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The idea of exporting dispatchable solar electricity from the North African region to Europe is still the subject of several bilateral meetings, workshops, and conferences, despite doubts and previous failures with the Desertec concept. Given that each North African country has its own privacy policy, energy strategy, and distinct approach to the concept of renewable energy exports, while the potential of renewable energy sources varies from country to country, it would be very helpful to assess the potential and export opportunities of each country. In this respect, this paper focuses on the potential of Algeria. Several key factors that can make Algeria an attractive place to supply Europe with dispatchable solar electricity have been identified and discussed. The factors have been identified from the European perspective and can be used to analyze the potentials of neighboring countries. The barriers that could impede the export of dispatchable solar electricity from Algeria to Europe have also been identified. Based on certain given criteria, the paper provides some scenarios of possible solar electricity import corridors from Algeria to Europe. This work is timely as the Algerian government has expressed interest in exporting its surplus electricity to Europe and is studying an electricity interconnection project with Italy.

Recent advancements in Radio-over-Fiber (RoF) technology have positioned it as a promising solution for high-capacity wireless communications. This paper explores novel applications of RoF systems in enhancing phased array antenna (PAA) performance for multi-channel wireless communication applications through the modulation instability (MI) phenomenon. Utilizing fibers experiencing MI with varying group velocity dispersions ($\beta _{2}$) of −20, −11.3, −3.2, and −2 $\text{ps}^{2}/\text{km}$, the RoF system achieves operational flexibility across distinct central frequencies of 12, 16, 30, and 38 GHz, respectively. This approach represents a significant advancement in wireless communication technology, leveraging MI gain and an MI-based control system architecture to enhance performance across diverse frequency bands. The study investigates the impact of MI on modulation efficiency, presenting experimental results validating the feasibility and effectiveness of the proposed approach. The maximum MI gain by employing a 30 km fiber under MI is 18 dB, experimentally. Further optimization, achieved by increasing the fiber length to 45 km and adjusting nonlinear parameters and input power, demonstrates a remarkable MI gain of 38.1 dB. MI-based true time delay (TTD) techniques also address beam squint challenges, enhancing beamforming capabilities. The findings suggest that integrating MI into RoF systems holds excellent potential for improving wireless communication capabilities with reduced costs and space requirements compared to conventional methods. This research contributes to the growing body of knowledge in the field of RoF systems and offers insights into their practical applications in modern wireless communication networks.

Phased array antenna (PAA) technology is essential for applications requiring high gain and wide bandwidth, such as sensors, medical, and 5G. Achieving such a design, however, is a challenging and intricate process that calls for precise calculations and a combination of findings to alter the phase and amplitude of each unit. Furthermore, coupling effects between these PAA structure elements can only be completed with the use of full-wave electromagnetic simulation tools. Due to recent advances, radio-over-fiber (RoF) technology has been positioned as a possible alternative for high-capacity wireless communications. This paper presents a low-cost, multiband Sub-6 GHz 5G PAA with enhanced gain achieved through integration with a new specialized RoF system design to improve PAA performance by using the phenomenon of modulation instability (MI). Optimizing the antenna’s Defected Ground Structure (DGS) leads to even more improvement. To enable operation across three distinct frequency bands (Sub-6 GHz n78 band (3-3.8 GHz), n79 band (3.8-5 GHz), and n46 band (5-5.5 GHz)), the proposed antenna design features four elliptical patches strategically positioned at the four sides of the ground plane, providing comprehensive 360° coverage in the azimuth plane. Additionally, integrating elliptical slots and upper gaps contributes to improvement. The proposed PAA’s experimentally validated gain values are 5.2 dB, 7.4 dB, and 7.8 dB in the n78, n79, and n46 bands, respectively. For improving the performance of the proposed PAA in RoF systems anomalous fibers ( $n_{2} \neq 0$ and $\beta _{2} \lt 0$ ) are employed to consider the modulation instability (MI) phenomenon, which can lead to the generation of the MI gain on the carrier sideband. The true time delay (TTD) technique controls the beam pattern by adjusting the time delay between adjacent radiation elements. Furthermore, the TTD technique utilizes frequency combs for the proposed 4-element array antenna to apply MI gain to all antenna elements.

In this paper, a compact endfire antenna array with low-profile, small clearance, and wideband operation is proposed for millimeter-wave (mmWave) fifth-generation (5G) mobile terminals. The wideband operation is achieved by exciting two identical bow-tie dipoles inserted on both sides of a multilayer substrate fed by an asymmetric open-end stripline to slotline transition. The antenna performance is significantly improved by introducing a set of vertical metallic vias. The proposed antenna element can achieve 29 % from 24.2 GHz to 32.4 GHz with a peak realized gain that varies from 3.5 dBi to 4.5 dBi. A linear 4-element antenna array is arranged and fabricated to verify the proposed antenna beamforming capabilities. The simulated and measured bandwidth achieves a wide range of 34.4 % (24-34 GHz) to support 26, 28, and 30 GHz 5G mmWave bands with an isolation level better than 20 dB and a peak realized gain over the interested bands ranging from 7.56 to 8.14 dBi. The simulated array scanning angle is ± 68° at 28 GHz within 3-dB gain deterioration. Furthermore, the simulated spherical coverage has met the requirements of 3GPP standards which make the proposed antenna array a promising candidate to be integrated within mmWave 5G mobile devices.

Abstract A multifunctional beam splitting frequency selective surface (FSS) is modeled, analyzed, and tested in transmission and reflection modes. The proposed FSS comprises a C-shaped split-ring resonator designed and fabricated on an ultrathin, flexible polyimide material. When a linearly polarized incident wave interacts with the unit cell of the proposed FSS, half of the wave is reflected, and the other half is transmitted at two frequency bands from 5.8–6.2 GHz and 18.5–22 GHz. Moreover, the proposed FSS is angularly stable upto 40° and also performs simultaneous beam splitting and quarter-wave operation within one of its two bands of operation i.e., from 16.5–18.2 GHz. Such flexible beam splitting FSSs with polarization transformation operation and having angular stability, size miniaturization and multi-band operation is a specialized component having potential to be used for electromagnetic wave manipulation in antenna systems, radar technology, stealth technology, wireless communication, satellite communication, medical imaging, security and surveillance, aerospace and defense, and automotive radar.

Introduction/purpose: Among excellent strategies available to control the torque of asynchronous motors, we distinguish direct torque control. This technique of control allows direct control of magnetic flux and electromagnetic torque without the need to decouple them. Also, direct torque control like each control strategy has some drawbacks, the major drawbacks of this technique being operation at a variable switching frequency and flux and electromagnetic ripples due to the use of hysteresis regulators. It worsens acoustic noise, especially at low speeds, as well as the control performances. Methods: To improve the performance of direct torque control especially at low speeds, the authors propose using fractional order PID in combination with type-2 fuzzy logic controllers to regulate the speed of an induction motor controlled by direct torque control. Results: The results obtained by the proposed regulators show the improvements made to the system. Conclusion: The proposed contribution can exert better control efforts.

Deciphering cellular components and the spatial interaction network of the tumor immune microenvironment (TIME) of solid tumors is pivotal for understanding biologically relevant cross-talks and, ultimately, advancing therapies. Multiplexed tissue imaging provides a powerful tool to elucidate spatial complexity in a holistic manner. We established and cross-validated a comprehensive immunophenotyping panel comprising over 121 markers for multiplexed tissue imaging using MACSima™ imaging cyclic staining (MICS) alongside an end-to-end analysis workflow. Applying this panel and workflow to primary cancer tissues, we characterized tumor heterogeneity, investigated potential therapeutical targets, conducted in-depth profiling of cell types and states, sub-phenotyped T cells within the TIME, and scrutinized cellular neighborhoods of diverse T cell subsets. Our findings highlight the advantage of spatial profiling, revealing immunosuppressive molecular signatures of tumor-associated myeloid cells interacting with neighboring exhausted, PD1high T cells in the TIME of hepatocellular carcinoma (HCC). This study establishes a robust framework for spatial exploration of TIMEs in solid tumors and underscores the potency of multiplexed tissue imaging and ultra-deep cell phenotyping in unraveling clinically relevant tumor components.

In this paper, a 3D conformal meta-lens designed for manipulating electromagnetic beams via height-to-phase control is proposed. The structure consists of a 40 × 20 array of tunable unit cells fabricated using 3D printing, enabling full 360° phase compensation. A novel automatic synthesizing method (ASM) with an integrated optimization process based on genetic algorithm (GA) is adopted here to create the meta-lens. Simulation using CST Microwave Studio and MATLAB reveals the antenna’s beam deflection capability by adjusting phase compensations for each unit cell. Various beam scanning techniques are demonstrated, including single-beam, dual-beam generation, and orbital angular momentum (OAM) beam deflection at different angles of 0°, 10°, 15°, 25°, 30°, and 45°. A 3D-printed prototype of the dual-beam feature has been fabricated and measured for validation purposes, with good agreement between both simulation and measurement results, with small discrepancies due to 3D printing’s low resolution and fabrication errors. This meta-lens shows promise for low-cost, high-gain beam deflection in mm-wave wireless communication systems, especially for sensing applications, with potential for wider 2D beam scanning and independent beam deflection enhancements.

In recent decades, the wide use of deep-learning-based methods has consistently improved the performance of remote sensing images and is widely used for hyperspectral change detection (HCD) tasks. However, most of the existing HCD method is based on the convolutional neural network (CNN), which shows limitations in long-range dependencies and also cannot mine sequence features well. The change detection (CD) performance still has margins for improvement. In this study, inspired by the excellent performance of transformers in computer vision, which has shown a significant ability to model global dependencies to attenuate the loss of long-range information, we built a hybrid spatial–spectral convolutional vision transformer (SSViT) for HCD. Our proposed method combines the merits of CNN and transformer to fulfill effective and efficient HCD. This study focused on highly reliable pseudo sample data generation by a selection scenario. To generate a pseudo sample, we have used different methods: 1) predicting change and no-change areas by using Euclidean distance; 2) thresholding by the Chan–Vese segmentation method for determining change and no-change pixels for intensity maps; 3) sorting of change and no-change pixels; and 4) selection of the minimum value of initial no-change pixels as pseudo change sample data, in addition to choosing the maximum intensity value for change candidate pixels as change sample data. The highly reliable change pixels were selected, and then, pseudo training data were used to train the SSViT model. At last, the change map is generated by training the SSViT network based on pseudo training data. The performance of the SSViT model is evaluated for real-world hyperspectral (HS) datasets with different change land cover types. Furthermore, a new series of HS images is introduced for CD purposes. The results of CD show that the HS images have a high potential for detecting subtle changes. The experimental results demonstrate that the proposed SSViT could outperform the advanced HCD methods.

Communication failures and transmission delays are two major issues associated with Wide-Area Damping Controllers (WADCs). While transmission delays have been extensively studied and various solutions have been proposed, little research has been done on communication failures and most of the proposed methods are based on preventive controls. However, in today’s liberalized electricity markets, preventive controls are no longer acceptable and the trend is to use emergency controls instead. This paper proposes a novel emergency control scheme to counteract the loss of remote signals related to the input and to the output of the WADC (i.e., sensor and actuator failures). The proposed scheme is based on a simple criterion, which overcomes the complexity of the previous methods. Modal analysis and time domain simulations are performed to verify the performance of the proposed method. The simulation results show that the proposed method performs well in handling communication failures and can maintain good damping performance. This research work is particularly important in view of the trend towards the wide-scale adoption of wide-area measurement technologies, while the vulnerability to cyber-attacks is increasing.

Abstract In this paper, a new method to facilitate the design of Printed Ridge Gap Waveguide (PRGW) structures is introduced. One of the main difficulties in designing such structures is related to their simulation process which is really time and energy-consuming. Therefore, a suitable boundary condition is considered to bring about the primary structure without involving the bed of nails or mushroom unit cells. Using this technique, a wideband PRGW 3 dB hybrid double-box coupler is designed to serve in mm-wave frequencies at a center frequency of 30 GHz, which can be deployed for the next generation of mobile communication. The designed coupler provides a wide matching and isolation bandwidth with low output amplitude imbalance, which is unique in comparison with current couplers. The prototype of the proposed coupler is fabricated and measured where the simulation and measurement results show a good agreement indicating the strength of the proposed method in PRGW structure design as well. The measured results show the couplers achieve better than 10-dB return loss and isolation over the frequency range from 25 to 40 GHz (46% BW) with the power-split unbalance and phase error within ± 1 dB and ± 5°, respectively. In addition, square mushrooms are chosen here to satisfy the high impedance surface. Not only do they bring about larger stop bandwidth, but also their configuration facilitates the arrangement of them around the coupler. The proposed design has superb characteristics such as low profile, low loss, and easy integration with microwave circuits and systems that can be suitable for designing mm-wave beamforming networks.

Abstract In this paper, a dual-band implantable rectenna is proposed for recharging and operating biomedical implantable devices at 0.915 and 2.45 GHz. The rectenna system consists of a compact dual-band antenna based on a meandered-resonator as well as efficient dual-band rectifier circuit. Both components (antenna and rectifier) are integrated inside a capsule device to simulate and experimentally validate the rectenna. The antenna occupies lower volume ( $$5 \times 5.25 \times 0.25$$ 5 × 5.25 × 0.25 $$\hbox {mm}^{3}$$ mm 3 ), where compactness is achieved using meandered geometry and a slotted ground plane. It maintains quasi-omnidirectional radiation patterns and peak realized gains of −22.1 dBi (915 MHz) and −19.6 dBi (2.45 GHz); thus, its capability is enhanced to harvest the ambient energy from multiple directions. Moreover, a dual-band rectifier is designed using a dual-branch matching network (an L-matching network and open-circuited stub in each branch) with a radio frequency (RF) to direct current (DC) conversion efficiency of 79.9% for the input power of 1 dBm (lower band: 0.915 GHz) and 72.8% for the input power of 3 dBm (upper band: 2.45 GHz). To validate the concept of the rectenna, the implantable antenna and rectifier are fabricated and attached together inside a capsule device, with the measured results verifying the simulated responses. The proposed rectenna efficiently rectifies two RF signals and effectively superimposes on a single load, thus, providing a distinct advantage compared to single-band rectennas. To the best of the authors’ knowledge, this is the first-ever implantable rectenna to perform dual-band RF signal rectification.

In this paper, a wideband and high gain Fabry Perot Resonator Antenna (FPRA) is proposed. It is based on a synthesized compact single partially reflective surface (PRS) layer acting as a superstrate to a slot-coupled feed antenna, which acts as a radiating source element for the proposed design. The PRS is based on a 2-D printed unit cell, where the lower part is a simple circular ring Frequency Selective Surface (FSS), incorporated with a synthesized FSS unit cell, using an automated system through a VBA based interface established between CST Microwave studio and Matlab, and optimized using a binary genetic algorithm. This new FSS layer acts as the upper part of the proposed PRS layer and provided a positive phase gradient. It almost perfectly resembles that of the optimum PRS over the desired frequency range, with a relatively high reflection magnitude, which makes it a promising superstrate candidate for wideband and high gain FP resonator antennas. The fabricated prototype achieved an important performance in terms of impedance bandwidth with 42%, ranging from 11.32 to 17.35 GHz. In addition, the 3-dB gain bandwidth is 36 % from 11.68 to 16.78 GHz, with a maximum peak gain of 14.72 dB achieved at 16 GHz. Consistent and almost invariant radiation patterns are achieved over the Ku-band frequency band of interest. The experimental and simulated results are in good agreement, justifying the feasibility of the proposed design as a high gain and wideband FP resonator antenna.

Future communication standards have an increasing interest in Millimeter Wave (mm-wave) bands, where wide bandwidth and secured communication can be assured. This trend in communication standards stimulates the research community to provide novel antenna configurations in the mm-wave bands. This article proposes a novel design and analysis of hybrid magneto-electric dielectric-resonator dipole antenna that features an electrically small size with ultra-wideband operation and consistent radiation characteristics in the mm-wave band. The proposed antenna is designed based on the combination of multi-resonances produced by a Magneto-Electric (ME) dipole and stacked Dielectric Resonator Antennas (DRAs). In addition, the proposed antenna is implemented using state-of-the-art Printed Circuit Board (PCB) technology, namely, Printed Ridge Gap Waveguide (PRGW) for low loss and cost-efficiency. The combination between the ME-dipole and stacked DRA is adopted to ensure symmetric radiation characteristics in both E- and H-planes over ultra-wideband operation with a deep matching level. Both DRA and ME-dipole elements are designed and studied separately, where a systematic design procedure is presented to obtain initial design parameters. Proper integration between the radiating elements introduced an electrically small size antenna ( $0.64\,\,\lambda \times 0.48\lambda $ ) covers the full Ka-band (26-40 GHz) with a matching level beyond −20 dB and gain stability of 8± 1 dB. The antenna prototype is fabricated, where a good agreement is shown between both simulated and measured results.

A compact ultra-wideband printed ridge gap waveguide directional couplers for millimeter-wave applications are presented in this paper. A multi-layer coupling technique between two resonant patches is adopted to achieve a wider operating bandwidth with better amplitude and phase balance compared to single-layer technology. For this purpose, a systematic design procedure is deployed to achieve several coupling values in the range of 3–10 dB over a wide frequency bandwidth centered at 30 GHz. A 3-dB hybrid coupler is fabricated and measured, where a bandwidth of 12 GHz (about 38% fractional bandwidth) from 25 GHz to 37 GHz is achieved. In addition, the phase balance is $90^{o}$ ± $5^{o}$ over 38% fractional bandwidth with an amplitude balance of 3.4 ± 0.5 dB over a 26.5% centered at 30 GHz. The proposed couplers with superior characteristics such as compactness, low loss, and low dispersion are considered a good candidate for millimeter-wave applications such as the fifth-generation (5G) wireless communications.

Therapies with weak, non-ionizing electromagnetic fields comprise FDA-approved treatments such as Tumor Treating Fields (TTFields) that are used for adjuvant therapy of glioblastoma. In vitro data and animal models suggest a variety of biological TTFields effects. In particular, effects ranging from direct tumoricidal, radio- or chemotherapy-sensitizing, metastatic spread-inhibiting, up to immunostimulation have been described. Diverse underlying molecular mechanisms, such as dielectrophoresis of cellular compounds during cytokinesis, disturbing the formation of the spindle apparatus during mitosis, and perforating the plasma membrane have been proposed. Little attention, however, has been paid to molecular structures that are predestinated to percept electromagnetic fields—the voltage sensors of voltage-gated ion channels. The present review article briefly summarizes the mode of action of voltage sensing by ion channels. Moreover, it introduces into the perception of ultra-weak electric fields by specific organs of fishes with voltage-gated ion channels as key functional units therein. Finally, this article provides an overview of the published data on modulation of ion channel function by diverse external electromagnetic field protocols. Combined, these data strongly point to a function of voltage-gated ion channels as transducers between electricity and biology and, hence, to voltage-gated ion channels as primary targets of electrotherapy.

Abstract Matching the antenna’s impedance to the RF-front-end of a wireless communications system is challenging as the impedance varies with its surround environment. Autonomously matching the antenna to the RF-front-end is therefore essential to optimize power transfer and thereby maintain the antenna’s radiation efficiency. This paper presents a theoretical technique for automatically tuning an LC impedance matching network that compensates antenna mismatch presented to the RF-front-end. The proposed technique converges to a matching point without the need of complex mathematical modelling of the system comprising of non-linear control elements. Digital circuitry is used to implement the required matching circuit. Reliable convergence is achieved within the tuning range of the LC-network using control-loops that can independently control the LC impedance. An algorithm based on the proposed technique was used to verify its effectiveness with various antenna loads. Mismatch error of the technique is less than 0.2%. The technique enables speedy convergence (

Abstract The paper demonstrates an effective technique to significantly enhance the bandwidth and radiation gain of an otherwise narrowband composite right/left-handed transmission-line (CRLH-TL) antenna using a non-Foster impedance matching circuit (NF-IMC) without affecting the antenna’s stability. This is achieved by using the negative reactance of the NF-IMC to counteract the input capacitance of the antenna. Series capacitance of the CRLH-TL unit-cell is created by etching a dielectric spiral slot inside a rectangular microstrip patch that is grounded through a spiraled microstrip inductance. The overall size of the antenna, including the NF-IMC at its lowest operating frequency is 0.335λ0 × 0.137λ0 × 0.003λ0, where λ0 is the free-space wavelength at 1.4 GHz. The performance of the antenna was verified through actual measurements. The stable bandwidth of the antenna for |S11|≤ − 18 dB is greater than 1 GHz (1.4–2.45 GHz), which is significantly wider than the CRLH-TL antenna without the proposed impedance matching circuit. In addition, with the proposed technique the measured radiation gain and efficiency of the antenna are increased on average by 3.2 dBi and 31.5% over the operating frequency band.

This paper presents a new design for a dual-band double-cylinder dielectric resonator antenna (CDRA) capable of efficient operation in microwave and mm-wave frequencies for 5G applications. The novelty of this design lies in the antenna’s capability to suppress harmonics and higher-order modes, resulting in a significant improvement in antenna performance. Additionally, both resonators are made of dielectric materials with different relative permittivities. The design procedure involves the utilization of a larger cylinder-shaped dielectric resonator (D1), which is fed by a vertically mounted copper microstrip securely attached to its outer surface. An air gap is created at the bottom of (D1), and a smaller CDRA (D2) is inserted inside this gap, with its exit facilitated by a coupling aperture slot etched on the ground plane. Furthermore, a low-pass filter (LPF) is added to the feeding line of D1 to eliminate undesirable harmonics in the mm-wave band. The larger CDRA (D1) with a relative permittivity of 6 resonates at 2.4 GHz, achieving a realized gain of 6.7 dBi. On the other hand, the smaller CDRA (D2) with a relative permittivity of 12 resonates at a frequency of 28 GHz, reaching a realized gain of 15.2 dBi. The dimensions of each dielectric resonator can be independently manipulated to control the two frequency bands. The antenna exhibits excellent isolation between its ports, with scattering parameters (S12) and (S21) falling below −72/−46 dBi at the microwave and mm-wave frequencies, respectively, and not exceeding −35 dBi for the entire frequency band. The experimental results of the proposed antenna’s prototype closely align with the simulated results, validating the design’s effectiveness. Overall, this antenna design is well-suited for 5G applications, offering the advantages of dual-band operation, harmonic suppression, frequency band versatility, and high isolation between ports.

In this article, a miniaturized antenna is proposed for 4G/5G multiple input, multiple output (MIMO) applications for smartphones. The proposed antenna is composed of an inverted L-shaped antenna with decoupled elements to cover 4G (2000–2600 MHz), and a planar inverted-F antenna (PIFA) with a J-slot to cover 5G (3400–3600 MHz and 4800–5000 MHz). Furthermore, to achieve the purposes of miniaturization and decoupling, the structure adopts a feeding stub, shorting stub, and outstanding floor, additionally adding the slot to the PIFA, to generate additional frequency bands. Due to the advantages such as multiband operation, MIMO configuration for 5G communications, high isolation, and a compact structure, the proposed antenna design is attractive for 4G/5G smartphones. The antenna array is printed on an FR4 dielectric board, measuring 140 × 70 × 0.8 mm3, with the 4G antenna located on a top 15 mm-long headroom.

Printed ridge gap waveguide (PRGW) is considered among the state of art guiding technologies due to its low signal distortion and low loss at Millimeter Wave (mmWave) spectrum, which motivates the research community to use this guiding structure as a host technology for various passive microwave and mmWave components. One of the most important passive components used in antenna beam-switching networks is the quadrature hybrid directional coupler providing signal power division with 90° phase shift. A featured design of a broadband and compact PRGW hybrid coupler is propose in this paper. A novel design methodology, based on mode analysis, is introduced to design the objective coupler. The proposed design is suitable for mmWave applications with small electrical dimensions ( $1.2\,\,\lambda _{o} \times 1.2\,\,\lambda _{o}$ ), low loss, and wide bandwidth. The proposed hybrid coupler is fabricated on Roger/RT 6002 substrate material of thickness 0.762 mm. The measured results highlight that the coupler can provide a good return loss with a bandwidth of 26.5% at 30 GHz and isolation beyond 15 dB. The measured phase difference between the coupler output ports is equal $90^\circ \pm ~5^\circ $ through the interested operating bandwidth. A clear agreement between the simulated and the measured results over the assigned operating bandwidth has been illustrated.

In this paper a metamaterial-inspired T-matching network is directly imbedded inside the feedline of a microstrip antenna to realize optimum power transfer between the front-end of an RF wireless transceiver and the antenna. The proposed T-matching network, which is composed of an arrangement of series capacitor, shunt inductor, series capacitor, exhibits left-handed metamaterial characteristics. The matching network is first theoretically modelled to gain insight of its limitations. It was then implemented directly in the 50- $\Omega $ feedline to a standard circular patch antenna, which is an unconventional methodology. The antenna’s performance was verified through measurements. With the proposed technique there is 2.7 dBi improvement in the antenna’s radiation gain and 12% increase in the efficiency at the center frequency, and this is achieved over a significantly wider frequency range by a factor of approximately twenty. Moreover, there is good correlation between the theoretical model, method of moments simulation, and the measurement results.

The manuscript presents the design and characterization of a wideband front-end receiver, based on hollow waveguide technology, for the wireless access point (WAP) applications. The Ka-band receiver is comprised of a low-loss beam-switching antenna network (BSAN) with two-dimensional (2D) scanning property. For demodulation, the receiver uses an efficient six-port network (SPN) that is composed of four 90° hybrid couplers and a 90° phase shifter. To suppress the phase imbalance on the entire band of interest, 27 GHz to 33 GHz, a frequency-independent phase shifter with a minimum phase error is suggested. The SPN receiver is integrated with antenna-in-package in waveguide technology to decrease the insertion losses and noise levels at the first stages. To determine the SPN phase errors, a theoretical and experimental analysis of real-time wireless data transmission utilizing phase-shift keying (PSK) and quadrature amplitude modulated (QAM) signal is conducted. Besides, channel capacity along with beamformer influence on channel performance improvement are determined.

The evolution of substantive laws and forms in different societies is a reflection of criminal thought. Historical studies by law scholars have shown that the political, cultural, religious, and geographical structure of societies has been the main cause of the formation and modification of laws and the style of dealing with crime and justice since its inception. The evolution of justice systems reflects the evolution of human thinking on one of the most important issues in human societies. The presence and role of prosecution authorities in different historical periods has been the focus of different jurisdictions, and accordingly, the laws of the jurisdiction of countries have changed frequently. These changes focus on one's interests, social issues, and sometimes both. Prosecution has long been regarded as one of the key pillars of criminal justice. In this regard, the evolution of the role of the prosecuting authority in different historical periods should be studied and extracted through criminal proceedings. What changes have been made during the prosecution process? On the other hand, what are the differences between the prosecution authorities in the signatory countries that currently have the prosecution system? And what is the cause of those differences? In order to answer the questions raised at the outset, it was necessary to examine specifically and precisely the history of the accusative justice system from the outset of the Sumerian and Babel governments. In this regard, the principles and characteristics of this system were studied in a specialized manner. During different periods and based on various political and social changes, the legal and governmental view of the criminal systems and the status of those involved has greatly changed. Studying the role of the prosecutor assigned to a particular person at different times and in different countries, and therefore using the term prosecuting authority, requires investigating the position of other prosecutors and criminal systems. The role of prosecution authorities in the prosecution phase of the prosecution process has also been specifically explored in the context of the evolution of the two countries, the United Kingdom and the United States, due to their avoidance of disclosure.

A new corner-reflector antenna with a tunable gain based on active frequency selective surfaces (AFSSs) is presented. The proposed design comprises a dipole antenna as a source of the electromagnetic (EM) waves, and three reconfigurable AFSS layers of different size arranged at the same side of the dipole. Each screen consists of two AFSS panels that connected in series and rotated towards the feed to form a V-shaped corner reflector. These AFSS layers are mainly used to control the transmission/ reflection characteristics of the proposed antenna. By applying different combinations for ON/OFF states of diodes, the proposed antenna can adjust its gain value. The antenna performance in terms of reflection coefficient, radiation pattern in the H-plane and gain is analyzed at 5.8 GHz. To validate the concept of the proposed antenna, the prototype of the proposed antenna is fabricated and measured. The measured results show a good agreement with the simulated ones.

In this paper, a magneto-electric (ME) dipole antenna excited by two slots through a printed ridge gap waveguide (PRGW) is presented. This antenna, which operates in the Ka-band, is considered as a dual complementary source (DCS), and exhibits a higher gain and a wider impedance bandwidth, compared to conventional ME dipoles. The proposed antenna has an impedance matching bandwidth with |S11| 3 (at 30 GHz) and exhibits a measured impedance bandwidth in excess of 50%, from 24 to 40 GHz, a maximum measured gain of 14.2 dBi at 35 GHz, and a measured radiation efficiency of 93% at 30 GHz.

This paper presents a study of a planar antenna-array inspired by the metamaterial concept where the resonant elements have sub-wavelength dimensions for application in microwave medical imaging systems for detecting tumors in biological tissues. The proposed antenna consists of square-shaped concentric-rings which are connected to a central patch through a common feedline. The array structure comprises several antennas that are arranged to surround the sample breast model. One antenna at a time in the array is used in transmission-mode while others are in receive-mode. The antenna array operates over 2-12 GHz amply covering the frequency range of existing microwave imaging systems. Measured results show that compared to a standard patch antenna array the proposed array with identical dimensions exhibits an average radiation gain and efficiency improvement of 4.8 dBi and 18%, respectively. The average reflection-coefficient of the array over its operating range is better than S11 ≤ -20 dB making it highly receptive to weak signals and minimizing the distortion encountered with the transmission of short duration pulse-trains. Moreover, the proposed antenna-array exhibits high-isolation on average of 30 dB between radiators. This means that antennas in the array (i) can be closely spaced to accommodate more radiators to achieve higher-resolution imaging scans, and (ii) the imagining scans can be done over a wider frequency range to ascertain better contrast in electrical parameters between malignant tumor-tissue and the surrounding normal breast-tissue to facilitate the detection of breast-tumor. It is found that short wavelength gives better resolution. In this experimental study a standard biomedical breast model that mimics a real-human breast in terms of dielectric and optical properties was used to demonstrate the viability of the proposed antenna over a standard patch antenna in the detection and the localization of tumor. These results are encouraging for clinical trials and further refinement of the antenna-array.

In this review paper, a comprehensive study on the concept, theory, and applications of composite right/left-handed transmission lines (CRLH-TLs) by considering their use in antenna system designs have been provided. It is shown that CRLH-TLs with negative permittivity (ε L), shunt LH inductances (LL), series right-handed (RH) inductances (LR), and shunt RH capacitances (CR) that are realized by slots or interdigital capacitors, stubs or via-holes, unwanted current flowing on the surface, and gap distance between the surface and ground-plane, respectively. In the most cases, it is also shown that structures based on CRLH metamaterial-TLs are superior than their conventional alternatives, since they have smaller dimensions, lower-profile, wider bandwidth, better radiation patterns, higher gain and efficiency, which make them easier and more cost-effective to manufacture and mass produce. Hence, a broad range of metamaterial-based design possibilities are introduced to highlight the improvement of the performance parameters that are rare and not often discussed in available literature. Therefore, this survey provides a wide overview of key early-stage concepts of metematerial-based designs as a thorough reference for specialist antennas and microwave circuits designers. To analyze the critical features of metamaterial theory and concept, several examples are used. Comparisons on the basis of physical size, bandwidth, materials, gain, efficiency, and radiation patterns are made for all the examples that are based on CRLH metamaterialTLs. As revealed in all the metematerial design examples, foot-print area decrement is an important issue of study that have a strong impact for the enlargement of the next generation wireless communication systems.

Generative adversarial networks (GANs) have shown striking performances in computer vision applications to augment virtual training samples (VTS). However, the VTS generating by GANs in the context of hyperspectral image classification suffer from structural inconsistency due to the insufficient number of training samples in order to learn high-order features from the discriminator. This work addresses the scarcity of training samples by designing a GAN, in which the performance of discriminator is improved to produce more structurally coherent VTS. In the proposed method, by splitting the discriminator into two parts, GAN undertakes two tasks: the main task is to learn to distinguish between real and fake samples, and the auxiliary task is to learn to distinguish structurally corrupted and real samples. With this setup, GAN will produce real-like VTS with a higher variation than conventional GAN. Furthermore, in order to reduce the computational cost, subspace-based dimension reduction was performed to obtain the dominant features around the training samples to generate meaningful patterns from the original ones to be used in the learning phase. Based on the experimental results on real, and well-known hyperspectral benchmark images, the proposed method improves the performance compared with GANs-related, and conventional data augmentation strategies1.

In this paper, an ultra-wideband and polarization-insensitive frequency-selective surface absorber is presented with oblique incident stable behavior. Different from conventional absorbers, the absorption behavior is much less deteriorated with the increase in the incidence angle. Two hybrid resonators, which are realized by symmetrical graphene patterns, are employed to obtain the desired broadband and polarization-insensitive absorption performance. The optimal impedance-matching behavior is designed at the oblique incidence of electromagnetic waves, and an equivalent circuit model is used to analyze and facilitate the mechanism of the proposed absorber. The results indicate that the absorber can maintain a stable absorption performance with a fractional bandwidth (FWB) of 136.4% up to 40°. With these performances, the proposed UWB absorber could be more competitive in aerospace applications.

Antennas that generate orbital angular momentum (OAM) have the potential to significantly enhance the channel capacity of upcoming wireless systems. This is because different OAM modes that are excited from a shared aperture are orthogonal, which means that each mode can carry a distinct stream of data. As a result, it is possible to transmit multiple data streams at the same time and frequency using a single OAM antenna system. To achieve this, there is a need to develop antennas that can create several OAM modes. This study employs an ultrathin dual-polarized Huygens’ metasurface to design a transmit array (TA) that can generate mixed-OAM modes. Two concentrically-embedded TAs are used to excite the desired modes by achieving the required phase difference according to the coordinate position of each unit cell. The prototype of the TA, which operates at 28 GHz and has a size of 11 × 11 cm 2, generates mixed OAM modes of −1 and −2 using dual-band Huygens’ metasurfaces. To the best of the authors’ knowledge, this is the first time that such a low-profile and dual-polarized OAM carrying mixed vortex beams has been designed using TAs. The maximum gain of the structure is 16 dBi.

We aimed to evaluate the impact of Virtual Reality Dental Simulators (VRDS) on preclinical training in endodontics for undergraduate dental students. Purposive sampling technique was used to target undergraduate dental students at two dental schools: in Qatar and Turkey. After training on endodontic access cavity preparation on upper anterior teeth using acrylic teeth on dental mannequins and virtual reality haptic dental simulator, a questionnaire based on a combination of open- and closed-ended items was distributed to the participants. The sample included 60 dental undergraduate students. The participants reported positive experiences with VRDS and 76% considered it to be helpful in improving their fine motor skills. Endodontic access cavity preparation on VRDS was perceived to be similar to natural and acrylic teeth by 73.34% and 53% of participants, respectively. Overall, 85% of participants supported the use of VRDS training to supplement conventional training on dental mannequins but also recommended the need for improvements in VRDS training in endodontics. The findings of this study underscore the benefits of VRDS in endodontics. Future research involving larger samples from multiple institutions may help to optimize VRDS in undergraduate dental education.

In this paper, a wideband and high-gain circular polarised Fabry–Perot Resonator Antenna (FPRA) with a single partially reflective surface (PRS) layer is automatically generated and optimised using a VBA-based interface system between CST Microwave studio and Matlab. The proposed PRS layer is a promising superstrate for wideband and high-gain FP resonator antennas due to its relatively high reflection coefficient magnitude and positive phase gradient, which resemble that of the optimum PRS over the relevant frequency band. The circular polarisation was achieved using a sequential feeding network for a 2 × 2 array air-gapped slot-coupled elliptical patch antenna. The proposed design achieved an impedance bandwidth of 48.58% (15.3 GHz) ranging from 23.84 GHz to 39.14 GHz, and the −3 dB gain bandwidth was 22.42% (6.25 GHz) from 24.75 to 31 GHz, with a peak gain of 17.12 dB at 29 GHz, and an axial ratio bandwidth of 21.75% (6.2 GHz). In addition, the achieved radiation efficiency was 90%. Consistent and almost invariant radiation patterns are achieved over the millimetre-wave frequency band of interest. The experimental and simulated results are in good agreement, justifying the feasibility of the proposed design as a high-gain and wideband FP resonator array antenna for Mm-wave applications.

Securing energy supply and speeding up the transition towards a reliable, sustainable, low-carbon energy system are among the major current and future challenges facing Europe. Importing dispatchable solar electricity from North Africa is considered as a potential and attractive option. Nevertheless, as things currently stand, the European Commission focuses mainly on the exploitation of the existing wind power potential in the North Sea, largely ignoring the solar power potential in the Sahara region of North Africa. After discussing the major challenges and issues facing Europe to achieve the assigned ambitious objectives, the paper emphasises the importance of North Africa's solar resources in helping Europe to successfully address the challenge of decarbonising its electricity system, in particular with regards to the security of supply and sustainability. Within these two major challenges, the paper explores the issues of access, barriers and opportunities. The paper highlights why the EU's energy and climate goals will not be achievable without adequate grid expansion and grid-scale energy storage facilities, as well as other innovative measures to manage demand and ensure a secure energy supply. In this respect, the paper shows how the import of dispatchable electricity from North Africa via specific HVDC links could play a key role in helping the EU achieve its energy targets in a cost-effective way without recourse to significant investments in transmission infrastructure and storage facilities. The paper then attempts to identify and analyze the main barriers that continue to inhibit the export of solar electricity from North Africa to Europe. Finally, to make the project more attractive and achievable in the near future, the paper proposes a systematic approach for setting up energy import scenarios. A promising import scenario is presented where energy import via Italy is shown to be a more viable and effective solution than via Spain. Keywords: Renewable energy, Sustainable energy development, European supergrid, CSP-HVDC, Desertec

This paper proposes a novel circularly polarized electromagnetic band-gap (EBG) antenna array backed by an artificial magnetic conductor (AMC) that operates in the 26-32-GHz bands. The designed antenna is a 2 x 2 Yagi-Uda antenna array that uses the directors' semicircles to direct the radiation in the horizontal end-fire direction. The feeding of the array is designed with two parallel T-junction portions forming a parallel feeding network that converts the polarization from linear to circular. An AMC is placed underneath the antenna to suppress the backward radiation and obtain the propagation only in the +z plane. The novel approach is based on the fact that EBGs are placed around the array to give to the antenna, beamswitching capability. This simple technique provides a high beam tilting angle of +90° from the end-fire to the full broadside plane. The final EBG-AMC-antenna array is circularly polarized and presents, at 29 GHz, a gain of 11.9 dBi, and an axial ratio bandwidth of 10% from 28 to 31 GHz. By assessing the high antenna performances presented in this paper, and the high angle beam-switching capability by adding the EBG, the novel array could be seen as a potential candidate for implementation in future 5G applications.

A novel millimeter-wave (MMW) hybrid isolator is presented to reduce the mutual-coupling (MC) between two closely-spaced dielectric resonators (DR) antennas at 60 GHz. The proposed hybrid isolator consists of a combination of a new uni-planar compact electromagnetic band-gap (EBG) structure and an MMW choke absorber. The design of the proposed EBG unit-cell is based on the stepped-impedance resonator (SIR) technique. The results show that the proposed EBG structure provides a wide frequency bandgap in the 60 GHz band with miniaturization factors of 0.79 and 0.66 compared to conventional uni-planar EBG and uni-planar compact (UC-EBG) structures, respectively. The proposed EBG is then placed between two Multiple-Input Multiple-Output (MIMO) DR antennas to reduce the MC level. As a result, an average of 7 dB level reduction is obtained. To further reduce the MC level, a thin MMW choke absorber wall is mounted vertically between the two DR antennas and above the EBG structure. An average of 22 dB MC reduction is achieved over the suggested bandwidth while maintaining good radiation characteristics. The measured isolation of the prototype antenna varies from -29 to -49 dB in the frequency range from 59.3 to 64.8 GHz. In fact, the proposed hybrid isolator outperforms other hybrid isolation techniques reported in the literature.

This work experimentally demonstrates a wide-angle beam steering based on an active conformal metasurface lens. Integrated with microwave varactors, the transmission phase of this cylindrical metasurface lens can be tuned in a range up to 195° by direct-current (DC) bias voltages. By compensating the phase difference between different incidences, the proposed cylindrical lens can collimate the incident spherical wave front into a plane wave front with predefined deflection angle. By increasing the number of feeding sources, the beam steering range of conformal lens can be expanded to ±60°. Having advantages of low cost and simple structure, the proposed conformal lens can be extended to millimeter-wave band and enable a wide range of applications.