A miniaturized low-profile ultrawideband antipodal Vivaldi antenna (AVA) array loaded with edge techniques is presented to enhance mutual coupling. Originating from a conventional AVA, the edges of the adjacent elements are overlapped with shorted pins loaded to expand the low operating band, suppress the in-band resonance and achieve miniaturization. The edge truncation effect of the E-plane array is subsequently improved by adding auxiliary radiating arms and a shorted strip at the end. Eventually, an 8×8 finite array without any complicated feeding mechanism or transition is constructed to verify the design. The measured operating band of the AVA array is 0.9–12 GHz (13.3:1), and the measured active voltage standing wave ratio (VSWR) is less than 3 when scanning up to ±60° in both the E- and H-planes, implying its wideband and wide-angle scanning capability. Owing to its compact size, ultrawide band, wide-angle scanning and simple feeding structure, the proposed AVA array shows promise for application in large-scale arrays and communication systems.

An antipodal Vivaldi antenna (AVA) with novel symmetric two-layer double-slot structure is proposed. When excited with equiamplitude and opposite phase, the two slots will have the sum vector of their E-field vectors parallel to the antenna's plane, which is uniform to the E-field vector in the slot of a balanced AVA with three-layer structure. Compared with a typical AVA with the same size, the proposed antenna has better impedance characteristics because of the amelioration introduced by the coupling between the two slots, as well as the more symmetric radiation patterns and the remarkably lowered cross-polarization level at the endfire direction. For validating the analysis, an UWB balun based on the double-sided parallel stripline is designed for realizing the excitation, and a sample of the proposed antenna is fabricated. The measured results reveal that the proposed has an operating frequency range from 2.8 to 15 GHz, in which the cross-polarization level is less than -24.8 dB. Besides, the group delay of two face-to-face samples has a variation less than 0.62 ns, which exhibits the ability of the novel structure for transferring pulse signal with high fidelity. The simple two-layer structure, together with the improvement both in impedance and radiation characteristics, makes the proposed antenna much desirable for the UWB applications.