Ultrawideband Tightly Coupled Antenna Based on Composite Dual-Line Feeding

This letter proposes a tightly coupled dipole array based on composite dual-line feeding. A new feeding structure was studied, which effectively reduced the array profile height and manufacturing complexity. Specifically, the feeding structure in the proposed array partially adopts two sets of transmission lines, which provide additional reactance compared to a normal feeding structure, resulting in better impedance matching. The proposed array has a broadside bandwidth of 8.2:1 (0.55 GHz to 4.5 GHz). The array can scan up to 75° in the E-plane and operates in the frequency band from 0.63 GHz to 3.7 GHz (5.8:1 bandwidth). The scanning range of the array in the H-plane can reach 60 °from 0.57 GHz to 3.71 GHz (6.5:1 bandwidth). The proposed antenna has a very low profile, only 0.07λ at the lowest operating frequency. A 10 × 10 array prototype was fabricated and tested. The good agreement between the measurement results and simulation results validates the designs. This antenna features an ultra-wide bandwidth, broad scanning range, and compact structure, making it an ideal candidate for modern wireless systems.