An Octave-Bandwidth Half Maxwell Fish-Eye Lens Antenna Using Three-Dimensional Gradient-Index Fractal Metamaterials

Abstract

The design and performance of a novel octave-bandwidth highly-directive half Maxwell fish-eye (HMFE) lens antenna are presented in superextended C band. The three-dimensional (3D) HMFE lens is implemented by gradient-refractive-index (GRIN) metamaterials and launched by an omnidirectional planar microstrip trapezoid printed monopole from the perspective of high integration, light weight and low profile. A new approach is proposed to design the GRIN metamaterial element in terms of a deep subwavelength feature by incorporating fractal geometry. Numerical and experimental results coincide well, showing that the lens enables a considerable gain enhancement of the monopole near 10 dB across a frequency range of 3 to 7.5 GHz while without significantly affecting the cross-polarization patterns and impedance matching. The near-field free-space measurement is also performed in an octave to afford a physical insight into the high gain, which is attributable to the accurate conversion of quasi-spherical waves to plane waves. Moreover, the truncation and homogenization effects of the lens on the antenna directivity are investigated to illustrate the fundamental mechanisms and afford the design guidelines.Index Terms-Broadband, compact, fractals, gradient-refractive-index metamaterial, half Maxwell fisheye lens.

A novel FDTD/WP-PML/NUFFT algorithm applied to the design of a printed metamaterial enhanced antenna

“…In fact, the metamaterial pattern is applied to physical devices aiming to obtain specific responses, like more gain and bandwidth, tune the microwave device at a certain frequency or just impose a rejection region. Several works in recent years have applied the metamaterial technology in different applications, like antennas [13][14][15][16][17][18][19], lens [20][21][22], among others [23,24]. In [14], a Complementary Split Ring Resonator (CSRR) structure is employed to a UWB antenna in order to provide a rejection characteristic in a desired frequency.…”

“…On the other hand, in [15] metamaterial structures are applied to an UHF antenna and a better gain was obtained, while in [24] periodic structures are applied to the septum of a Gigahertz Transverse Electromagnetic (GETEM) chamber, expecting a shift on the resonance frequencies. In [20] gradientrefractive-index (GRIN) fractal metamaterial elements are proposed as an alternative approach to construct a 3D HMFE lens. The proposed fractal geometry improved the success rate of accurate design affecting the broadband and low-loss properties.…”

A novel design of Fabry-Perot antenna using metamaterial superstrate for gain and bandwidth enhancement

“…There are several recently published works which have used superstrates consist of metamaterial elements, in order to improve the gain [20,21]. In the design of patch section of the microstrip antennas, the metamaterial elements can be used in order to increase the bandwidth of the antenna or create multi-band antennas [22,23] and also for reaching directivity increase it can be used in the superstrate of the microstrip and horn antennas [24,25].…”

“…In the design of patch section of the microstrip antennas, the metamaterial elements can be used in order to increase the bandwidth of the antenna or create multi-band antennas [22,23] and also for reaching directivity increase it can be used in the superstrate of the microstrip and horn antennas [24,25]. Using the metamaterial unit-cell in the superstrate of the microstrip antenna [20,21] leads to a significant increase in the antenna gain which can be achieved by implementing multiple superstrates. The proposed antennas in these papers are wideband and the use of superstrate has led to a decrement in bandwidth of the antenna.…”

“…Figure5 shows the configuration which was used in simulations of the S-shaped unitcell that is printed on the FR4 substrate with thickness of 1.6 mm [20,21]. In order to modify the S-shaped unit-cell according to its design parameters, a parametric study was done and some of the achieved S-parameters results for various design parameters which are listed in Table 3 Table 4.…”