Characteristic Mode Analysis of Planar Dipole Antennas

Planar monopole antennas are popular due to their attractive properties, but their operating mechanisms are still not well understood. Based on image theory, planar monopoles can be analyzed using their dipole counterparts. Here, the bandwidth and radiation pattern of planar dipoles is studied in detail using characteristic mode analysis for different design parameters. The results show that insignificant modes can help to improve the bandwidth without contributing to the radiation property. Moreover, a tradeoff is observed between pattern stability and impedance bandwidth as the dipole width varies. Furthermore, it is found that an offset in the feed point leads to a degradation in both the modal and impedance bandwidths.