Wideband Dual-Polarization Slot Antenna With High Isolation by Using Microstrip Line Balun Feed

A wideband dual-polarization slot antenna with high isolation is proposed in this letter. This double-layer antenna consists of two pairs of parallel microstrip line baluns etched on the top surface of the upper layer and bottom surface of the lower layer, respectively. Four circular radiating units are sequentially set in each center of four circular slots on the middle surface between two layers. The dual-polarization characteristic is achieved by exciting two orthogonal capacitive-coupled circular dipole modes. The proposed antenna is fabricated and tested. The measured results show that relative impedance bandwidths of the two ports are 55.9% (2.40-4.26 GHz) and 52.8% (2.40-4.12 GHz). The port isolation is below -35 dB and the cross-polarization level is below -20 dB across the whole band.