Design And Development Of Compact And Highly Isolated Antenna For Wireless Application Using Multiple Input Multiple Output Techniques

Abstract

The placement of single antenna on a single board is not the big issue but the placement of multiple antennas, creates problem of mutual coupling. To resolve this issue, different isolation methods are used in MIMO antenna design, the detail of these isolation techniques, their advantages and disadvantages, mathematical aspect of MIMO antenna parameters has been reviewed and analyzed in initial part of the thesis. The designing of compact single band and multiband MIMO antenna for portable devices is of prime concern of the thesis. In this regards different MIMO antennas have been designed to satisfy the requirement of MIMO antenna design. In the first design, modified circular common element antenna for 2.4 GHz WLAN application is proposed. The structure uses a diagonal parasitic element to improve the isolation among antenna ports. The big challenge in common element MIMO antenna was to maintain the isolation among antenna radiators, which has been successfully achieved by modified circular common element antenna geometry and by the use of diagonal parasitic element. In the second design a modified feeding technique is used along with the combination of T-shaped structure and horizontal parasitic element to control mutual coupling. This modified feed line and isolation structure enhances the impedance matching and reduces the mutual coupling. The proposed octagonal-shaped ring radiator achieved 1.9 GHz bandwidth of wide frequency band in 2.1-4.0 GHz frequency band. In third design, a wideband 2x2 meander-line antenna has been reported to satisfy the requirement of 5.8 GHz application. The fourth MIMO antenna covers four frequency bands and resonates at 2.43/3.83/4.4/5.8 GHz frequencies. The prime advantage of the fourth design is its novel structure and isolation enhancement approach without using any isolation method. This design covers Wi-Fi, Bluetooth, WiMAX and C-Band applications. The various MIMO antennas has been proposed in this research for electronics devices used for human interfaces, applications in Wi-Fi, Bluetooth, WI-Max, S-Band, C-Band, ISM and other WLAN application.