Gain Enhancement of a Miniaturized Broadband Patch Antenna Using a Metamaterial Superstrate for Surveillance Applications in Aircraft

In this work, a compact broadband high directive patch antenna is designed for the Airplane Surveillance Applications or Aircraft Collision Avoidance System (ACAS) application. ACAS, also known as TCAS (Traffic Alert and Collision Avoidance System), is installed in all aircraft to prevent accidents or collisions between aircraft. The ACAS requires a compact, high directive, broadband antenna to increase airspace efficiency, cover a larger surveillance region, effectively scan the provided region, and improve channel capacity. Initially, a novel rectangular patch antenna (RPA) structure with three identical modified S-shape slots and two small notches is proposed to achieve a miniaturized broadband performance in comparison to the conventional ACAS antenna. Later, a planar metamaterial (MTM) layer is used as a superstrate to increase the overall gain of the proposed antenna. The proposed ACAS antenna, as well as other structures such as the MTM unit-cell and MTM slab, are designed and simulated using High Frequency Structure Simulator (HFSS) software. The proposed RPA offers excellent impedance matching throughout the frequency band of 960-1164 MHz (allotted frequency band for radionavigation services) with a unidirectional radiation pattern. In comparison to the conventional RPA, the proposed antenna has a 30.77% smaller size, a 7.67% larger fractional bandwidth, but 1.4 dB decrease in antenna gain. Furthermore, a single layer of MTM slab with $4\times 3$ unit-elements is utilized as a superstrate to augment overall antenna gain by up to 2.71 dB. Hence, the proposed miniaturized, broadband, high gain RPA is well suited for the airplane surveillance applications.