Analytical Models and Equivalent Networks of MED Antennas

This work describes a prospective Magneto-Electric Dipole (MED) antenna for cel-lular network applications in the 700/800/850/900 MHz frequency bands and proposes an equivalent model for the antenna input impedance. The studied antenna comprises a half-wavelength “bat wings”-shaped dipole, an elongated magnetic loop, and a ground reflector. The proposed equivalent model is based on Schelkunoff's theory of biconical antennas and the transmission line theory augmented by radiation resistance corrections. The formulated model allows us to investigate the behavior of MED antennas in a broad frequency range. Schelkunoff's theory is utilized here to qualitatively model the operation of the electric dipole of the MED antenna, while the transmission line theory is employed to model the magnetic loop and the feed. Additionally, the transmission-line- based calculations are corrected to take into account radiation from various antenna parts. The ground reflector effect is modeled by a radiation resistance factor equivalent to the Purcell factor. The proposed antenna design has been verified with full-wave numerical simulations. Overall, the numerical results have demonstrated a good agreement with the predictions of the analytical model. The simulation results confirm that the proposed MED antenna with dimensions of
$1.44\lambda\times 1.44\lambda\times 0.27\lambda$
encompasses a bandwidth of about 60% (650–1200 MHz) for
$S_{11} < -15$
dB and has a stable gain above 11.29 dBi.