scholarly journals Graphene Hypersurface for Manipulation of THz Waves

2020 ◽  
Vol 1009 ◽  
pp. 63-68
Author(s):  
Sasmita Dash ◽  
Christos Liaskos ◽  
Ian F. Akyildiz ◽  
Andreas Pitsillides
Keyword(s):  
Active Control ◽  
Ground Plane ◽  
Perfect Absorption ◽  
Reflection And Transmission ◽  
Phase Gradient ◽  
At Resonance ◽  
Anomalous Reflection ◽  
Unit Cells ◽  
Incident Waves ◽  
Thz Waves

In this work, we investigated graphene hypersurface (HSF) for the manipulation of THz waves. The graphene HSF structure is consists of a periodic array of graphene unit cells deposited on silicon substrate and terminated by a metallic ground plane. The performance of the proposed HSF is numerically analyzed. Electromagnetic parameters of HSF such as permeability, permittivity, and impedance are studied. The proposed graphene HSF has active control over absorption, reflection, and transmission of THz waves. The graphene HSF provides perfect absorption, zero reflection and zero transmission at resonance. Moreover, the graphene HSF structure has the advantage of anomalous reflection and frequency reconfiguration. Incident waves can be reflected in the desired direction, depending on the phase gradient of the HSF and the perfect absorption is maintained at all reconfigurable frequencies upon reconfiguration. The results reveal the effectiveness of the graphene HSF for the manipulation of THz waves.

scholarly journals Low-Cost, Low-Profile Wide-Band Radar Cross Section Reduction Using Dual-Concentric Phase Gradient Modulated Surface

Electronics ◽  
2021 ◽  
Vol 10 (13) ◽  
pp. 1552
Author(s):  
Yousef Azizi ◽  
Mohammad Soleimani ◽  
Seyed Hasan Sedighy ◽  
Ladislau Matekovits
Keyword(s):  
Cross Section ◽  
Low Cost ◽  
Wide Band ◽  
Radar Cross Section ◽  
Phase Gradient ◽  
Full Wave ◽  
Low Profile ◽  
Anomalous Reflection ◽  
Measurement Results ◽  
Unit Cells

Design criteria of low-cost, dual-concentric metasurface possessing wideband phase gradient (PG) are introduced. The radar cross-section reduction (RCSR) is explained by anomalous reflection that characterizes the superficial planar. The geometry consists of two single band RCSR modulated surfaces (MSs) that are triggered in each other. Each MS is built-up of square patch (SP) unit cells configured as a modulation structure to realize PG that causes anomalous reflection and monostatic RCSR behavior. Applying sinusoidal modulation to the sequence of the SP unit cells leads to the formation of PG along the surface and hence the intensity of the reflected wave is reduced for the broadside direction (θr=0∘). The proposed structure fabricated on a 0.8 mm thin FR-4 substrate extends over 249 × 249 mm2. It achieves a wide RCSR bandwidth from 20.9 GHz to 45.7 GHz (i.e., relative bandwidth of 75%) as designed in Dassault Systèmes (CST) Microwave Studio as a full-wave simulator and confirmed by the measurement results.

Diffraction in phase gradient acoustic metagratings: multiple reflection and integer parity design

2021 ◽  
Vol 263 (3) ◽  
pp. 3167-3175
Author(s):  
Mohammad Uzair ◽  
Xiao Li ◽  
Yangyang Fu ◽  
Chen Shen
Keyword(s):  
Acoustic Waves ◽  
High Efficiency ◽  
Periodic Structures ◽  
Dominant Role ◽  
Underlying Mechanism ◽  
Multiple Reflections ◽  
Phase Gradient ◽  
Anomalous Reflection ◽  
Unit Cells ◽  
Diffraction Patterns

Diffraction occurs when acoustic waves are incident on periodic structures such as graded metasurfaces. While numerous interesting diffraction phenomena have been observed and demonstrated, the underlying mechanism of diffraction in these structures is often overlooked. Here we provide a generic explanation of diffraction in phase gradient acoustic metagratings and relate high-order diffractions to multiple reflections in the unit cells. As such, we reveal that the number of unit cells within the metagrating plays a dominant role in determining the diffraction patterns. It is also found that the integer parity of the metagrating leads to anomalous reflection and refraction with high efficiency. The theory is verified by numerical simulations and experiments on planar metagratings and provides a powerful mechanism to manipulate acoustic waves. We further extend the theory to cylindrical waveguides for the control of sound vortices via topological charge in azimuthal metagratings. The relevance of the theory in achieving asymmetric wave control and high absorption is also discussed and verified both numerically and experimentally.

Perfect Absorption by an Array of Lossy Dipoles Located Close to a Ground Plane

2019 ◽  
Vol 67 (9) ◽  
pp. 5991-5996
Author(s):  
Ofer Markish ◽  
Daniel Silverstein ◽  
Yehuda Leviatan
Keyword(s):  
Ground Plane ◽  
Perfect Absorption

Wave Propagation Analysis of an Axially Strained, Rotating Timoshenko Shaft: Part II

1997 ◽  
Author(s):  
Bongsu Kang ◽  
Chin An Tan
Keyword(s):  
Boundary Conditions ◽  
Wave Reflection ◽  
Axial Strain ◽  
Free Vibration Analysis ◽  
Reflection And Transmission ◽  
Transmission Coefficients ◽  
Propagation Analysis ◽  
Geometric Discontinuities ◽  
Bernoulli Models ◽  
Incident Waves

Abstract In this paper, the wave reflection and transmission characteristics of an axially strained, rotating Timoshenko shaft under general support and boundary conditions, and with geometric discontinuities are examined. As a continuation to Part I of this paper (Kang and Tan, 1997), the wave reflection and transmission at point supports with finite translational and rotational constraints are further discussed. The reflection and transmission matrices for incident waves upon general supports and geometric discontinuities are derived. These matrices are combined, with the aid of the transfer matrix method, to provide a concise and systematic approach for the free vibration analysis of multi-span rotating shafts with general boundary conditions. Results on the wave reflection and transmission coefficients are presented for both the Timoshenko and the Euler-Bernoulli models to investigate the effects of the axial strain, shaft rotation speed, shear and rotary inertia.

Wideband Microstrip Patch Antennas with Transverse Electric Modes

2020 ◽  
Vol 35 (8) ◽  
pp. 971-974
Author(s):  
Tanzeela Mitha ◽  
Maria Pour
Keyword(s):  
Transverse Electric ◽  
Ground Plane ◽  
Transverse Magnetic ◽  
Impedance Bandwidth ◽  
Patch Antennas ◽  
Microstrip Patch Antennas ◽  
Microstrip Patch ◽  
Te Mode ◽  
Artificial Magnetic Conductors ◽  
Unit Cells

A wideband microstrip patch antenna, exciting the fundamental transverse electric (TE) mode, is investigated. The excitation of the TE mode is facilitated through replacing both of the patch and ground plane of a conventional microstrip antenna with artificial magnetic conductors (AMC), consisting of unipolar compact photonic bandgap (UC-PBG) unit cells. The AMC patch and the ground plane of this antenna behave as magnetic conductors within the bandgap region of the unit cells. Similar to conventional patch antennas, it is shown that by cutting a U-shaped slot in the AMC patch, wideband characteristics are realized. The antenna shows a 40% impedance bandwidth and operates at the TE10 mode. Moreover, the width of the patch is 1.75 times smaller than its length, reducing the overall size of the antenna by about 60%, compared with the conventional U-slot PEC antenna supporting the transverse magnetic (TM) mode.

scholarly journals A Compact, Low-Profile Log-Periodic Meandered Dipole Array Antenna with an Artificial Magnetic Conductor

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Oh Heon Kwon ◽  
Sungwoo Lee ◽  
Jong Min Lee ◽  
Keum Cheol Hwang
Keyword(s):  
Ground Plane ◽  
Array Antenna ◽  
Main Beam ◽  
Beam Direction ◽  
Magnetic Conductor ◽  
Artificial Magnetic Conductor ◽  
Line Configuration ◽  
Low Profile ◽  
Unit Cells ◽  
Meander Line

A compact and low-profile log-periodic meandered dipole array (LPMDA) antenna with an artificial magnetic conductor (AMC) is proposed. For compactness, a meander line configuration is implemented with dipole elements and optimized using a genetic algorithm (GA) to realize the LPMDA antenna. As a result, a size reduction of approximately 30% is achieved as compared to a conventional log-periodic dipole array antenna. To enhance the gain characteristics, the AMC ground plane configuration is realized with 9 × 9 unit cells for the LPMDA antenna. Two prototypes of the proposed LPMDA antennas with and without an AMC are fabricated and measured to verify its performance. The measured −10 dB reflection ratio bandwidths are 2.56 : 1 (0.85–2.18 GHz) and 2.34 : 1 (0.92–2.16 GHz) for the proposed LPMDA antennas with and without the AMC, respectively. The gain at the main beam direction within the operating frequency bandwidth is significantly improved from 3.94–7.17 dBi to 7.86–10.01 dBi by applying the AMC.

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