Compact diversity antennas for wireless communications

Traditionally antenna diversity has been thought of in terms of space diversity and associated large antenna separations. Generally, however, antenna diversity can be created using space, pattern, angle and polarization diversity. As such antenna diversity can be formed in several compact configurations that are suitable for mobile communications. In this thesis we introduce two types of compact diversity antennas, namely the Y Patch compact integrated antenna and the Slot Monopole diversity antenna. In essence the designs are single element structures but with two feeds. The significance of the designs are that they can be utilized in compact wireless communication handsets to provide diversity signals. In addition the antenna can also act as a duplexer allowing the receive and transmit signals to be well isolated. The Y Patch antenna design is based on merging two patch antennas together in combination with capacitive loading so that a compact design can be obtained. Justification for the design is provided by considering the mutual coupling using the reaction principle and FDTD simulations. Experimental results are also presented for a design that operates in 2.1-2.2GHz band with over 20dB isolation between the ports and cross correlation being less than 0.01. Hence the antenna is for possible application in forthcoming third generation wireless systems. The Slot Monopole antenna design is based on combining a λ/4 slot and monopole antennas that they have orthogonal polarizations. Experimental results are presented for a design that operates in 2.4GHz ISM band. The slot monopole antenna design can be made to be more compact by using meandering geometry. The experimental design also operates in 2.1-2.2GHz band and there is over 15dB isolation between the ports with cross correlation of less than 0.01 for both designs. Comprehensive results are presented and include radiation patterns, S-parameters and signal correlations between ports so that the diversity performance and isolation characteristics of the antennas can be demonstrated