Miniaturization of a wideband magnetoelectric dipole antenna by folding

In this Letter, we investigate a wideband magnetoelectric dipole antenna miniaturized by folding. In the proposed design, a folded L-shaped electric dipole is used instead of the conventional half-wavelength horizontal electric dipole, and a pair of vertically folded shorted patches act as a magnetic dipole, producing a miniaturized radiator. Furthermore, a small-size U-shaped reflector replaces the traditional large-size planar reflector, resulting in a decrease in the low end of the frequency band, while the high end of the frequency band remains almost unchanged. A better impedance matching is also obtained over the entire operating frequency band. Ultimately, a miniaturized overall structure and a wide bandwidth are obtained simultaneously. The overall size of the proposed antenna is only 0 . 25 lambda L x 0 . 25 lambda L x 0 . 12 lambda L ${\boldsymbol{0}}{\boldsymbol{.}}{\boldsymbol{25}}{{\boldsymbol{\lambda }}}_{{\boldsymbol{L}}}{\boldsymbol{\times }}{\boldsymbol{0}}{\boldsymbol{.}}{\boldsymbol{25}}{{\boldsymbol{\lambda }}}_{{\boldsymbol{L}}}{\boldsymbol{\times }}{\boldsymbol{0}}{\boldsymbol{.}}{\boldsymbol{12}}{{\boldsymbol{\lambda }}}_{{\boldsymbol{L}}}$ (where lambda L ${{\boldsymbol{\lambda }}}_{{\boldsymbol{L}}}$ is the longest operating wavelength), which is 82% smaller than the size of the original design, but the proposed antenna can still obtain a large bandwidth of 120% (1-4 GHz) for VSWR < 2. Furthermore, stable radiation patterns are realized with an average gain of 5 dBi within the operating frequency band.