Low Cross-Polarization Ultrawideband Tightly Coupled Balanced Antipodal Dipole Array

An ultrawideband, tightly coupled balanced antipodal dipole array ( TC-BADA) with low cross-polarization characteristic is presented. The proposed array achieves a low cross-polarization level by printing a pair of tightly coupled antipodal dipoles on two substrates to form a balanced radiating structure. The antenna elements are fed by a tapered balun with six pairs of vias placed at the balun edges. A meta-surface-based wideangle impedance matching (MS-WAIM) layer is designed based on the equivalent circuit model and current distribution, which improves the beam scanning ability and reduces the antenna profile simultaneously. The simulated results show that the proposed TC-BADA is able to operate over a 5:1 bandwidth (2.05-10.3 GHz) with active VSWR < {2, 2.8, 3.2} for scanning to {broadside, 45 degrees, 60 degrees}, respectively. The cross-polarization levels remain below -35 and -14 dB for scanning up to 60 degrees in E-plane and 45 degrees in D-plane, respectively. The overall antenna profile of the TC-BADA is only 0.51 lambda(H) at the highest operating frequency. A prototype of 16 x 16 array is fabricated and the central 8 x 8 elements are measured. Good agreement is achieved between the simulated and measured results.