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The fabricated prototype and topology of the proposed antenna. (a) The photograph of the prototype antenna. (b) The cut-open view of the proposed antenna. (c) The cross-section along E-plane of the proposed antenna. The detailed dimensions (unit: mm) are a = 15.8 , b = 7.9 , c = 2.1 , d = 2.7 , e = 3.9 , f = 14.3 , g = 4.85 , h = 3.5 , i = 22 , and t = 2 .
Source publication
A novel wideband waveguide antenna with excellent performance is proposed, which is composed of a coaxial-waveguide transition and an open-ended rectangular waveguide loaded with a pair of horizontal umbrella-shaped metallic brims. The brims perpendicular to two broad walls of the waveguide are constructed to modulate the antenna to radiate nearly...
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We propose in this paper the design, realization and experimental characterization of a low-profile metamaterial "bent" monopole antenna with a total height of 0.027 λ0 and a fractional bandwidth of 24.4% around 1.3 GHz. The metamaterial (MTM) structure is a dual-layer mushroom-like electromagnetic band gap (DL-EBG) conceived and optimized to impro...
Citations
... The metasurfaces are composed of Jerusalem Cross structures and a grounded plane spaced by a dielectric substrate. A Ku-band coax-to-waveguide device is placed in front of the metasurfaces used as the feeding source, which can generate quasi-spherical incident waves with linear polarization 39 . The quasi-spherical incident waves can be reflected by the metasurfaces with high efficiency, while the reflected phases of x-and y-polarized waves can be controlled independently by changing the dimensions of the I-shaped structures on x and y directions, respectively. ...
... If a feeding source is placed in front of the metasurface with v polarization, then the incident waves are v-polarized waves, and the electric-field vector of E v can be decomposed to E x and E y with |E x | = |E y |, so the x-and y-polarized waves can be controlled independently by phase distributions of the metasurface in x and y directions, respectively. We remark that the feeding source used in our simulations and experiments is a linearly polarized Ku-band (12 GHz-18 GHz) coax-to-waveguide device with nearly equal E-and H-plane radiation patterns 39 . In the following, three specific examples are investigated by simulations to show the powerful ability of the proposed anisotropic metasurfaces in multi-beam reflections with independent control of polarizations. ...
We propose a method to convert linearly polarized incident electromagnetic waves fed by a single source into multi-beam reflections with independent control of polarizations based on anisotropic metasurface at microwave frequencies. The metasurface is composed of Jerusalem Cross structures and grounded plane spaced by a dielectric substrate. By designing the reflection-phase distributions of the anisotropic metasurface along the x and y directions, the x- and y-polarized incident waves can be manipulated independently to realize multi-beam reflections. When the x- and y-polarized reflected beams are designed to the same direction with equal amplitude, the polarization state of the beam will be only controlled by the phase difference between the x- and y-polarized reflected waves. Three examples are presented to show the multi-beam reflections with flexible control of polarizations by using anisotropic metasurfaces and excellent performance. Particularly, we designed, fabricated, and measured an anisotropic metasurface for two reflected beams with one linearly polarized and the other circularly polarized. The measurement results have good agreement with the simulations in a broad bandwidth.
... If we make the refraction index to have a special axially-symmetric distribution, a conical wavefront will be directly generated, as illustrated in Fig. 1(a). This Bessel beam launcher includes two parts: one is the planar GRIN metamaterial lens and the other is a feed with axially symmetric radiation patterns 36 . In contrast to the axicon setup which needs Gaussian beams for excitation, the GRIN lens is illuminated by a nearly spherical wave emitted from the feed, a broadband waveguide antenna. ...
... Aditionally, the paraxial approxiamtion is assumed in the design, therefore, the launcher is designed based on the refractive index of the lens without consideration for polarization conversion. The polarization of the beam is based on that of the feed 36 . ...
... The transverse component of electric field distributions at the aperture of the GRIN lens, including amplitude and phase, are depicted in Fig. 3. It can be observed that the distributions are rotationally symmetric, which is guaranteed by the feed with axially symmetric radiation patterns 36 . The symmetric property of the aperture field also guarantees the symmetric property of the beams generated by the lens. ...
An approach of generating broadband Bessel beams is presented. The broadband Bessel beams are produced by a gradient index (GRIN) metamaterial lens illuminated by broadband waveguide antenna. The metamaterial lens is constructed with multi-layered structure and each layer is composed of GRIN metamaterials. The metamaterials are designed as dielectric plates printed with metallic patterns in the center region and drilled by air holes near the edge, which operate in wide band. The metamaterial lens serves as a convertor which transforms the spherical beams emitted from feed into conical beams. The conical beams form quasi-Bessel beams in the near-field region. The aperture diameter of the GRIN lens is much larger than the operating wavelength to guarantee the transformation. In principle, this kind of metamaterial lens can produce Bessel beams at arbitrary distance by designing the refractive-index distribution. To verify the approach, we have designed, fabricated and tested a metamaterial lens. Full-wave simulation and experiment results have proved that the generated Bessel beams can be maintained in distance larger than 1 meter within a ranging from 12 GHz to 18 GHz.
... To implement such aperture distributions, two techniques are proposed. Firstly, a proper feeding horn antenna with identical E-and H-plane radiation patterns is carefully designed since the cylindrical lens is rotationally symmetric [28]. Secondly, a global optimization algorithm, the particle swarm optimization, is adopted to optimize the refractive-index distribution of the lens [29]. ...
... To implement such aperture distributions, two techniques are proposed. Firstly, a proper feeding horn antenna with identical E-and H-plane radiation patterns is carefully designed since the cylindrical lens is rotationally symmetric [28]. Secondly, a global optimization algorithm, the particle swarm optimization, is adopted to optimize the refractive-index distribution of the lens [29]. ...
Metamaterials (MTMs) have advantages to control electromagnetic (EM) waves with high flexibility. However, the application of MTMs in antennas has mainly focused on controlling the phases of EM waves (e.g., to transform spherical waves into planar waves in flat lens and Luneburg lens). In this work, we experimentally demonstrate a method to control the radiation patterns in broadband using MTMs. By controlling the inhomogeneous refractive-index distribution of MTMs, both amplitudes and phases of EM waves on the antenna aperture are designed as required. We present an example to produce a new MTM lens antenna to possess high gain and low sidelobes simultaneously. Experimental results show excellent performance of the antenna in a broad band from 12 GHz to 18 GHz.
We propose a strategy to convert a linearly polarized wave from a single point source to an orbital angular momentum (OAM) wave by arbitrary polarization via an anisotropic frequency selective surface (FSS) in the microwave frequency. By tailoring the geometries of FSS elements, reflection-phases in x and y polarizations are engineered and encoded independently, which allows us to design the eventual polarization state of the generated OAM vortex beam by elaborately selecting individual coding sequences for each polarization. Two types of FSSs are designed and experimentally characterized to demonstrate the capability of OAM generation with circular and linear polarizations, respectively, showing excellent performance in a wide bandwidth from 14 to 16 GHz. This method provides opportunities for polarization multiplexing in microwave OAM communication systems.
A new method is proposed to design gradient refractive-index metamaterial lens antennas by optimizing both the refractive-index distribution of the lens and the feed directivity. Comparing to the conventional design methods, source optimization provides a new degree of freedom to control aperture fields effectively. To demonstrate this method, two lenses with special properties based on this method are designed, to emit high-efficiency plane waves and fan-shaped beams, respectively. Both lenses have good performance and wide frequency band from 12 to 18 GHz, verifying the validity of the proposed method. The plane-wave emitting lens realized a high aperture efficiency of 75%, and the fan-beam lens achieved a high gain of 15 dB over board bandwidth. The experimental results have good agreement with the design targets and full-wave simulations.
