A Broadband Circularly Polarized Aperture-Coupled Magneto-Electric Dipole
Yanhong Xu,
Haoxiang Li,
Weiwei Wang,
Nanyue Li,
Xuhui Fan and
Jianqiang Hou
In this paper, a broadband circularly polarized (CP) magneto-electric (ME) dipole antenna based on microstrip line aperture-coupled feeding structure is proposed. The antenna is fed by the microstrip line, which is utilized to couple the energy to the antenna through the slot etched on the ground plane. Based on a linearly polarized (LP) ME dipole antenna, two centrosymmetric L-shaped strips are loaded to the patches located at the +45° diagonal position and the patches located at the -45° diagonal position are truncated. As a result, the current direction is changed to be parallel to the equivalent magnetic current to radiate CP wave. To improve the axial-ratio (AR) bandwidth of the antenna, the rectangular slot initially etched on the ground plane is modified to an asymmetric cross slot, which can generate a minimum AR point at high frequency. In this way, the AR bandwidth is increased from 32.4% to 51.7%. On this basis, to further extend the AR bandwidth, the metal columns are introduced at both ends of the antenna, and another additional AR minimum point is generated at the low frequency. The measured results indicate that the impedance bandwidth (|S11| ≤ -10 dB) is 57% (2.40-4.33 GHz) and the 3 dB AR bandwidth is 63% (2.39-4.57 GHz). Moreover, the proposed antenna exhibits flat gain and stable unidirectional radiation pattern across the operational frequency region.
