Modeling and performance visualization of broadband integrated antennas for radio communications applications

The development of small integrated antennas plays a significant role in the progress of the rapidly expanding military and commercial mobile communications applications. Small efficient antennas that can be used over a wide frequency range are highly desirable. In some cases the antenna can be combined with microelectronic tuning devices to obtain a single multi-function mobile radio system. The characterization of novel antenna designs depends upon the development of simulation tools that can accurately model general perfect conductor wire and surface topologies. This dissertation focuses on the development of broadband integrated communications antennas as well as some associated electromagnetic modeling and performance visualization tools. The characteristics and attributes of various types of antennas for mobile communications are discussed. The surface patch method of moments (MoM) formulation for the simulation and performance evaluation of such antennas is presented. This full-wave analysis method is used to construct a numerical solution of the electric field integral equation to determine the surface currents. The surface patch formulations incorporates vector-valued triangular-domain basis functions with the method of moments. The resulting simulation tools are used to determine the broadband input impedance, radiation patterns, and surface current characteristics for both wire-type and low-profile, integrated antennas. Special attention is given to the creation of accurate input geometry models. This includes conducting detailed convergence and accuracy checks for different antenna configurations. The development and characterization of several new antennas with enhanced bandwidth performance is presented. The new radiators are developed by adding parasitic elements or tuning elements to some well-characterized integrated antennas. The bandwidth is increased while maintaining a low-profile geometry and without internal matching networks. The MoM provides a convenient way to visualize of the currents on the antenna surfaces. This visualization provides insight into the dominant radiation elements of the antenna. The application of an efficient computational technique, (Z) matrix interpolation, into the MoM is discussed. This technique significantly reduces the time it takes to perform MoM antenna simulations at many frequencies. The value of the method is illustrated by its application to a diversity of communications antennas. A detailed study of why the (Z) matrix interpolation method works is presented.