Microstrip Patch Antenna Design with Criss-Cross Metamaterial Based Radome Cover

A high gain microstrip patch antenna with a metamaterial cover over it has been proposed in this paper. A new design namely Criss-Cross metamaterial is being used here. The Criss-Cross unit cell comprises of a cross printed on one face of dielectric substrate and the same cross rotated by 45 - is being printed on the other face of the same substrate. The DNG behavior, i.e., both " and " are simultaneously negative for this metamaterial is obtained at 6GHz; the patch also operates on the same frequency. The radome cover is constructed by stacking three layers made up of a 3 £ 3 Criss-Cross metamaterial array. A 3 £ 3 array of Criss-Cross metamaterial unit cell is printed on Duroid substrate. This arrangement of radome cover increases the gain of a simple patch antenna up to 3.66dB. The radome cover over the antenna is used to protect the structure from environmental hazards. However due to use of conventional dielectric materials as radome, the performance of the antenna degrades. When a metamaterial in printed on such dielectric material, its properties and behavior changes. This leads to improvement of performance of patch antenna along with its physical protection. The directivity of the proposed patch antenna also improves due to the lens behavior of the radome cover over the patch. A conventional radome cover will scatter the EM radiations emitted by the patch antenna. But the metamaterial cover acts as a lens which focuses the EM radiations. This action is once again due to the unusual properties of the metamaterials. 1. INTRODUCTION Patch antenna consists of a patch of metallization on a grounded substrate. These antennas are low-proflle, lightweight and most suitable for aerospace and mobile applications. However, patch antennas also have some limitations such as lower gain, lower e-ciency and narrow bandwidth. There has been a lot of study published on the improvement in the performances of patch antennas. Most of the solutions proposed were to use an array of several antennas. The particular disadvantage of this method comes from the feeding of each antenna and also from the coupling between each element. Other solutions have been suggested to make use of a substrate of either high permittivity or permeability (1). However, this result in big loss of the material and high cost. In the past few years, left-handed metamaterials (LHMs) composed of split-ring resonators (SRRs) and wires have attracted considerable attention because of their unusual electromagnetic properties and can be applied to antennas re∞ectors, fllters, perfect lens and so on (2{4). Burokur etal. (5) numerically studied the in∞uence of LHMs on the performances of the antenna and found the performance of the antenna can be improved using the focusing efiect in the LHMs. Enoch etal. (6) investigated the properties of metallic composite metamaterials and demonstrated that monopol's directivity can be improved greatly using a very low refractive index of metamaterials. Chen etal. (7) theoretically investigated the controllable LHMs based on a varactor-loaded S-shaped resonator structure which can realise continuous scanning capability. In this paper, we study numerically the performances