicate that the mutual coupling between antennas introduced pattern diversity.