Analytical expression of linear antenna´s characteristics using multipole expansion and Chu´s equivalent circuit

Analytical expression including higher-order modes for a linear dipole antenna is derived with the multipole expansion and Chu´s equivalent circuits. Current distribution on the antenna´s conductor and loss caused by the radiation are consistently combined. Input power at the port is approximated to be guided totally on the conductor up to an effective antenna´s radius, and to propagate in free space beyond the radius. The circuit for the power to propagate in free space is expressed by Chu´s equivalent circuits for all the TM modes. With the derived formulae, numerical estimations of the current distributions and input impedances are shown up to 3^rd-order-mode´s resonant frequency. The numerical data are compared with measured data for the antennas with different line widths, and the data are shown to agree well.