Latest Articles
Highly Sensitive Temperature Sensing via Photonic Spin Hall Effect
Shuaijie Yuan Jin Yang Yong Wang Yu Chen Xinxing Zhou
In this work, we propose a highly sensitive temperature sensor based on photonic spin Hall effect (PSHE). We find that, by involving the liquid crystal (LC) material, the spin spatial and angular shifts in PSHE are very sensitive to the tiny perturbation of temperature when the incident angle of light beam is near the Brewster and critical angles. Importantly, the phase transition from liquid crystal state to liquid state across the clearing point (CP) will lead to the transition of strong spin-orbit interaction to the weak one. During this process, we reveal that the sensitivity of our designed temperature sensor can reach a giant value with 8.27 cm/K which is one order of magnitude improvement compared with the previous Goos-Hänchen effect-based temperature sensor. This work provides an effective method for precisely determining the position of CP and actively manipulating the spin-orbit interaction.
Highly Sensitive Temperature Sensing via Photonic Spin Hall Effect
Improving the Efficiency of Solar Systems by Tracking the MPP Under Different Test Conditions
Alaa Shakir Mahmood Mustafa Teke
The great technological development, the increase in the number of factories, and the large population growth led to an increase in the demand for the consumption of electric energy that we get from traditional methods (fossil fuels). Moreover, the global shortage in fossil fuel sources and their high costs, the global financial and economic crisis, and the harmful emissions it causes for the environment have made researchers look for electrical energy from alternative and environmentally friendly sources. As a renewable energy, solar energy is considered one of the most important sources of electrical energy today because it is easy to obtain at a low cost. However, this type of energy suffers from low efficiency and is greatly affected by changing weather conditions. To address this problem, several techniques have been proposed by research groups, and MPPT is one of those techniques that has been frequently used in recent years to extract maximum power from solar panels despite the instability in weather conditions. This technique can also generate pulses to control the DC-DC boost converter to provide a certain level of voltage. In this paper, three algorithms, namely Perturbation and Observation (P&O), Fuzzy Logic Controller (FLC), and Particle Swarm Optimization (PSO) are modified and applied in the MPPT technology to control the duty cycle of a DC-DC converter. The photovoltaic system consisting of MPPT technology, solar panels, and a DC-DC boost converter was simulated using MATLAB/Simulink. The performances of the three algorithms were compared to determine the best one that guarantees the highest efficiency under multiple test conditions. The simulation results show that PSO was a better performer than others with (99.32%, 97.02%, and 98.33%, respectively).
Improving the Efficiency of Solar Systems by Tracking the MPP under Different Test Conditions
Theoretical and Numerical Study of Wave Port Boundary Conditions for Lorenz Gauge Potential-Based Finite Element Methods
Thomas E. Roth Colin A. Braun
The development of computational electromagnetics methods using potential-based formulations in the Lorenz gauge have been gaining interest as a way to overcome the persistent challenge of low-frequency breakdowns in traditional field-based formulations. Lorenz gauge potential-based finite element methods (FEM) have begun to be explored, but to date have only considered very simple excitations and boundary conditions. In this work, we present a theoretical and numerical study of how the widely used wave port boundary condition can be incorporated into these Lorenz gauge potential-based FEM solvers. In the course of this, we propose a new potential-based FEM approach for analyzing inhomogeneous waveguides that is in the same gauge as the 3D potential-based methods of interest to aid in verifying theoretical claims. We find that this approach has certain null spaces that are unique to the 2D setting it is formulated within that prevent it from overcoming low-frequency breakdown effects in practical applications. However, this method still is valuable for presenting numerical validation of other theoretical predictions made in this work; particularly, that any wave port boundary condition previously developed for field-based methods can be utilized within a 3D Lorenz gauge potential-based FEM solver.
Theoretical and Numerical Study of Wave Port Boundary Conditions for Lorenz Gauge Potential-based Finite Element Methods
Angular Localization of Radio-Frequency Sources Using a Compact Metamaterial Receive Antenna
Abdelwaheb Ourir Arnaud Tourin Mathias Fink Mohamed Kamoun Julien de Rosny
Radio-frequency source localization becomes a major challenge for many applications such as beam-steering or MIMO communication. This task is commonly carried out by taking advantage of the adjustable radiation patterns of phased arrays to scan an area. Nevertheless, it can be difficult and expensive to implement in some frequency bands of the last generation of communication systems. Here, we propose an alternative based on a single port compact metamaterial antenna. We use a finite periodic array of sub-wavelength (λ/6) resonators for the design of this antenna. A microstrip line is added to excite the resonator array etched on a grounded low-loss substrate and to use it as a planar antenna. In such antenna system, the coupling between sub-wavelength resonators is able to induce a strong dispersion and leads to several complex radiation patterns over a specific narrow frequency band. We implement numerical methods to estimate the direction of a target antenna by taking benefits of the complex frequency signatures. We experimentally demonstrate that a single port sub-wavelength antenna made of a finite array of metamaterial resonators is able to retrieve the direction of a narrow band (3.6% relative bandwidth) emitting target around 5.5 GHz with a maximum precision of 3˚. Such a compact planar system (λ/3, λ/2 and 2λ/3) can be used to substitute the phased array localization technique in order to provide the necessary angular information in many applications such as mm-Wave communication and can be extended to high frequency regimes by using the corresponding resonators.
Angular Localization of Radio-frequency Sources Using a Compact Metamaterial Receive Antenna
PIER Letters
A Miniaturized Band-Stop FSS Based on Pixelated Unitcell
Abedin Karimi Morteza Nadi
As wireless devices become increasingly compact, portable, and accessible anywhere, there is a need to increase isolation between them and reduce frequency interference. The purpose of this paper is to suppress interference by using pixelated patterns on a single layer in a miniaturized unit cell. To miniaturize of unitcell, the surface was pixelated into 50 × 50 pixels with a resolution of 0.2 mm × 0.2 mm. The proposed unitcell occupies a small area of 0.06λ0 × 0.06λ0 at GSM frequency (f = 1.8 GHz). The pixelation of the surface allows the surface current to follow a long path. Therefore, unlike the previous works, the miniaturized structure is obtained using a 1D layer without any vias and lumped elements. A signi ficant advantage of this structure is that it is signi ficantly more miniaturized than the current state-of-the-art unitcells and allows for a wider range of applications. Full-wave simulation and measurement results are in good agreement with each other and show stopband at operation frequency. As a result, both simulation and measurement results show that the proposed structure has a dual-polarized characteristic with good angular stability under a variety of incidence angles.
A Miniaturized Band-stop FSS Based on Pixelated Unitcell