End-fire antenna array with metamaterial decoupling structures for UAV-borne radar

This paper presents the design and implementation of an X-band, 2D, end-fire antenna array that is suitable for UAV-borne radar applications. The array is synthesized by eight printed Yagi-Uda individual antennas arranged in a 4 x 2 configuration and has a 17dBi gain. Each antenna is fed by a microstrip balun and consists of one driven dipole, one reflector and six directors. Since mutual coupling is detrimental to the performance of phased arrays, metamaterial decoupling structures are utilized to enhance the isolation between them. More specifically, mu-negative meanders are inserted between the elements in the E-plane, while a metasurface of ring resonators isolates the elements in the H-plane. As a result, the inter-element coupling is lower than -30dB. The proposed platform can be easily mounted on unmanned aerial vehicles (UAVs) and is an ideal candidate for UAV-borne radars. Simulations along with measurements verify the effectiveness of our design.