Application of coupled-system analysis to bandwidth enhancement of antennas

Very closely spaced radiators, when properly coupled, can produce significant increases in impedance bandwidth with little, if any, increase in volume. This phenomenon is illustrated by analyzing some simple coupled networks which can serve as approximate models for coupled resonant radiators. Several tools are available that contribute to different aspects of the solution. State-space analysis provides a very general approach that demonstrates the properties held in common by various models and their physical counterparts. However, some intermediate steps are important to the understanding of how the system works. Computer subroutines can be used to perform numerical evaluations of eigenvalues (natural frequencies) and eigenvectors of the system matrix. Microwave computer-aided design routines can be used to assess the effect of parametric variations and to vary the parameters in a systematic way in order to attempt to meet a performance goal.<>