scholarly journals Modified Luneburg Lens Based on Metamaterials

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Haibing Chen ◽  
Qiang Cheng ◽  
Aihua Huang ◽  
Junyan Dai ◽  
Huiying Lu ◽  
...  
Keyword(s):  
Plane Waves ◽  
Microwave Frequency ◽  
Refractive Index Profile ◽  
Experimental Characterization ◽  
Index Profile ◽  
Cylindrical Waves ◽  
Unit Cells ◽  
Luneburg Lens ◽  
Luneberg Lens

We present the design, fabrication, and experimental characterization of a modified two-dimensional Luneburg lens based on bulk metamaterials. The lens is composed by a number of concentric layers. By varying the geometric dimensions of unit cells in each layer, the gradient refractive index profile required for the modified Luneburg lens can be achieved. The cylindrical waves generated from a point source at the focus point of the lens could be transformed into plane waves as desired in the microwave frequency. The proposed modified Luneburg lens can realize wide-angle beam scanning when the source moves along the circumferential direction inside the lens. Numerical and experimental results validate the performance of the modified Luneberg lens.

scholarly journals Automatic Characterization of the Refractive Index Profile of Fibers by Interferometry

2002 ◽  
Vol os-11 (1) ◽  
pp. 1558925002OS-01
Author(s):  
Han Seong Kim ◽  
Behnam Pourdeyhimi
Keyword(s):  
Refractive Index ◽  
Interference Fringe ◽  
Axial Direction ◽  
Refractive Index Profile ◽  
Path Difference ◽  
Fringe Field ◽  
Index Profile ◽  
Degree Of Orientation ◽  
Non Destructive

Interferometry provides a non-destructive method for examining the refractive index profile or the radial birefringence distribution within fibers. The key step in the interference data reduction involves the extraction of the refractive index profile along the axial direction of the fiber. The profile is due to the path difference between the fiber and the immersion liquid when a fiber is oriented perpendicular to the fringe field in an interference microscope. The refractive index provides a measure of the degree of optical anisotropy and is indicative of the degree of orientation of the structure. This is of particular interest to nonwovens because in thermally bonded nonwovens, the orientation plays a major role in how well the fibers are bonded and the ultimate properties of the fabric. Despite its long history, however, the interpretation of the interference fringe shift is not precisely defined. Consequently, the data are not reproducible from one laboratory to the next. We outline below an objective and quantitative method for precisely measuring a fiber's refractive index profile from a digitized image of the interference fringe. This new algorithm uses the Fast Fourier Transform (FFT) to remove the inherent noise present in the fiber interferogram and to aid in extracting the profile.

Low-Cost Transmitarray Antenna Designs in V-Band based on Unit-Cells with 1 Bit Phase Resolution

Frequenz ◽  
2019 ◽  
Vol 73 (11-12) ◽  
pp. 355-366
Author(s):  
Martin Frank ◽  
Benedict Scheiner ◽  
Fabian Lurz ◽  
Robert Weigel ◽  
Alexander Koelpin
Keyword(s):  
Low Cost ◽  
Beam Steering ◽  
Experimental Characterization ◽  
Frequency Range ◽  
Steering Angle ◽  
V Band ◽  
Unit Cells ◽  
Linearly Polarized ◽  
Phase Resolution

Abstract This paper presents the design and characterization of linearly polarized low-cost transmitarray antennas with ± 70° azimuth beamforming range in V-band in order to add beam steering functionality to existing radar front ends. The transmitarray antennas are composed of 13 × 13 planar unit-cells. The unit-cells consist of two layers of RO4350B laminate and provide a one bit phase resolution. The desired unit-cell behavior has been validated by simulations and measurements. Eight transmitarrays with different phase distributions have been designed and fabricated to realize different beam steering angles in azimuth. The experimental characterization of the radiation patterns shows the desired performance in the frequency range from 59 GHz to 63 GHz. Additionally, steering angle combinations in azimuth and elevation up to 40° have been realized and successfully demonstrate by measuring the 2D radiation pattern.

scholarly journals Mlines characterization of the refractive index profile of SiGe gradient waveguides at 215 µm

2013 ◽  
Vol 21 (9) ◽  
pp. 11506 ◽  
Author(s):  
Pierre Barritault ◽  
Mickael Brun ◽  
Pierre Labeye ◽  
Olivier Lartigue ◽  
Jean-Michel Hartmann ◽  
...  
Keyword(s):  
Refractive Index ◽  
Refractive Index Profile ◽  
Index Profile

scholarly journals Experimental Characterization of 2 × 2 Electronically Reconfigurable 1 Bit Unit Cells for a Beamforming Transmitarray at X Band

2021 ◽  
Vol 21 (2) ◽  
pp. 153-160
Author(s):  
Biswarup Rana ◽  
In-Gon Lee ◽  
Ic-Pyo Hong
Keyword(s):  
Phase Shifter ◽  
Unit Cell ◽  
Experimental Characterization ◽  
Waveguide Transition ◽  
Transmitted Waves ◽  
X Band ◽  
Unit Cells ◽  
New Type ◽  
Good Agreement

This paper proposes a reconfigurable unit cell for a transmitarray operating at the X band. The unit cell consists of an active patch, a passive patch, and a phase shifter. The active patch has two PIN diodes that change the phase of 180° of the transmitted waves. The passive and active patches both have circular slots to enhance the bandwidth of the transmitted wave. We also propose a new type of experimental characterization technique to measure the performance of the unit cells at the X band without fabricating the entire transmitarray. Instead of a 1 unit cell as described in the literature, we propose 2 × 2 unit cells to measure the performance of unit cells using the X band waveguide. The waveguide consists of a WR-90 section and a rectangular to square waveguide transition section that can be fit to our proposed structure. A good agreement between simulated and measured results was found.

3D refractive index profile for the characterization of necking phenomenon along stretched polypropylene fibres

2010 ◽  
Vol 283 (9) ◽  
pp. 1684-1689 ◽  
Author(s):  
A.A. Hamza ◽  
T.Z.N. Sokkar ◽  
M.A. El-Morsy ◽  
M.I. Raslan ◽  
A.M. Ali
Keyword(s):  
Refractive Index ◽  
Refractive Index Profile ◽  
Index Profile ◽  
Polypropylene Fibres

scholarly journals Direct characterization of the spatial effective refractive index profile in Bragg gratings

2005 ◽  
Vol 17 (12) ◽  
pp. 2685-2687 ◽  
Author(s):  
Zhaowei Zhang ◽  
C. Tian ◽  
M.A.F. Roelens ◽  
M.R. Mokhtar ◽  
P. Petropoulos ◽  
...  
Keyword(s):  
Refractive Index ◽  
Effective Refractive Index ◽  
Bragg Gratings ◽  
Refractive Index Profile ◽  
Index Profile

scholarly journals Hemispherical acoustic Luneburg lens with the acoustic Goos–Hänchen shift and Fresnel filtering effect

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Choon Mahn Park ◽  
Geo-Su Yim ◽  
Kyuman Cho ◽  
Sang Hun Lee
Keyword(s):  
Acoustic Waves ◽  
Total Internal Reflection ◽  
Incident Angle ◽  
Plane Waves ◽  
Homogeneous Medium ◽  
Surface Boundary ◽  
Unit Cells ◽  
Luneburg Lens ◽  
Filtering Effect ◽  
Incident Waves

Abstract A two-dimensional (2D) slice of a 3D hemispherical acoustic Luneburg lens using a quasi-conformal transformation and face-centred-orifice-cubic (FCOC) unit cells is designed and fabricated. With the system, the focusing characteristics of acoustic waves with frequencies that satisfy the homogeneous medium condition of the metamaterial are observed, such as focusing of acoustic plane waves at the antipodal point on the transformed surface of the opposite side for the incident direction and focus spreading due to total internal reflection at the focus point. The attenuation losses of the system are measured and compared with those of an untransformed system with respect to frequency. The value of the acoustic Goos–Hänchen shift is determined by comparing the experimental and theoretical and simulated values of the focus points with respect to the incident angle. The effect of acoustic Fresnel filtering due to the angular distribution of the incident waves at the flat surface boundary is verified by comparing the results of the experiment and a simulation.

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