Reflection Coefficient Research Articles

L-Shaped Coplanar Strip Dipole Antenna Sensor for Adulteration Detection

The present study proposes an L-shaped coplanar strip dipole antenna for sensing the presence of adulterants in liquid food samples. The proposed antenna dimensions are optimized using ANSYS HFSS, and a prototype is fabricated and validated. The sensing region is optimized based on the current distribution and measured reflection coefficients. Adulterant detection is performed by monitoring the variation in the reflection coefficient and resonance frequency of the antenna sensor. To verify the effectiveness of the proposed planar dipole as a sensor, an adulterant, which is hydrogen peroxide, is added to various liquid samples – milk, pineapple juice, and mango juice. The reflection coefficient of the antenna sensor is found to vary with various concentrations of the samples in the study. The sensitivity analysis of the antenna sensor and the repeatability of the results is also analyzed in the work. The experimental analysis assures the use of the proposed antenna as a sensor for the detection of adulterants in liquid food samples.

Integration of a compact multiband antenna with CubeSat systems for efficient remote sensing and space applications

Abstract This study investigates a compact multiband antenna integrated with a CubeSat optical system for remote sensing tasks. The proposed antenna is designed and analyzed using the CST Microwave Studio simulation environment. The results on the antenna performance are found to be quite good. Furthermore, the contribution of the FSS structure is investigated and analyzed by mounting it on a 1U CubeSat chassis made of PEEK material. A distinctive feature of the antenna is its compact design, ease of fabrication, and low cost, which are made possible by the advantages of TPU filaments that can be produced using a 3D printer. The antenna can be mounted on the tip of the nanosatellite together with the camera, providing space for solar panels or other equipment without using additional space in the side areas. Given the limited dimensions of CubeSats, our antenna makes efficient use of the surface. The antenna operates in the S, C, X, Ku, K, and Ka bands and achieves gains of 6.31, 4.08, 9.97, 7.06, 7.12, and 8.22 dBi, respectively; the reflection coefficient is much lower than −10 dB, and the VSWR value is below 1.5. In summary, the microstrip patch antenna system proposed in this work can be used in similar CubeSat remote sensing applications, offering excellent performance, reliability, simplicity, and compact dimensions in the fabrication and deployment system. In the future, we plan to perform fabrication and space environment testing of the proposed antenna, such as vibration, thermal vacuum cycling, and thermal shock.

Unconventional Coastal Structures (Kemit Armor Layer)

ABSTRACTThe growth of the marine sector induces substantial demand to develop new types of coastal structures that have minimal impact on neighboring ecosystems and reduce the environmental footprint. This study aims to introduce and check the efficiency of an innovative armor layer for coastal protection towards fostering sustainable coastal management practices. The proposed truncated cube (named Kemit) design incorporates features such as two hollow opposite elbows, half rings, and incomplete pyramidal shapes to enhance wave absorption and promote marine biodiversity. The proposed armor unit has been investigated physically in the wide wave flume of the Coastal Research Institute Egypt. The armor layer performance was introduced through wave reflection, wave dissipation coefficients, and wave overtopping. Six wave conditions (wave height and wave period) were performed to the armor layer in two states of submergence. A comparative analysis with traditional cube‐armored breakwaters under the same circumstances (wave height, wave period, and water depth) reveals superior performance of the proposed “Kemit” armor layer, exhibiting lower wave reflection coefficients (0.56 to 0.68) and lower overtopping, particularly evident in medium water depths. However, in case of lower water depth, the traditional cubes show better efficiency, lower reflection coefficient (0.46 to 0.68), and higher dissipation (0.74 to 0.89). Moreover, the proposed Kemit armor layer decreased the wave overtopping and run‐up over the breakwater cross‐section due to the Kemit steps and porosity. Furthermore, the adoption of innovative technologies can help policymakers increase the resilience of coastal infrastructure and ecosystems.

Approximation for reflection and transmission at a thin isotropic poroelastic bed between two isotropic elastic half‐spaces

AbstractSeismic responses from a horizontal poroelastic layer provide chances to detect fluids and characterize reservoirs. The poroelastic layer can be considered a thin poroelastic bed if the layer's thickness is less than about one‐eighth of the P‐wave wavelength. Most previous theoretical studies on the reflection and transmission of waves in a model containing a thin poroelastic bed employ fluid or poroelastic medium as the overlying media. Existing approximate formulas of PP‐wave reflection coefficients are given for P‐wave normal‐incidence. Thus, this paper derived the wave reflection and transmission approximate formulas of a thin poroelastic bed between two elastic half‐spaces with P‐wave oblique incident. First, we illustrated the exact reflection and transmission matrix equations for P‐wave incidents based on poroelasticity theory and the boundary conditions. Assuming the poroelastic bed's thickness is far less than wavelengths of S‐ and P‐waves, approximate reflection and transmission formulas are expanded in Taylor series centred at value of the parameter defined as the product of angular frequency, thickness and slowness. Numerical results show that the thinner the poroelastic layer, the closer the approximate reflection and transmission coefficients are to the exact ones. The approximate formulas are valid for small and medium angles. Approximated PP‐wave reflection and transmission coefficients are closer to the exact values than those of the converted waves, which is caused by the fact that P‐wave has a lower slowness than S‐wave.

Approximate recovery of the Sturm–Liouville problem on a half-line from the Weyl function

Abstract The inverse problem of the reconstruction of the Sturm–Liouville problem on a half-line from its Weyl function is considered. Given the Weyl function, we obtain the potential in the Schrödinger equation and the boundary condition at the origin. If the boundary condition is known, this problem is equivalent to the inverse scattering problem of the recovery of the potential, which is zero on a half-line, from a given reflection coefficient. We develop a simple and direct method for solving the inverse problem. The method consists of two steps. First, the Jost solution is computed from the Weyl function, by solving a homogeneous Riemann boundary value problem. Second, a system of linear algebraic equations is constructed for the coefficients of series representations of three solutions of the Schrödinger equation. The potential and the boundary condition are then recovered from the first component of the solution vector of the system. A numerical illustration of the functionality of the method is presented.

A low-SAR four-element antenna for ISM/NR78 band applications

ABSTRACT This article introduces a novel four-port doughnut-shaped coplanar waveguide (CPW) multiple-input multiple-output (MIMO) antenna designed for dual-band operation. Operating within the 2.4–2.5 GHz and 4.4–5 GHz frequency ranges, the antenna boasts a remarkable 10 dB impedance bandwidth. Fabricated on a 55 mm x 55 mm x 1.6 mm FR4 substrate, this antenna achieves impressive isolation of over 20 dB among its elements through orthogonal placement, thereby enhancing key MIMO parameters such as envelope correlation coefficient (ECC), total active reflection coefficient (TARC), channel capacity loss (CCL), diversity gain (DG), and mutual coupling enhancement gain (MEG). Fabrication and measurement procedures validate the antenna’s performance, demonstrating close alignment with simulation results. This validation confirms the antenna’s suitability for deployment across various domains, including Industrial, Scientific, and Medical (ISM) bands and the n78 band for biomedical and 5 G applications. Additionally, specific absorption rate (SAR) calculations support the antenna’s performance, ensuring compliance with regulatory standards for human exposure to electromagnetic fields.

The validity of physical optics for microwave analysis: Accuracy through simplicity

Abstract Traditionally, the optics and microwave communities have been separated not only by the THz band but also by differences in technical knowledge, analytical and computational approaches, design processes, and measurement methodologies. In this contribution, we aim to bridge this divide by leveraging a computational asymptotic technique from optics, known as physical optics, which holds significant potential for the microwave/antenna community. This technique allows for precise microwave calculations for radiation patterns, reflection coefficients, material losses, and mutual coupling between antennas.

An experimental study on snow density observation using reflection coefficients

An experimental study on snow density observation using reflection coefficients

Effect of Fe doping on electronic structure and optical properties of two-dimensional CuI

The effects of different concentrations of Fe doping on the photoelectric properties of two-dimensional (2D) CuI semiconductor are studied based on the first-principles calculation method. The results show that both intrinsic 2D CuI and Fe-doped 2D CuI are direct band gap semiconductors. The total state density and partial wave state density of 2D CuI doped with different concentrations of Fe show that the increase in the number of energy bands at Fermi level is due to the influence of Fe-d and Fe-p orbital contributions after Fe doping, which can improve the conductivity of 2D CuI. With the increase of Fe doping concentration, the peak value of <i>ε</i><sub>1</sub> decreases gradually, and the peak value moves toward the high-energy end near the relatively high energy 3 and 6 eV, and the greater the concentration, the more obvious the shift is. These results indicate that Fe doping can enhance the high temperature resistance of 2D CuI. When a small amount of Fe is doped, the <i>ε</i><sub>2</sub> peak value increases, indicating that the ability of material to absorb electromagnetic waves is enhanced, which can stimulate more conductive electrons, and with the increase of Fe doping concentration, the absorption capability decreases, so the conductivity of 2D CuI is inhibited. The absorption coefficient of intrinsic 2D CuI and Fe-doped 2D CuI indicate that the semiconductor has strong ability to absorb photons in the ultraviolet region. The 2D CuI reflection coefficient of doped Fe atoms increases gradually with the increase of metallic properties of doped elements. This study provides theoretical reference for applying the 2D semiconductor materials and 2D CuI to optoelectronic devices. All the data presented in this paper are openly available at <ext-link ext-link-type="uri" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://doi.org/10.57760/sciencedb.j00213.00060">https://doi.org/10.57760/sciencedb.j00213.00060</ext-link>.

Azimuthal Seismic Inversion for Fractured Reservoirs With Orthorhombic Symmetry Based on a Modified Reflection Coefficient Approximation

Azimuthal Seismic Inversion for Fractured Reservoirs With Orthorhombic Symmetry Based on a Modified Reflection Coefficient Approximation

Wide-area film thickness measurement method of water-lubricated polymer bearing based on ultrasonic reflection coefficient phase

Accurate identification of wide-area film thickness is crucial for detecting lubrication failure in water-lubricated bearings. Ultrasonics is an excellent non-destructive method for measuring thickness. However, due to the heterogeneity and acoustic attenuation of polymer materials, obtaining water film information with high-frequency ultrasonic sensors is challenging. There is a blind area in measurement between the resonance model and the phase matching model under low-frequency probes. Additionally, the significant acoustic impedance difference between friction pairs renders the traditional spring model inapplicable. To address these issues, the first zero-crossing method covering the blind area and the spring model-phase method for the thin films was proposed. The proposed method based on the reflection coefficient phase, in combination with existing methods, can achieve wide-area measurement of film thickness. A calibration platform using a polyetheretherketone and stainless-steel is constructed to validate the accuracy of the method. Film thickness measurement tests are conducted, and the sensitivity of various ultrasonic models is analyzed. The results demonstrate that the mean absolute error is less than 5 μm in the water film ranging from 10 μm to 360 μm. When the film thickness exceeds 30 μm, the mean relative error is less than 5 %, conversely, that is 16.61 %.

A Linear system of reflection coefficients for tomographic imaging of breast cancer

A Linear system of reflection coefficients for tomographic imaging of breast cancer

Investigation of surface roughness induced attenuation of reflected waves using a quasi-Monte Carlo method

Abstract An understanding of the influence of surface roughness on wave scattering and accurate predictions of wave amplitudes are crucial for quantitative ultrasonic nondestructive testing and evaluation. In this work, the effects of surface roughness on the reflection coefficient are investigated using a quasi-Monte Carlo (QMC) method. The wave fields reflected from smooth and rough interfaces with an immersion transducer are modeled using the Rayleigh integral method, and the solutions are efficiently calculated using the QMC method for interfaces constructed using pseudo-random samples. The reflected wave fields are simulated and presented, and the properties of coherent and incoherent waves affected by interface roughness are discussed. The surface roughness induced attenuation of reflected waves is calculated using the ratio of received pressures for waves reflected from rough and smooth interfaces, and the predicted results are compared with those obtained using other recognized methods. It is shown that at low levels of roughness, excellent agreement is obtained between the results from the QMC method and the well-known Kirchhoff approximation, while for high levels of roughness, where the Kirchhoff theory gives pessimistic results, the predicted values agree well with those simulated using a finite element modeling approach, thus verifying the effectiveness of the proposed method.

Simulation of single and double anti-reflective film for solar cell

This work presents the analysis of the Fresnel reflection and transmission coefficients at normal incidence to determine an equation for the reflectivity of single and double thin films that are deposited on the reflective surface of a solar cell. The resulting expressions are simulated in the Matlab software, and it is shown how by having such a thin layer, zero reflection can be achieved at a desired wavelength and the zero reflection bandwidth can increase considerably by having a thin double layer.

Design and Optimization of Reconfigurable Intelligent Surfaces Structures

This research investigates the design and optimization of reconfigurable intelligent surfaces (RIS) structures to enhance simultaneous wireless information and power transfer (SWIPT) in cooperative relay networks. The integration of RIS technology with SWIPT offers promising opportunities to improve the energy efficiency and spectral efficiency of wireless communication systems. In this study, we propose novel RIS deployment strategies and optimization algorithms to maximize the performance of SWIPT-enabled cooperative relay networks. First, we analyze the fundamental principles of RIS-assisted SWIPT and cooperative relay networks, considering the unique characteristics and challenges of each component. We then formulate optimization problems to jointly optimize the placement of RIS elements, relay selection, transmit power allocation, and RIS phase configuration to achieve the desired trade-off between communication reliability, energy efficiency, and spectral efficiency. Furthermore, we develop efficient algorithms for channel estimation, feedback, and coordination among RIS, relays, and destination nodes to adapt to dynamic channel conditions and user requirements. We also investigate the impact of RIS deployment on the energy harvesting performance of SWIPT-enabled relay nodes, considering factors such as RIS reflection coefficients, relay-RIS distance, and incident signal power distribution. Moreover, we address security and privacy considerations in RIS-assisted SWIPT, including potential vulnerabilities, authentication mechanisms, and privacy-preserving communication techniques. Finally, we validate the proposed design and optimization techniques through comprehensive simulations and real-world experiments, considering practical constraints such as hardware implementation, energy harvesting efficiency, and deployment scenarios. Overall, this research contributes to advancing the understanding and practical implementation of RIS technology for SWIPT in cooperative relay networks, offering insights into the design, optimization, and performance evaluation of next-generation wireless communication systems.

A Review on Multi-Geometrical Antenna Reflector

Parabolic antennas are among the most important devices for long-distance communications because of their significant advantages in terms of directivity, gain, and power handling capabilities. Hat feeds are frequently used as feeders for parabolic antennas because they exhibit low levels of cross-polarisation, low sidelobes, and low reflection coefficients. However, hat feeds possess a limited impedance bandwidth (IBW) range of just 30% and are not suitable for use in wideband applications. More work is being done with the objective of increasing the hat feed’s bandwidth capacity. The fundamental structure of a hat feed comprises a hat sub-reflector, circular waveguide, and dielectric material to provide structural support. The hat feeder had a bandwidth capacity of 10% at first. Later, the Chinese hat feed was introduced and used, resulting in a notable enhancement of the bandwidth, with an increase of 18%. The hat feed's geometric structure is redesigned with the help of a generic algorithm optimisation to further enhance the bandwidth, resulting in a 33% improvement.

Performance Comparison of Transparent and Non-Transparent Wineglass-Shaped Antenna at 28 GHz

This paper discussed the performance of a wineglass-shaped antenna fabricated on transparent (indium tin oxide on glass) and non-transparent (Rogers RT6006) substrates. Simulated and measured results of coefficient reflection, VSWR, and radiation patterns are compared and analyzed. Both antennas are well matched at the designed frequency with good reflection coefficient. The non-transparent antenna minimum coefficient reflection is -35.45 dB, and the transparent antenna reached the value of -19.71 dB. The non-transparent antenna has higher gain and exhibits symmetrical radiation. The study demonstrates the feasibility of both transparent and non-transparent wineglass antennas at 28 GHz, with the non-transparent offering higher gain and better impedance matching from a better conductivity compared to the transparent material used.

Non-destructive inspection of interfacial debonding in concrete-filled steel tube bridges

ABSTRACT Concrete-filled steel tube (CFST) structures are widely used in the construction of large-scale structures owing to its exceptional load-bearing capacity. However, inadequate construction quality and improper maintenance may cause debonding defects at the steel-concrete interface. Two non-destructive testing methods, i.e. the ultrasonic phased array (UPA) method and the impact acoustic method, are developed for deboning detection. A combined inspection procedure is proposed to balance the detection accuracy and efficiency, where the impact acoustic method is utilised for a rapid preliminary inspection to pinpoint the suspected debonding areas, while the UPA method is sequentially applied to accurately evaluate the debonding rates in the suspected areas. The impact acoustic method analyzes the time-frequency spectrum from the echo signals using wavelet transform, and calculates the vibration energy ratio for debonding detection. The UPA method applies the total focusing method for image reconstruction, and extracts the reflection coefficient at the steel–concrete interface for debonding evaluation. The laboratory experimental results show that the combined method possesses a high accuracy and accurately delineates the range of the debonding defect while preserving the detection efficiency. Field tests conducted on an arch bridge in Foshan, China, verified the effectiveness of the proposed evaluation method.

Photoreconfigurable Metasurface for Independent Full-Space Control of Terahertz Waves.

We present a novel photoreconfigurable metasurface designed for independent and efficient control of electromagnetic waves with identical incident polarization and frequency across the entire spatial domain. The proposed metasurface features a three-layer architecture: a top layer incorporating a gold circular split ring resonator (CSRR) filled with perovskite material and dual C-shaped perovskite resonators; a middle layer of polyimide dielectric; and a bottom layer comprising a perovskite substrate with an oppositely oriented circular split ring resonator filled with gold. By modulating the intensity of a laser beam, we achieve autonomous manipulation of incident circularly polarized terahertz waves in both transmission and reflection modes. Simulation results demonstrate that the metasurface achieves a cross-polarized transmission coefficient of 0.82 without laser illumination and a co-polarization reflection coefficient of 0.8 under laser illumination. Leveraging the geometric phase principle, adjustments to the rotational orientation of the reverse split ring and dual C-shaped perovskite structures enable independent control of transmission and reflection phases. Furthermore, the proposed metasurface induces a +1 order orbital angular momentum in transmission and +2 order in reflection, facilitating beam deflection through metasurface convolution principles. Imaging using metasurface digital imaging technology showcases patterns "NUIST" in reflection and "LOONG" in transmission, illustrating the metasurface design principles via the proposed metasurface. The proposed metasurface's capability for full-space control and reconfigurability presents promising applications in advanced imaging systems, dynamic beam steering, and tunable terahertz devices, highlighting its potential for future technological advancements.

Design and SAR analysis of DGS based deformed microstrip antenna for ON/OFF body smart wearable IoT applications

Abstract This article presents a defected ground structure (DGS)-based deformed microstrip wearable antenna designed for ON/OFF body smart wearable Internet of Things (IoT) applications. The antenna design has certain features such as lightweight, cost-effectiveness, low profile, and flexibility. Fabricated using a Rogers RT/Duroid 5880 substrate with a thickness of 0.508 mm, the proposed antenna includes a deformed rectangular patch and DGS to enhance impedance matching and radiation performance at 2.45 GHz. The results show a low reflection coefficient of approximately -36 dB and a peak gain of 5.61 dBi at 2.45 GHz in a free-space environment without bending. Additionally, the specific absorption rate (SAR) is measured to be 0.249 W/kg for 1g of tissue and 0.137 W/kg for 10g of tissue when the antenna is placed 0.32λ0 away from the body. The study also indicates that SAR values decrease as the distance between the antenna and the body increases. The antenna prototype has been fabricated and experimentally tested under various ON/OFF body conditions and bending scenarios. The measured results closely align with the simulated data, confirming the antenna suitability for ON/OFF body IoT applications. Noteworthy features of the proposed wearable antenna include its conformability and suitability for body-worn applications, making it an excellent candidate for ON/OFF body smart wearable IoT devices.