Optimal design of multiply fed dipole antennas

The gain of a mulitply fed dipole antenna of length
L
, small radius
a
and arbitrary locations of feed voltages along the antenna is computed using the well-known moment method. An optimization routine is then employed to study the possibility of maximizing the gain in a specified angular direction and minimizing it at other directions for any given number of excitations and antenna length in order to determine the optimum complex values and location of each source. The results are presented in tables and graphs for a wide range of antenna length and number of feeds. It is shown that both the gain and beamwidth are improved by this technique at the expense of appearance of new sidelobes and requirement to design a more complicated feed network. The Fourier series expansion method is extended in order to determine the gain of a multiply fed wire antenna, and the results for the radiation pattern show good agreement with those based on the moment method.