Compact and bandwidth-enhanced circular-polarized dipole antenna for 5G base-station applications

A miniaturized and wideband circular-polarized (CP) dipole antenna with couple-feed has been developed for 5G base-station applications. In this design, two novel L-shaped short stubs working as the couple feed are introduced to excite the orthogonal dipole with the orthogonal phase difference. Therefore, CP radiation is realized on the orthogonally arranged dipoles. In addition, a stub-loaded square-ring dipole is utilized to generate another resonant frequency at low frequency, which broaden the working bandwidth and achieve the miniaturization design. To further expand the impedance and axial ratio bandwidths, four branch lines are adopted in the center of crossed square-loops dipoles. The proposed CP antenna using couple feed was finally fabricated and tested. The simulated and measured impedance bandwidth for |S11| < -10 dB is 65.0% from 1.55 to 3.05 GHz. The measured 3 dB axial ratio bandwidth is 37.5% (1.95-2.85 GHz). The measured results prove that this CP antenna can be applied to wideband base-station applications.