Search

This paper presents experimental verification results for a finite‐sized array of a simple non‐reciprocal metasurface elements. The metasurface elements consists of ferrite loaded metal patches. Experimental results demonstrate nonreciprocity, achieving isolation exceeding 20 dB at 6.4 GHz in a 2×2 array. Additionally, these findings are compared with simulation results for a 4×4 array to validate its practicality in a finite array setting. [ABSTRACT FROM AUTHOR]

Additive manufacturing has emerged as a transformative methodology in numerous engineering domains, with the fabrication of antennas and electromagnetic devices being a promising application area. This study presents a comprehensive review of the application of these technologies for manufacturing electromagnetic devices, offering a categorized analysis based on different types of additive manufacturing techniques. Each category is examined, and its characteristics are briefly described, highlighting not only the most innovative and significant devices fabricated using specific technologies, but also identifying their limitations and strengths. Through a dual analysis, this paper provides a deep understanding of the potential of and challenges associated with using different additive manufacturing technologies in the design and crafting of electromagnetic components. Moreover, this review offers recommendations for future studies, suggesting how the unique features of this new manufacturing paradigm could be further leveraged for breakthroughs in the electromagnetic field. [ABSTRACT FROM AUTHOR]

Respiratory problems are common amongst older people. The rapid increase in the ageing population has led to a need for developing technologies that can monitor such conditions unobtrusively. This paper presents a novel study that investigates Wi-Fi and ultra-wideband (UWB) antenna sensors to simultaneously monitor two different breathing parameters: respiratory rate, and exhaled breath. Experiments were carried out with two subjects undergoing three breathing cases in breaths per minute (BPM): (1) slow breathing (12 BPM), (2) moderate breathing (20 BPM), and (3) fast breathing (28 BPM). Respiratory rates were captured by Wi-Fi sensors, and the data were processed to extract the respiration rates and compared with a metronome that controlled the subjects' breathing. On the other hand, exhaled breath data were captured by a UWB antenna using a vector network analyser (VNA). Corresponding reflection coefficient data (S11) were obtained from the subjects at the time of exhalation and compared with S11 in free space. The exhaled breath data from the UWB antenna were compared with relative humidity, which was measured with a digital psychrometer during the breathing exercises to determine whether a correlation existed between the exhaled breath's water vapour content and recorded S11 data. Finally, captured respiratory rate and exhaled breath data from the antenna sensors were compared to determine whether a correlation existed between the two parameters. The results showed that the antenna sensors were capable of capturing both parameters simultaneously. However, it was found that the two parameters were uncorrelated and independent of one another. [ABSTRACT FROM AUTHOR]

Ever‐increasing bandwidth requirements from various industries drive the need for the ever‐increasing bandwidth of antennas used for testing. Broadband Double‐Ridged Guide Horn (DRGH) antennas are used extensively in antenna measurement and ElectroMagnetic Compatibility/Interference (EMC/I) testing. The current state‐of‐the‐art broadband DRGH antennas reported in the literature for use in measurement applications cover bandwidth ratios as large as 36:1 (0.5–18 GHz). This paper presents the design and realisation of a DRGH antenna with a 100:1 bandwidth ratio (0.5–50 GHz). To achieve such a wide bandwidth, the ridge gap, width and feed were optimised, and a novel coaxial‐to‐ridge waveguide launcher section based on a typical Vivaldi antenna was developed. Backward radiation was reduced using an absorber‐filled cavity. A prototype DRGH antenna was manufactured using additive manufacturing, also referred to as 3D printing. Simulated and measured results obtained in an anechoic chamber are presented. [ABSTRACT FROM AUTHOR]

This paper proposes an all‐metal wideband circularly polarized (CP) single‐patch antenna based on TM11 mode. The conventional square patch is divided into four small square patch units by loading metal shorting walls under the two vertical centerlines. The shorting walls are windowed to facilitate coupling between the adjacent units. When the TM11 mode is excited, the coupling windows not only distribute energy but also provide the 90° phase difference required for CP radiation. An additional feeding network is not required, and its profile is less than 0.05λ0 (λ0 is the free space wavelength at the center frequency). Three minima in the axial ratio (AR) response are present. The results show that right‐hand circularly polarized (RHCP) radiation is achieved. The measured 3 dB AR bandwidth is 6.9%, ranging from 1.52 to 1.62 GHz, and the RHCP realized peak gain is 7.72 dBic. An all‐metal construction suitable for satellite communication systems is designed that has superior performance in harsh space environments. [ABSTRACT FROM AUTHOR]

Ground penetrating radar (GPR) is regulated regarding emission limits for ultra‐wideband in a number of jurisdictions. The definitions of these regulations employ concepts and terminology that are more suited to traditional narrow band radio transmitters. Further, the emissions limits were based on limited quantitative factual information and have resulted in stringent limitations on GPR technology advancement. Factual theoretical and experimental information on the emissions from actual GPR devices is not generally available, and the relationship with regulatory requirements is poorly understood by users. This information gap must be filled if a compelling argument for less stringent emissions levels is to be mounted in the future. Moreover, the current regulations have the potential to trigger further review of emission limits in the future which could be detrimental to the use of GPR. In this paper, we present the basic steps entailed in translating impulse time‐domain GPR instrument behaviour into 'regulatory' parameters. To achieve this, we also employ three‐dimensional finite‐difference time‐domain numerical modelling to simulate the transient electromagnetic field variation around dipole antennas placed on the surface of a half‐space or at a height over it to illustrate the dependency on sensor height and ground permittivity. The ultimate goal is to establish the foundation for more sensible rule making, if and when, the regulatory standards come under scrutiny for revision and further user understanding. [ABSTRACT FROM AUTHOR]

In this paper we present details of the construction of a wideband, cryogenic receiver and its successful commissioning on the Arecibo Observatory 12 m telescope. The cryogenic receiver works in the 2.5–14 GHz frequency range. We upgraded the current narrow band, room temperature receivers of the telescope with the new wideband receiver. The current receiver is built around a Quadruple‐Ridged Flared Horn (QRFH) developed by Akgiray et al. (2013, https://doi.org/10.1109/tap.2012.2229953). To mitigate strong radio frequency interference (RFI) below 2.7 GHz, we installed a highpass filter before the first stage low noise amplifier (LNA). The QRFH, highpass filter, noise coupler and LNA are located inside a cryostat and are cooled to 15 K. The measured receiver temperature is 25 K (median value) over 2.5–14 GHz. The system temperature measured at zenith is about 40 K near 3.1 and 8.6 GHz and the zenith antenna gains are 0.025 and 0.018 K/Jy at the two frequencies respectively. We recommend the following improvements to the telescope system: (a) Upgrade the highpass filter to achieve better RFI rejection near 2.5 GHz; (b) Improve aperture efficiency at 8.6 GHz; (c) Upgrade the intermediate frequency system to increase the upper frequency of operation from 12 to 14 GHz. Key Points: Successful commissioning of a wideband, cryogenic receiver for the 12 m telescope at the Arecibo ObservatoryAchieved system temperature of 40 K and gains of 0.025 K/Jy and 0.018 K/Jy at frequencies 3.1 and 8.6 GHz respectively [ABSTRACT FROM AUTHOR]

Inspired by the concept of frequency‐independent antennas in the electromagnetics, which theoretically exhibit a frequency‐independent bandwidth, this paper extends the concept to acoustics by adopting a log‐spiral and its modified shape to introduce a class of metamaterials called frequency‐independent sound‐absorbing metamaterials. Without the requirement of multiple resonators, these metamaterials achieve an ultra‐broadband absorption spanning from 550 Hz for a wide range of incident angles up to 80°, using a single unit cell structure owing to Fabry–Pérot resonance, viscous boundary losses, and thermoviscous loss of the foam. Numerical and experimental analyses are provided to demonstrate the working principles of the proposed structures. Their performance is compared with archimedean spiral, and the influence of air and porous material parameters on the performance of the metamaterial is discussed in detail for normal and oblique incident waves. The underlying principle is discussed in detail, highlighting the distinctions between the proposed structures and state‐of‐the‐art broadband metamaterials. The proposed structures represent a pioneering advancement in the field by offering compact and ultra‐broadband sound‐absorbing metamaterials that are suitable for practical applications. [ABSTRACT FROM AUTHOR]

Very‐low‐frequency (VLF) transmitting antennas have a crucial influence on the nearby electromagnetic environment. Commercial software packages, such as CST Studio Suite (CST) or Altair FEKO (FEKO), are always utilised to calculate the electric fields of VLF antennas, which consume considerable computing resources and time. The classical method of electric field calculation, the charge simulation method (CSM), is first applied to the calculation of electric field near the VLF transmitting antenna. The distribution characteristics of three‐dimensional electric fields were analysed. The electric field surrounding the antenna exhibited axial symmetry. The highest electric field strength was at the top of the antenna, and as the distance from the antenna increased, the electric field strength exponentially decreased. The comparisons are performed between the results of the CSM and those of commercial software, the average relative errors of CSM on two observation paths are very small, 2.20% and 2.21%, respectively. Meanwhile, the CSM shows considerable advantages in saving calculation resources and improving efficiency. Additionally, the comparison between CSM calculation and the measured data is carried out. The results show that this method can accurately calculate the electric field near VLF transmitting antenna and offer valuable insights and a new solution. [ABSTRACT FROM AUTHOR]

Microstrip patch antennas have been widely used in contemporary mobile communication technology, including 5G. Previous studies in the area have shown that such antennas can be optimized to operate in different bands of 5G. This study proposes a microstrip patch antenna designed to operate at 26 and 28 GHz and aimed at improving the gain and other radiation characteristics by adding a combination of different slot shapes to a single rectangular patch that is very common and popular in 5G antennas. The results show that the gain is noticeably increased by inserting two hammer slots and a rectangular slot in the middle between them. The dimensions of the slots are optimized using the CST Studio Suite simulator. A comparative analysis was performed to demonstrate the superiority of the proposed over previous designs in terms of gain value and other radiation parameters. The results suggest that such a very simple and low-profile antenna can be a good candidate for 5G mobile applications. [ABSTRACT FROM AUTHOR]

Abstract Ever‐increasing bandwidth requirements from various industries drive the need for the ever‐increasing bandwidth of antennas used for testing. Broadband Double‐Ridged Guide Horn (DRGH) antennas are used extensively in antenna measurement and ElectroMagnetic Compatibility/Interference (EMC/I) testing. The current state‐of‐the‐art broadband DRGH antennas reported in the literature for use in measurement applications cover bandwidth ratios as large as 36:1 (0.5–18 GHz). This paper presents the design and realisation of a DRGH antenna with a 100:1 bandwidth ratio (0.5–50 GHz). To achieve such a wide bandwidth, the ridge gap, width and feed were optimised, and a novel coaxial‐to‐ridge waveguide launcher section based on a typical Vivaldi antenna was developed. Backward radiation was reduced using an absorber‐filled cavity. A prototype DRGH antenna was manufactured using additive manufacturing, also referred to as 3D printing. Simulated and measured results obtained in an anechoic chamber are presented.

The rapid development of ultrawideband (UWB) communication systems has resulted in increasing performance requirements for the antenna system. In addition to a wide bandwidth, fast propagation rates and compact dimensions, flexibility, wearability or portability are also desirable for UWB antennas, as are excellent notch characteristics. Although progress has been made in the development of flexible/wearable antennas desired notch properties are still rather limited. Moreover, most presently available flexible UWB antennas are fabricated using environmentally not attractive subtractive etching-based processes. The usage of facile additive sustainably inkjet printing processes also utilizing low temperature plasma-activated conductive inks is rarely reported. In addition, the currently used tri-notched flexible UWB antenna designs have a relatively large footprint, which poses difficulties when integrated into miniaturized and compact communication devices. In this work, a silver nano ink is used to fabricate the antenna via inkjet printing and an efficient plasma sintering procedure. For the targeted UWB applications miniaturized tri-notched flexible antenna is realized on a flexible polyethylene terephthalate (PET) substrate with a compact size of 17.6 mm × 16 mm × 0.12 mm. The antenna operates in the UWB frequency band (2.9–10.61 GHz), and can shield interferences from WiMAX (3.3–3.6 GHz), WLAN (5.150–5.825 GHz) and X-uplink (7.9–8.4 GHz) bands, as well as exhibits a certain of bendability. Three nested "C" slots of different sizes were adopted to achieve notch features. The simulation and test results demonstrate that the proposed antenna can generate signal radiation in the desired UWB frequency band while retaining the desired notch properties and having acceptable SAR values on-body, making it a viable candidate for usage in flexible or wearable communication transmission devices. The research provides a facile and highly efficient method for fabricating flexible/wearable UWB antennas, that is, the effective combination of inkjet printing processing, flexible substrates, low temperature-activated conductive ink and antenna structure design. [ABSTRACT FROM AUTHOR]

The design and optimisation of a five‐cascade layer Rotman Lens based on waveguide with a graded refractive index at Ka‐band frequency are presented. The proposed lens incorporates 5 layers within the cavity, utilises a modified three focal Rotman lens design methodology to achieve perfect phasing for true time delay beam steering, and optimises each layer's parameters such as refractive index, vertex location, and contour angle to improve insertion loss between input ports and output array elements. This approach enhances energy concentration between input and output ports, reducing spillover to dummy ports. The graded layers are formed using periodic cubic metallic posts with varying heights within a parallel plate waveguide. The results show an average improvement in the insertion loss of 16% and a peak improvement of 48% across the bandwidth when compared to conventional Rotman lenses. The normalised average phase error across the array elements for all beam ports excitation is 4 × 10−3 and the peak degradation of the main beam during beam scanning from 0° to ±22° varies from 0.7 to 1 dB at different frequencies operating in the Ka‐band (24–30 GHz) with potential applications for 5G communications. The simulation results demonstrate good agreement with the measurement results. [ABSTRACT FROM AUTHOR]

A review on planar printed structures that are based on Matryoshka-like geometries is presented. These structures use the well-known principle of Matryoshka dolls that are successively nested inside each other. The well-known advantages of the planar printed technology and of the meandered nested Matryoshka geometries are combined to generate miniaturized, multi-resonance, and/or wideband configurations. Both metal and complementary slot structures are considered. Closed and open configurations were analyzed. The working principles were explored in order to obtain physical insight into their behavior. Low-cost and single-layer applications as frequency-selective surfaces, filters, antennas, and sensors, in the microwave frequency region, were reviewed. Potential future research perspectives and new applications are then discussed. [ABSTRACT FROM AUTHOR]

Recent advancements in onboard satellite communication have enhanced the capability of dynamically modifying the radiation pattern of a Direct Radiating Array (DRA). This is crucial not only for conventional communication satellites like Geostationary Orbit (GEO) but also for those in lower orbits such as Low Earth Orbit (LEO). Key design factors include the number of beams, beamwidth, Effective Isotropic Radiated Power (EIRP), and Side Lobe Level (SLL) for each beam. However, a challenge arises in multibeam scenarios when trying to simultaneously meet requirements for the aforementioned design factors which are reflected as uneven power distribution. This leads to over-saturation, especially in centrally located antenna elements due to the activation times per beam, commonly referred to as activation instances. In response to this challenge, this paper presents a method to balance the activation instances across antenna elements for each required beam. Our focus is on beams operating at 19 GHz on a CubeSat positioned 500 km above the Earth’s surface. We introduce a Genetic Algorithm (GA)-based algorithm to optimize the beamforming coefficients by modulating the amplitude component of the weight matrix for each antenna element. A key constraint of this algorithm is a limit on activation instances per element, which avoids over-saturation in the Radio Frequency (RF) chain. Additionally, the algorithm accommodates beam requirements such as beamwidth, SLL, pointing direction, and total available power. With the previous key design factors, the algorithm will optimize the required genes to address the desired beam characteristics and constraints. We tested the algorithm’s effectiveness in three scenarios using an $8\times 8$ DRA patch antenna with circular polarization, arranged in a triangular lattice. The results demonstrate that our algorithm not only meets the required beam pattern specifications but also ensures a uniform activation distribution across the antenna array.

In this paper, the prototypical deployment of a Multiple-Input-Multiple-Output (MIMO) antennas system, denoted as Smart Selective Antennas System (SSAS), aiming at mitigating inter-cell interference effects of cellular networks for in-flight Unmanned Aerial Vehicles (UAVs), is discussed. In detail, the proposed SSAS is beneficial to increase the communication reliability over existing cellular networks, especially with regard to complex Beyond Visual Line of Sight (BVLOS) drones’ missions and applications. Its deployment is motivated as existing 4G Long Term Evolution (LTE) cellular networks (as well as 5G networks) are mainly designed and optimized for terrestrial utilization, thus not taking into account interference effects on flying connected devices. The prototypical implementation of the SSAS has been expedient to conduct multiple experimental flights with a drone at different altitudes, collecting performance results and validating the proposed SSAS as a viable solution for inter-cell interference mitigation.

Low‐cost passive reconfigurable intelligent surfaces that provide coverage expansion in wireless communication networks are facing challenges in phase shift optimization due to limitations in acquiring channel information for sub‐channels. To overcome this, a new approach that improves both the convergence speed and overall performance relative to the existing state‐of‐the‐art scheme is proposed. Experimental results in an environment with a Rician factor of 20 showed a 9.3% increase in the average sum data rate, and the probability of the sum data rate exceeding the threshold of 10 increased by 30%. [ABSTRACT FROM AUTHOR]

The evolution of communication systems has brought about a paradigm shift, particularly in radiocommunications, where software has increasingly taken precedence over hardware. This transition has not only reduced implementation costs but has also significantly enhanced the flexibility of equipment architecture. A prime example of this trend is the emergence and consolidation of softwaredefined radio (SDR) technology in recent decades. This study provides a comprehensive contextualization of SDR technology, offering insights into its current state in terms of development tools and market equipment. Additionally, two learning scenarios are presented that employ different teaching methodologies. In one of these scenarios, communication theory is exclusively approached from a theoretical perspective. In the second scenario, knowledge acquisition is encouraged through the implementation of low-cost laboratories that incorporate SDR technology. The study indicates that implementing SDR technology boosts student motivation and learning, with 73.13% believing it enhances engineering education and 96% showing increased motivation. Those using SDR in practical laboratories perform better on knowledge tests, but statistical analysis shows that the difference is not statistically significant. [ABSTRACT FROM AUTHOR]

Abstract This paper proposes an all‐metal wideband circularly polarized (CP) single‐patch antenna based on TM11 mode. The conventional square patch is divided into four small square patch units by loading metal shorting walls under the two vertical centerlines. The shorting walls are windowed to facilitate coupling between the adjacent units. When the TM11 mode is excited, the coupling windows not only distribute energy but also provide the 90° phase difference required for CP radiation. An additional feeding network is not required, and its profile is less than 0.05λ0 (λ0 is the free space wavelength at the center frequency). Three minima in the axial ratio (AR) response are present. The results show that right‐hand circularly polarized (RHCP) radiation is achieved. The measured 3 dB AR bandwidth is 6.9%, ranging from 1.52 to 1.62 GHz, and the RHCP realized peak gain is 7.72 dBic. An all‐metal construction suitable for satellite communication systems is designed that has superior performance in harsh space environments.

A dual‐mode dielectric resonator antenna based on a microstrip line‐slot coupling feed, operating in both the GMS‐900 and GMS‐1800 frequency bands, is presented. The antenna structure consists of a rectangular dielectric substrate and a cylindrical dielectric resonator, which is fed by a microstrip line‐slot coupling. The cylindrical resonant cavity and the dual‐stub coupling slot are designed so that the HEM111 and HEM311 modes are excited simultaneously, resulting in resonance at the two desired frequency points. The gain of the antenna is 3.74 and 7.63 dBi at 0.9 and 1.8 GHz respectively, and the efficiency of the antenna is greater than 70% in both operating bands. [ABSTRACT FROM AUTHOR]

Respiratory problems are common amongst older people. The rapid increase in the ageing population has led to a need for developing technologies that can monitor such conditions unobtrusively. This paper presents a novel study that investigates Wi-Fi and ultra-wideband (UWB) antenna sensors to simultaneously monitor two different breathing parameters: respiratory rate, and exhaled breath. Experiments were carried out with two subjects undergoing three breathing cases in breaths per minute (BPM): (1) slow breathing (12 BPM), (2) moderate breathing (20 BPM), and (3) fast breathing (28 BPM). Respiratory rates were captured by Wi-Fi sensors, and the data were processed to extract the respiration rates and compared with a metronome that controlled the subjects’ breathing. On the other hand, exhaled breath data were captured by a UWB antenna using a vector network analyser (VNA). Corresponding reflection coefficient data (S11) were obtained from the subjects at the time of exhalation and compared with S11 in free space. The exhaled breath data from the UWB antenna were compared with relative humidity, which was measured with a digital psychrometer during the breathing exercises to determine whether a correlation existed between the exhaled breath’s water vapour content and recorded S11 data. Finally, captured respiratory rate and exhaled breath data from the antenna sensors were compared to determine whether a correlation existed between the two parameters. The results showed that the antenna sensors were capable of capturing both parameters simultaneously. However, it was found that the two parameters were uncorrelated and independent of one another.

This paper is about sustainable Electromagnetic Metamaterials (EM-MM), which are a new class of artificial materials with unique electromagnetic properties that cannot be found in nature. These materials are made from discrete micro and nanoscale objects which resonate, allowing for precise control over how they interact with electromagnetic waves, and hence, leading to unheard of functionalities. Thus the need for sustainable synthesis methods for EM-MM has become paramount to mitigate the quantity of resources associated with conventional fabrication techniques. Renewable resources like biopolymers that mimic natural patterns are examples of the sustainable use of bio based synthetic material pathways. This may guarantee sustainability through fabricating additive manufacturing strategies, especially 3D printing innovation where fabric statement is controlled only as required, diminishing waste. With all this recycling and up cycling offer opportunities for development and cost reduction while reducing the natural impacts related to sustainability. There are several different domains have benefited from the application of EM MM, for example solar energy harvesting offer potential for sustainable power generation, imaging uses met material lenses which have superior resolution and sensitivity, while in telecommunications met material antennas ensure to transmit and get signals more successfully. But there are still a few issues that still need to be resolved in electromagnetic met materials. Future directions include the research of incorporating a plan of new types of electromagnetic composites with upgraded qualities and sustainable synthesis strategies. Applications of technology require to overcome practical challenges such as integration, toughness, and cost-effectiveness while assessing societal implications, financial, and social affects. For the sustainable advancement of metamaterials in order to deal with major societal concerns, minimizing their natural impressions requires collaboration and moral concerns.