On the Loading Effects of Port-Impedance for Efficient Characteristic Mode Analysis of Large-Scale Cross-Band Arrays

The effects of port impedance on the mode behaviors of large-scale cross-band arrays are investigated and showcased by a ground-backed dipole antenna at 3.5 GHz. It is found that the shorted and matched port loadings give consistent results. The results suggest to short-circuit all the ports in a large-scale array of radiators working in highly-different frequencies, hence simplifying the characteristic mode analysis of such arrays with a significantly reduced number of ports whose port-impedances are often unknown in scattering problems. Additionally, the port-impedance is found to affect both the mode-resonant frequencies and weightings of antennas under plane-wave illumination, suggesting a new method of selective mode manipulation by dispersive port-loading in cross-band antennas and arrays.