Simulation and experimental results: Microstrip power dividers on Rogers 5880 substrate with thickness of 0.254mm are designed for the measurement of the multi-port interconnected ME dipole antenna array under one balanced port excitation and four port excitation as a circularly polarized antenna. The photograph of the fabricated antenna and the power dividers are shown in Fig. 2. An end-launch connector (Qualwave QELC-KF-3) is used to feed the antenna array.
The simulated and measured results for the multi-port interconnected ME dipole antenna array excited at one balanced port with power divider and for the two-balanced-port excitation are shown in Fig. 3. The -10 dB impedance bandwidths are 12.14% (25.4–28.8 GHz) and 12.8% (24.6-28.2 GHz) for simulated and measured one balanced port excitation, respectively. The simulated -10 dB impedance bandwidths is 48.57% (22.4–36 GHz). It should be mentioned that the simulated isolation between two balanced ports is lower than -15dB which enables the proposed antenna array to support the simultaneous reception of two orthogonal polarizations or transmission in either of these polarizations. For one-balanced-port excitation, the maximum realized gain is 13.52 dBi at 27 GHz for both simulation and measurement, and the measured 3-dB gain bandwidth is 4 GHz from 25.25 to 29.25 GHz (or 14.29% at 28 GHz), while the simulated 3-dB gain bandwidth is 5.25 GHz from 24.75 to 30GHz (or 18.75% at 28 GHz). The co-polarized fields are higher than their cross-polarized counterparts by more than 10 dB both simulation and measurement, which indicates a pure linear polarization. Fig. 4 shows the current distribution when port 1 and port 4 are excited with the same amplitude and with the phase of 0o and 180o. The instantaneous currents are almost in phase on the ME dipole radiators. The elements far away from port 1 and port 4 are excited as well due to the interconnected structure, which leads to a high antenna gain.