Compact antennas for mimo communications
The newest cellular communication standard, 4G-LTE (Long Term Evolution) provides an all internet protocol (IP)-based solutions to the high data rate required of mobile communication applications. It offers 100 Mbit/s and 1 Gbit/s for low mobility and high mobility applications, respectively. These high data rates are possible mainly due to the use of multiple antennas at both ends of the communication system. Therefore, antenna design for this new cellular standard is of high interest. Due to the size limitations of a hand-held device (typically, 120 mm x 65 mm x 5 mm (L x W x H)) designing antennas has become more challenging. Minimal antenna size, mutual coupling between different antennas, and compliance with radiation restrictions are some of the challenges that influence the design of antennas for this new standard. This work focuses on designing compact antennas to be used in mobile handsets as well as wireless routers such as in the IEEE 802.11n standard. The first attempt was to design a two-port co-located circular patch antenna (CPA) and an annular ring antenna (ARA) that utilizes pattern diversity. The idea behind pattern diversity is to generate two orthogonal radiation patterns associated with each port. To reduce the size of the antenna, ferrite material is used as the substrate material. Even though the use of ferrite material leads to a significant size reduction, the dimensions of those antennas are too large to fit in a cellular mobile handset. Therefore, a spatially separated half-cycle meander structure was investigated. This antenna was designed to fit into a mobile handset using FEKO simulations, and then fabricated and tested. By using the simulated S-parameters and radiation patterns, all of these antennas were investigated for communication theoretic performance parameters such as bit error rate (BER) and capacity.
Thesis (Ph.D.)--Wichita State University, College of Engineering, Dept. of Electrical Engineering and Computer Science