Three-dimensional broadband and high-directivity lens antenna made of metamaterials

Abstract

We present the theoretical modeling and prototype demonstration of a three-dimensional broadband, low-loss, dual-polarization, and high-directivity lens antenna using gradient index (GRIN) metamaterials, which is composed of multi-layer microstrip square-ring arrays. The elements of metamaterials, closed square-ring units of variable sizes, are distributed on the planar substrate to satisfy the radial gradient index function and the axial impedance matching layer configuration of the lens. The gradient-index metamaterials are designed to transform the spherical wave-front into the planar wave-front and to minimize the reflection loss. A prototype lens antenna, which consists of a metal conical horn and the gradient-index lens, are simulated, constructed, and measured. The resemblance of simulation and measurement results shows that the prototype lens antenna maintains low return loss and high directivity on the whole X-band (from 8 GHz to 12 GHz). Compared to the traditional horn antenna, the metamaterial GRIN lens antenna has much superior performance—for instance, the gain increases by 6 dBi at 12 GHz. These results demonstrate the feasibility of such a light weight slab metamaterial lens for broadband and high-directivity antenna applications, such as in radar and communication systems. We have used the lens antennas in the measurements of a three-dimensional invisibility cloak due to the high directivity.

Automatic Design of Broadband Gradient Index Metamaterial Lens for Gain Enhancement of Circularly Polarized Antennas

“…In this case, according to Ref. [24], the radial function n(r) describing the effective refractive index of the GRIN metamaterial lens must satisfy the following expression…”

“…Recently, GRIN metamaterial lenses consisting of resonant metamaterials with a positive index of refraction were designed to transform cylindrical or spherical waves into planar waves, yielding antennas with an increased directivity [16][17][18][19][20][21][22][23][24][25]. In particular a highly-sophisticated broadband, dual-linear-polarized, and high-directivity lens horn antenna using GRIN metamaterials, composed of multi-layer microstrip square-ring arrays, was presented in [24]. However, there are still some open issues left in the recent studies of GRIN metamaterial lenses.…”

TRANSFORMATION OPTICS AND APPLICATIONS IN MICROWAVE FREQUENCIES (Invited Paper)

“…As the measured objects have relatively small sizes, the reflecting and scattering properties cannot be well captured under the illumination of conventional horn antenna in the far-field region. A gradient index metamaterial lens antenna was used as the transmitter, fro which the lens aperture is 98 mm [48]. As the metamaterial antenna can produce a narrow-beam plane wave in the near-field region, it is an excellent candidate to measure the reflecting property of the ground plane with finite size and the scattering property of the bump.…”

Manipulating scattering features by metamaterials

“…Metamaterials have been extensively applied in various EM devices or systems, including the invisibility cloaks [17][18][19][20][21], high-performance antennas [22][23][24], various lens structures [25][26][27][28], fabulous illusion devices [29][30][31], photonic devices [32,33], and many other microwave and terahertz devices and systems [34][35][36]. In this review, however, we mainly focus our attention on the application of metamaterials in manipulating the scattering features of objects.…”