In-Band Scattering Cancellation Techniques for Vivaldi Antenna Array

Vivaldi antenna array is extremely suitable for airborne installed phased array developments because of its wide bandwidth and wide scanning angle. Despite its great potential, the usage of the Vivaldi antenna array is still limited by its 3-D structure, which will probably produce large electromagnetic scattering and destroy the stealth property of the airborne platform. In this work, two techniques are developed to reduce the in-band scattering of Vivaldi antenna arrays. First, a novel Vivaldi antenna element with an inherent low scattering level is proposed based on the extraction of the scattering and radiating currents. Second, a chessboard artificial magnetic conductor (AMC) surface with a 180 degrees reflection phase difference is developed to cancel out the scattering caused by the antenna array. Due to the two techniques, an average of 5-10 dB in-band monostatic scattering reduction is realized, while the radiation performance of the 6-18 GHz Vivaldi phased array with a +/- 60 degrees scanning range in the E-/H-planes is preserved. Finally, the prototypes of the proposed 8 x 8 Vivaldi phased array and a reference array are fabricated and measured to demonstrate the effectiveness of the in-band scattering techniques for both normal and oblique incident waves with HH/VV polarized scattering.