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.