Eigenvector analysis of isolated and coupled thin antennas

The boundary-integral method is used to solve for eigenvectors that are discrete representations of the characteristic modes of both single-layer and stacked thin microwave antennas. The performance of high-Q resonant devices is adequately represented near each natural frequency by a single characteristic mode. In the case of stacked structures, it is proposed that, instead of thinking in terms of the natural frequencies of the individual antennas (microstrip patches or cavity-backed slot antennas), performance (impedance and patterns) should be considered in terms of the multiple natural frequencies and corresponding characteristic modes of the coupled system.<>