Linearly Polarized Metasurface Inspired Multi-Element Antenna for Aircraft Surveillance Applications

A linearly polarized, compact, dual-band, high gain antenna is proposed for aircraft collision avoidance system (ACAS) or aircraft surveillance applications. The ACAS is an airborne electronic equipment developed to prevent mid-air collisions between two civilian airplanes. A multi-element patch antenna is utilized to address the shortcomings of the conventional ACAS antenna (an array of four monopole antennas) concerning gain (3.6dB), bandwidth, and dimensions ( $\lt \mathrm {1.5}\lambda $ ) when operating at 1.06GHz central frequency. The antenna design consists of four symmetric radiator panels organized in a circular pattern with dimensions of $\mathrm {0.88\times 0.88\times 0.01}\mathrm {\lambda }^{3}\mathrm {(250\times 250\times 3.175}{\mathrm {mm}}^{3})$ . It is fed in sequence to provide complete 360° coverage in the azimuth plane, which is crucial for surveillance purposes. To achieve the dual resonance with the precise band coverage required for the ACAS, significant work on the ground structure has been done by integrating numerous approaches, including an array of metamaterial (MTM), defected ground structure (DGS), and meandering line (ML). Later, an MTM slab ( $6 \times 4$ MTM unit cells) is deployed vertically on all four sides of the antenna to improve overall antenna gain. The effective medium ratio (EMR) of the presented MTM cell is 12.86, which implies the overall size of the MTM cell is $\lt \mathrm {\lambda /12}$ , and it exhibits double negative behavior between 0.9−1.18GHz, making it an extremely compact double negative MTM structure. The proposed design is resonating at 1.03GHz and 1.09GHz with an impedance BW of 8.54% (0.98GHz−1.068GHz), 6.88% (1.07GHz−1.145GHz), and a gain of 9.2dB with a 3dB gain BW of 16.98% (0.96GHz−1.14GHz), respectively. Finally, the proposed MTM and antenna structures are fabricated and measured, and the findings affirm the simulations.