Mahsa Ebrahimpouri

Ultrawideband Metasurface Lenses Based on Off-Shifted Opposite Layers

Metasurfaces have demonstrated to be a low-cost solution for the development of directive antennas at high frequency. One of the opportunities of metasurfaces is the possibility to produce planar lenses. However, these lenses usually present a narrow band of operation. This limitation on bandwidth is more restrictive when the required range of refractive index is high. Here, we present a novel implementation of metasurfaces with low dispersion that can be employed for the design of ultrawideband planar lenses. The implementation consists of two mirrored metasurfaces that are displaced exactly a half unit cell. This displacement produces two effects: It increases the equivalent refractive index of the fundamental mode and flattens its frequency dependence.

Design Guidelines for Gap Waveguide Technology Based on Glide-Symmetric Holey Structures

The behavior of a glide-symmetric holey periodic structure as electromagnetic bandgap is studied in this letter. A number of numerical simulations have been carried out in order to define the importance of each constituent parameter of the unit cell. Our proposed structure finds potential application in antennas and circuits based on gap waveguide technology for the millimeter band. The experimental verifications confirm the effects previously analyzed with the numerical studies.

Bespoke Lenses Based on Quasi-Conformal Transformation Optics Technique

In this paper, a systematic method to design a quasi-optimum lens profile based on quasi-conformal transformation optics technique for a given excitation is presented. This method is applied to a number of conventional antennas, such as an aperture and a log-spiral slot. In all these configurations, an increase of the directivity is observed. Furthermore, using this method, a quasi-optimum graded index lens for a broadband enhanced leaky slot excitation is designed and the results are compared with a hyperhemispherical lens with and without matching layers. Our proposed methodology demonstrates to be able to increase the directivity, to reduce the sidelobes and the cross polarization in a broad bandwidth from 20 to 70 GHz. Due to the continuously changed dielectric constant of the lens profile, reflections are also reduced considerably inside the lens.

Cost-Effective Gap Waveguide Technology Based on Glide-Symmetric Holey EBG Structures

We present a novel electromagnetic bandgap (EBG) structure, which can be used to manufacture low-cost waveguiding structures at high frequencies. The unit cell of the proposed EBG consists of glide-symmetric holes in parallel plate waveguide. Using this unit cell in groove gap waveguide technology has a number of advantages over pin-type EBG at high frequencies, such as acquiring higher accuracy because of larger periodicity as well as an easier and cheaper manufacturing process. The performance of the proposed waveguiding structure is demonstrated using both a straight and a double 90° bent lines through simulation and measurement.

A planar steerable 60 GHz leaky wave antenna with Luneburg lens feed

Metasurfaces have recently attracted the attention of researchers and industry due to its planar profile and low cost of manufacturing. Here, a novel metasurface based on holey unit cells is proposed. This cell exhibits effective refractive mode indexes at 60 GHz and it has been employed to design Luneburg lens antenna. This lens provides a highly directive and steerable beam in the horizontal plane. A leaky wave structure has been attached at the end of the lens to increase the directivity in the vertical plane. The whole structure is planar making this antenna ideal for millimeter wave wireless communications.

Lens antennas using QCTO technique

Quasi Conformal Transformation Optics (QCTO) is employed here to produce 3D gradient-index lenses. These lenses are able to improve radiation properties of conventional antennas, such as gain, side lobe levels and cross polarization.

Planar lenses by tailoring holey waveguides

In recent years there has been an increased demand for directive antennas at high frequencies. There are different solutions to increase the directivity of those antennas such as reflectors, lenses or arrays. Nevertheless, reflectors are bulky, devices at those frequencies. Thus, lenses have become a suitable solution for the new generation of antennas.