Fig. 4. The current distribution under one-balanced port excitation at 28 GHz.
The simulated and measured results of the proposed antenna for circular polarization application are shown in Fig. 5. Port 1, 2, 3 and 4 are excited with the same amplitude and with phase of 0o, 90o, 180o and 270o. The simulated and measured -10 dB impedance bandwidths are 45.71% (23.2–36 GHz) and 28.57% (23.9–31.9 GHz), respectively. The discrepancy is mainly due to the assembling of the radiator and the power divider. The simulated and measured maximum realized gains are 12.81 dBi at 27.5 GHz and 12.15 dBi at 27 GHz, respectively. The measured 3-dB gain bandwidth is 6.75 GHz from 24.25 to 31 GHz (or 24.11% at 28 GHz), while the simulated 3-dB gain bandwidth is 5 GHz from 24.75 to 29.75 GHz (or 17.9 % at 28 GHz). The simulated and measured 3-dB axial ratio bandwidths are 4.2 GHz from 25.5 to 29.75 GHz (or 15% at 28 GHz) and 4.5 GHz from 26.25 to 30.75 GHz (or 16% at 28 GHz), respectively. The simulated and measured radiation patterns have main beams in the broadside direction with cross-polarization lower than -10 dB. The simultaneous current distributions on the interconnected ME dipole radiator is shown in Fig. 6, which demonstrates that the left-hand circular polarization is realized.