Internal multiband antennas for wireless communications terminals

Abstract

Modern personal wireless communication devices are required to support multiple communication standards and high data-rate applications. In order to support multiple communication standards, multiband antennas need to be integrated in these devices. For high data rate applications, MIMO communication techniques, which require multiple antennas on both sides of the wireless channel, have become very attractive for small wireless communications terminals due to the availability of highly integrated circuit technology. In this thesis, new antenna solutions have been offered for next-generation portable communications terminals. Miniaturized multiband antennas supporting various cellular and non-cellular communication standards (GSM, DCS, PCS, UMTS, WiBro, Bluetooth, WiMAX, and WLAN etc.) have been designed based on new bandwidth enhancement and antenna miniaturization techniques. The proposed bandwidth enhancement techniques can be effectively used to design ultra-thin multiband / wideband low-profile antennas for portable communication devices. Ultra-thin multiband antennas investigated in this thesis are based on inverted-F structure without ground plane underneath. Design of a novel compact planar inverted-F antenna (PIFA) covering at least ten wireless standards has been thoroughly investigated through numerical simulations using commercially available EM analysis softwares. The antennas have been evaluated in the presence of human hand, head, and various parts in the mobile device such as battery, LCD, and plastic casing. Since the emerging MIMO communication technology is expected to be part of the personal communications terminals for 4-G systems, design and characterization of MIMO antenna arrays have been given special attention in the later part of the thesis. Multiple antennas at same frequency when implemented in small portable devices exhibit high mutual coupling that significantly affects the radiation efficiency and ultimately capacity performance i...