Embedded Element Patterns in Combination with Circuit Simulations for Multi-Port Antenna Analysis

Doktorsavhandling, 2009

This thesis is a result from work on two different subjects, electromagnetic simulations of reverberation chambers and a methodology for the analysis of multi-port antennas. The subjects can be linked together by their contribution to knowledge in electromagnetic simulations and characterization of antennas. First part of the work resulted in a Thesis of Licentiate degree 2005 [1] and describes a method of moment code that can be used for analyzing Perfect Electric Conductor (PEC) objects in a reverberation chamber. A major part of that thesis deals with the derivation of an efficient Green’s function of a large (in terms of wavelength) PEC cavity. This is relevant as reverberation chambers always are large and conventional electromagnetic simulations for many different stirrer positions to gather statistical data is in practice impossible. The method presented in [A] and [B] significantly reduces convergence time for the computations for this specific problem and hence made such computations possible. Second part of the work [C] - [K] and also the main part in this thesis are about a methodology for the analysis of multi-port antennas. The methodology is based on embedded elements patterns in combination with circuit simulations and can be used for computation of different multi-port antenna parameters such as total radiated power, efficiency, correlation, diversity gain, capacity, impedance match etc. The use of embedded element patterns is suitable for investigations of different component networks (passive or active) connected to the ports of the multi-port antenna. It is shown that such investigations are very efficient due to the reduced number of necessary full-wave electromagnetic field (EM) simulations; only one full-wave EM simulation per antenna port is needed. The efficient methodology also enables parametric studies and optimizations of different component networks aiming not only for improved matching properties but also for improved values of radiating antenna parameters. The second part of the work can be seen as a prolongation of the first part as the first part contributes to the overall work of improving repeatable antenna measurement techniques, resulting in better characterizations of mobile terminals. Good accuracy in characterizations is needed to make correct decisions on antenna and feeding network designs etc. used in the second part of the work.