Third- and Fifth-Order Mode Compression of a Dipole Antenna

This communication proposes a novel tri-mode wideband dipole antenna with mode compression. Tri-mode operation and wide bandwidth (BW) are obtained by compressing the third- and fifth-order modes simultaneously and combining them with the first-order mode. The third-order mode is compressed using an elliptical loop formed by loading two identical semi-elliptical stubs at the current-null points of the third-order mode. The overlap area and size of the loop play a critical role to compress/shift the mode. Two symmetrical pairs of L-shaped stubs loaded at the second current-null points of the fifth-order mode compress the fifth mode. The amount of compression depends on the stubs’ length. The stub width and position affect the impedance matching. The proposed antenna has an operational BW from 2.75 to 7.43 GHz that equals to 91.9% BW. The peak gain and electrical size are 3.8 dBi and
$0.32\lambda _{L}\times 0.14\lambda _{L}$
, respectively. The radiation pattern is omnidirectional over the entire impedance BW. A prototype was developed, and the experiments were performed to validate the design concept and computational results. The experimental results are well within the range of the simulation results.