Two-element folded-dipole-driven quasi-Yagi array with low mutual coupling

This paper presents a closely spaced two-element folded-dipole-driven quasi-Yagi array with low mutual coupling between adjacent elements. The antenna utilizes a T-junction power divider as the feeding network with an input impedance of 50 Ω. A microstrip stub is added to the ground plane in the middle of the two elements to improve the mutual coupling characteristics. The folded dipole driver is connected to a 50 Ω microstrip line via a broadband microstrip-to-coplanar stripline transition with a quarter-wavelength radial stub. A mutual coupling of less than -21 dB is exhibited between two folded-dipole-driven quasi-Yagi antennas with a center-to-center spacing of 30 mm (0.55 λ0 at 5.5 GHz). The proposed quasi-Yagi array yields a bandwidth of 4.7-6.5 GHz for the -10 dB reflection coefficient and a gain of 6.6-7.6 dBi within the bandwidth range.