Unidirectional Radiation Research Articles

Investigation on a smart textile heating concept for energy consumption-optimised heat transfer

Conventional non-stationary artificial heating methods, such as infrared radiators, have various deficits: The heat fields are small, their range is short, and the installation options are limited. In addition, they are environmentally harmful due to high emissions. To make in- and outdoor areas usable at lower temperatures, an energy consumption-optimized heat transfer is required. In this work we are investigating on an innovative, intelligent, modular textile for indoor and outdoor use. The use of conductive wires, sensors and a data-driven control circuit in the textile enables targeted heat radiation, which can be expanded as required thanks to its modular design. This reduces emissions and precisely controls energy consumption. By developing a demonstrator, the concept of the layered structure of the textile module, including unidirectional radiation and sensor technology, is being investigated. The conductive wires are incorporated into a flexible carrier material using a modified embroidery machine. In the process, the carrier material must meet the previously defined design requirements that are based on the material investigation and preliminary tests on embroidery feasibility. The structure of the intelligent textile is constructed, realized as a prototype, and validated. Through the combination of a heat source and flexible support material, it is possible to bring a competitive product to the market.

A Fluted E‐Shaped Antipodal Vivaldi Antenna With Rectangular Strips for Surface Scanning Application

ABSTRACTIn this paper, a fluted E‐shaped antipodal Vivaldi antenna (AVA) loaded with rectangular‐shaped strips is proposed for ground‐penetrating radar (GPR) application. The corrugation method is implemented by introducing multiple slots in the uppermost and lowermost arms of the antenna, followed by adding additional 10 strips to broaden and stabilize the impedance bandwidth. The electrical dimension of the antenna is 1.07λ × 1.8λ × 0.004λ. The proposed modified AVA (MAVA) exhibits a high fractional bandwidth of 144.8% over an ultrawideband of 1.6–10 GHz. The peak gain achieved by the antenna is 8.97 dBi. The proposed antenna offers a stable unidirectional radiation pattern along E‐ and H‐plane throughout the spectrum with maximum radiation efficiency of 96%. A prototype of the proposed antenna has been fabricated and tested where the measured results bear close resemblance with the simulated results. The pertinence of proposed antenna for GPR subsurface scanning was examined through a field test where scanned result signifies its aptness for such submissions.

Air-Gap Reduction and Antenna Positioning of an X-Band Bow Tie Slot Antenna on 2U CubeSats

In this research work, a small size and wide-band Bow Tie slot antenna (BTSA) is proposed and optimized for use on an unlimited lifetime small-sized CubeSats at X-band. Interestingly, this paper introduces a graceful mechanism of integrating Bow Tie slot antennas on the bodies of small CubeSat configurations, which minimizes the antenna throwing from the satellite body and the whole CubeSat volume. The proposed approaches propose and analyze in detail how a small metallic part of a 2U CubeSat body improves the antenna performances around an operating frequency of 8.4 GHz. It maximizes the antenna gain simultaneously with the beamwidth angles at 8.4 GHz by suppressing the resulting back-lobes, which are re-directed outside the CubeSat box. These impacts are achieved by shifting a very small air-gap distance of only 1 mm between the back face of the BTSA dielectric and the CubeSat top face. The developed BTSA is lightweight and exhibits a unidirectional radiation pattern with a wide beamwidth angle of about 160° and a high gain of about 11.0 dBi at 8.4 GHz. The overall results with occupied size and volume are satisfactory for unlimited lifetime CubeSat missions at X-band such as UM5-Ribat and UM5-EOSAT of University Mohammed V in Rabat.

Preparation of temperature-stable 0.8MgTiO3–0.2Mg2SiO4–0.06CaTiO3 microwave dielectric ceramics for unilateral radiating dielectric resonator antenna without ground plane

Unilateral radiating antennas are widely studied due to their ability to provide lateral or unidirectional radiation patterns, which are especially suitable for indoor and office Wi-Fi router applications. In this letter, a unilateral radiating rectangular dielectric resonator antenna (DRA) without a ground plane is proposed. A temperature stable low-loss 0.8MgTiO3–0.2Mg2SiO4–0.06CaTiO3 (MT–MS–CT) composite ceramic prepared via solid-state reaction and sintered at 1380 °C is utilized for the proposed DRA. Notably, the MT–MS–CT composite ceramic shows good dielectric performance with a permittivity of εr∼13, a quality factor of Q×f0∼115,000, Q = 1/dielectric loss, f0 = 8.6 GHz, and a temperature coefficient of resonant frequency TCF∼+4.6ppm/°C. Its unilateral radiation pattern is based on the complementary magnetic dipole and electric dipole, where the excited dominant TE111 mode of the rectangular DRA serves as the magnetic dipole and a probe acts as an electric dipole. The proposed prototype antenna fabricated using the composite ceramic has a unilateral radiation pattern with wide impedance bandwidth, reasonable gain, and radiation efficiency of 95%.

Gain and bandwidth enhancement using superstrate loaded 2×2 circular-array antenna for X-Band and RADAR applications

ABSTRACT This article demonstrates the fabrication, and measurements of a corporate offset-fed 2 × 2 array electromagnetically coupled patch (EMCP) circular-antenna based on the Fabry-Perot cavity principle. Single element antenna has a low gain of 6.28 dBi and is enhanced to 13.45dBi by loading the array with a superstrate. The antenna parameters −10 dB fractional bandwidth (FBW) and gain are improved by an air gap with 4-stacked circular patches and 4 stubs in the proposed design. The peak gain of the 2 × 2 array without superstrate was 8.88 dBi at 8.19 GHz, which is enhanced to 13.82 dBi at 9.55 GHz by parasitic loading and superstrate. The FBW of the proposed array antenna was enhanced by arranging four stubs between the 4-circles in the superstrate structure. The −10 dB FBW without stubs was 24.82% (7.62–9.73 GHz) and with stubs it became 38.47% (7.73–11.0 GHz). Adjustment of the height of the superstrate at 2.0 mm not only enhanced the gain and bandwidth but also advancement in the unidirectional radiation patterns. The array is prototyped is measured to validate the reflection coefficients and radiation characteristics and they found an excellent match with simulated results. The suggested array is most suitable for energy launchers in transitions, RADAR, military, satellite, X-band communications, and microwave laboratory applications.

Wideband star-shaped antenna based on artificial magnetic conductor surface for unidirectional radiation

Gathering the advantages of low profile, high gain, high efficiency, and wideband operation in a planar antenna is a challenging objective for the antenna designer. Low profile wideband antennas are usually characterized by low gain. An antenna of wideband impedance matching usually suffers continuous variations of the gain over such a wideband due to the variation of the radiation mechanisms and surface current distributions over the frequency band of impedance matching. Therefore, the motivation of the present work is to provide both impedance matching and stabilized high gain by the aid of wideband artificial magnetic conductor (AMC) with a design of the unit cell that is suitable to the antenna structure and the desired frequency band. The present work, proposes the utilization of low-size wideband AMS surface (AMCS) to be placed behind a wideband omnidirectional antenna to enhance the gain over the frequency band of operation. In this way, the radiating structure combines high gain and wideband operation in the same design. A wideband planar monopole printed antenna is designed to operate as omnidirectional antenna with perfect impedance matching and radiation efficiency over the frequency band 3.6-7.2GHz when placed in free space. The gain of the free-standing antenna varies from 2dBi to 4.5dBi over the frequency band. A wideband AMCS is designed to enhance the antenna gain over frequency band of operation. The designed AMCS is composed of only 3×3 unit cells and overall dimensions of 10×10cm. This surface is placed parallel to the planar antenna at a distance 1.7cm behind it. The enhanced gain of the radiating structure of the AMCS-backed antenna reaches 8.5dBi without affecting the bandwidth over which the input impedance is matched to the feeding line. The radiation efficiency of the AMCS-backed antenna is maintained above 98% over the frequency band of operation (3.7-7.2GHz). The wideband antenna and the AMCS are fabricated for practical evaluation of the overall AMCS-backed antenna performance including the measurements of impedance matching, gain and radiation efficiency. The measurements and simulation results are in good consent.

Formation of quasi-bound states in the continuum in a single deformed microcavity

Bound states in the continuum (BICs) hold significant promise in manipulating electromagnetic fields and reducing losses in optical structures, leading to advancements in fundamental research and practical applications. Despite their observation in various optical systems, the behavior of BIC in whispering-gallery-modes (WGMs) optical microcavities, essential components of photonic integrated chips, has yet to be thoroughly explored. In this study, we propose and experimentally identify a robust mechanism for generating quasi-BIC in a single deformed microcavity. By introducing boundary deformations, we construct stable unidirectional radiation channels as leaking continuum shared by different resonant modes and experimentally verify their external strong mode coupling. This results in drastically suppressed leaking loss of one originally long-lived resonance, manifested as more than a threefold enhancement of its quality (Q) factor, while the other short-lived resonance becomes more lossy, demonstrating the formation of Friedrich–Wintgen quasi-BICs as corroborated by the theoretical model and experimental data. This research will provide a practical approach to enhance the Q-factor of optical microcavities, opening up potential applications in the area of deformed microcavities, nonlinear optics, quantum optics, and integrated photonics.

Advanced Metamaterial-Integrated Dipole Array Antenna for Enhanced Gain in 5G Millimeter-Wave Bands

A metamaterial-based non-uniform dipole array antenna is presented for high gain 5G millimeter-wave applications with a wideband characteristic. Initially, a non-uniform dipole array is designed on a 0.202 mm thick Rogers RO4003C substrate, offering a wide operating bandwidth ranging from 23.1 GHz to 44.8 GHz. The dipole array antenna emits unidirectional end-fire radiation with a maximum gain of 8.1 dBi and an average gain of 6.7 dBi. Subsequently, to achieve high gain performance, a 5 × 7 metamaterial structure is designed in the direction of the antenna radiation. The implemented metamaterial structure is optimized for the operating frequency, enhancing the directivity of the antenna radiation and resulting in a gain increment of more than 3 dBi compared to the dipole array alone. The developed metamaterial-integrated dipole array antenna offers an operating bandwidth (S11 < −10 dB) of more than 21 GHz (63.92%), ranging from 23.1 GHz to 44.8 GHz, covering the most commonly used 5G millimeter-wave frequency bands (n257, n258, n259, n260, and n261). Furthermore, the presented antenna yields a stable high gain with a peak gain of 11.21 dBi and a good radiation efficiency of more than 64%. The proposed antenna is an excellent option for millimeter-wave 5G systems due to its overall properties, particularly its high gain and end-fire radiation characteristics, combined with a wide operating bandwidth.

Wideband circularly polarized reconfigurable metasurface antenna for 5G applications

Abstract A framework of a metasurface (MTS) – based wideband circularly polarized (CP) reconfigurable antenna for fifth generation (5G) wireless systems operating in the sub-6 GHz mid-frequency range is presented in this article. The proposed structure contains a simple patch antenna, which serves as the primary source, a shorting pin, two ring slots, and a metasurface superstrate. The shorting pin and two ring slots produce perturbation resulting in circular polarization with a narrow axial ratio (AR) bandwidth. A metasurface (MTS) superstrate composed of 4 × 4 rectangular patches stacked over the primary source antenna generates additional resonances that significantly improve the −10 dB impedance and 3 dB axial ratio (AR) bandwidth. Two PIN diodes are employed to alter the circular polarization between left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP). The prototype is made using an FR-4 epoxy substrate and has an overall size of 50 mm × 35 mm × 4.2 mm. The antenna has a −10 dB bandwidth of 44 % (4.0–6.2) and a 3 dB axial ratio bandwidth of 28 % (4.2–5.6). It also has a 3 dB beam width of 74° and 85° in the E and H planes, a gain of 7.1 dBi, cross-polar isolation of more than 15 dB, and a unidirectional radiation pattern. The simulated and measured results confirm that the implemented antenna is promising for sub-6 GHz 5G communication systems, particularly cognitive radio, wireless body area networks (WBAN), and satellite communication systems.

Offset-fed Slotted Antenna Practically Loaded with Split Ring as Water Quality Sensor for X-Band Industrial Applications

This article communicates an offset-fed split ring loaded slotted-antenna design, testing, and analysis for different water quality sensor. The antenna was designed to resonate at 10GHz on a low-cost FR-4 substrate of dimensions 0.621λo×0.467λo×.053λo, where λo is the free space wavelength. The measured antenna parameters are found in excellent agreements. The antenna achieves a gain of 7.61dBi with nearly unidirectional radiation pattern and a radiation efficiency of 76% at 10GHz. Further, the research is explored to use the antenna as a water sample sensor. Different water samples are tested with the antenna by dipping the antenna into the water samples and in the second case contactless measurements at 10mm apart from the upper water level in the container. The quality of water is examined by observing the shift in the resonant frequency (fr), antenna quality factor with different total dissolved solvents (TDS) water samples, and changes in the reflection coefficient (S11) values in the water samples. It is observed that the antenna shows less than 1.5% numerical sensitivity (NS) with fr and high NS with the S11. The S11 and bandwidth of the antenna vary with different water samples. This antenna is suitable for X-band industrial and microwave laboratory applications.

Metal‐loaded slot antenna with flat gain and one‐sided radiation

AbstractA metal‐loaded double‐layer unidirectional radiation slot antenna with flat gain is proposed for millimeter‐wave (mm‐wave) operations. Our presented antenna is constituted of a slot antenna with metal vias, an inner floating metal, a metal line, and ground patch. With the help of inner metal excited by the coupling of the slot antenna, an additional resonance point around 26 GHz could be obtained and the antenna gain is enhanced. To verify the design, the antenna has been fabricated with the prepreg technology. The whole fabricated size is only 0.62 × 0.62λ0² with a thickness of 0.057λ0 (λ0 is the free‐space wavelength at 26 GHz). The measured impedance bandwidth is from 25.1 to 26.55 GHz. Moreover, the proposed antenna obtains a wide flat gain (5.78 ± 0.48 dBi) within the bandwidth and stable one‐sided radiation patterns. The above characteristics show that the proposed antenna is a competitive choice for mm‐wave systems.

Tunable atomic spontaneous radiation in cylindrical waveguide

The chiral interaction between light and matter has brought chiral quantum optics into a flourishing stage. Here, we explore the perfect chiral interaction between the atoms with elliptically polarized dipoles and waveguide modes, and find that ideal unidirectional radiation can be obtained by adjusting the position and polarization of atoms. When there are two waveguide modes in the system, by controlling the polarization of the dipoles, the dipoles can radiate not only the unidirectional single waveguide mode, but also two seperated waveguide modes.

Nanoarchitectonics of MXene-based sixteenth-mode flexible SIW antenna for conformal wireless applications

A miniaturized sixteenth-mode nanomaterial-based flexible substrate-integrated waveguide (SIW) antenna is demonstrated at an operating frequency of 3.5 GHz. The antenna is designed based on the one-sixteenth mode of a circular SIW cavity. The SIW in this instance is manufactured exclusively with flexible non-textile materials, which makes it unique and novel from the other reported works. The substrate of the proposed antenna is manufactured using PDMS by masking and laser cutting process. The patch on the substrate is made of a 2D nanomaterial MXene, whereas the ground at the bottom is created using copper tape. Vias connecting the patch and ground were filled with silver paste and dried at 80 °C in an oven. With a compact design and flexibility, the proposed flexible SIW antenna offers a unidirectional radiation pattern with a reasonable gain of −3.39 dBi at a 3.5 GHz resonant frequency. Additionally, the antenna is demonstrated for its flexible performance by straining it to the maximum extent without any structural damage. Consequently, the presented flexible SIW antenna can be well suited for conformal wireless applications.

Piezo‐Turned Magnet Rotation for ELF/SLF Cross‐Medium Communication in Omni‐Direction

AbstractExtremely/super low frequency (ELF/SLF) electromagnetic (EM) waves offer efficient propagation in challenging cross‐medium environments. However, conventional coil antennas, when emitting ELF/SLF EM waves, face constraints related to size, radiation efficiency, and high power consumption. To overcome these limitations, a disc‐rod structured piezoelectric rotating resonator is proposed, which can turn a NdFeB permanent magnet disc into rotation with an impressive high‐speed up to 10 000 r min−1 via wobbling motion of the rod tip, effectively generating ELF/SLF magnetic field radiation via rotational oscillation other than common linear and swinging oscillation of the magnetic dipole moments. The piezo‐turned magnetic rotation (PTMR) method leads to a two to five‐fold enhancement in magnetic field emission compared to existing piezo‐actuated acoustic resonant antennas, and a 370 times higher emitting efficiency compared to the traditional coil antenna with a comparable size. In contrast to unidirectional EM wave radiation at their solely resonant frequencies, the PTMR antenna showcases omnidirectional B‐field radiation with continuous tunability in a dual frequency band spanning from 10 to 100 Hz. Moreover, an air–seawater cross‐medium magnetic field communication is successfully demonstrated. With outstanding performance metrics, the PTMR antenna emerges as a promising solution for efficient long‐distance ELF/SLF cross‐medium communication.

A Ku‐band wideband low‐profile patch antenna with slot‐loading and parasitic structures

AbstractThis letter introduces a novel bandwidth‐enhanced low‐profile (thin structure) patch antenna adopting double U‐slot loading and parasitic structures. The proposed antenna features single‐layer topology, thin structure of 0.027 , enhanced −10 dB impedance bandwidth of 12.5%, and unidirectional radiation pattern at Ku‐band. Performances of the proposed antenna are validated through full‐wave simulations and measurements. The proposed antenna element is further duplicated to form a patch antenna array, with the parasitic structures shared by adjacent elements. The proposed antenna demonstrates potential in applications demanding wideband, highly directional radiation, and thin structure for seamless integration.

A METAMATERIAL SLOTTED PATCH ANTENNA WITH METASURFACE

In this project, a novel, compact, high-gain, directive, and superstrate configuration-based metasurface (MS) antenna has been designed, which incorporates a fractal-shaped slotted patch having a periodic arrangement of square patches along with a shorting via at its center and a couple of rectangular slots in the ground plane. The MS is designed over the FR4 dielectric by introducing a periodic arrangement of unit cells in which the unit cell is structured by a S-type patterned patches. The MS is separated by a layer from the conventional patch antenna designed over the FR4 dielectric, thereby acting as a superstrate. The proposed antenna provides good impedance matching across the frequency region of 10.14–10.94 GHz with a unidirectional radiation pattern. A maximum return loss of -18.4dB have been realized at 10.2GHz. As the proposed antenna is more efficient, it can be promoted for X-band operations, such as satellite communication, defense purpose, and medical supervision. Keywords— Metasurface (MS), microstrip, slotted fractal patch, superstrate.

Design and investigation of cavity backed bowtie antenna with unidirectional radiation pattern using characteristic mode analysis

Abstract In this work, a novel cavity backed leaf-shaped bowtie antenna is designed using Characteristic Mode Analysis (CMA). An analytical expression is proposed to arrive at the leaf shape of the bowtie antenna using optimization process. The developed antenna is backed by a square-cavity to get unidirectional radiation pattern with high gain and good front-to-back-ratio characteristics. CMA technique is used in the design and optimization of the cavity structure and generalized design equation is proposed to design the cavity for getting good impedance bandwidth and broadside radiation characteristics in the Desired Band of Interest (DBI). The developed antenna resonates from 0.8 to 4.3 GHz with stable and unidirectional radiation characteristics giving maximum gain and FBR of 11.5 dBi and 15.2 dB respectively, making it suitable for Ground Penetrating Radar (GPR) applications.

Thermal-structural analysis of a large space hoop-column antenna under unidirectional solar radiations

A thermal-structural coupling analysis model of the hoop-column antenna is established with considering of the mutual influence between the deformation and heat conduction of the cable net and thin-walled tube truss in the antenna. In this model, the circumferential temperature gradient of the thin-walled tube is considered by using the Fourier thermal element model, while only the axial heat conduction is considered in the cable thermal analysis model. The accuracy of the established thermal-structural coupling analysis models of the cable and tube beam are verified by two numerical tests. Modal analysis as well as the frequency sensitivity analysis with respective to several structure parameters are performed. The modal analysis results are also verified by finite element (FE) simulation using the commercial FE software ANSYS. Thermal-structural coupling performances of the hoop-column antenna with and without considering of the reflector shadow effect being considered are conducted and compared through the established model. Temperature fields and displacements of the hoop-column antenna under unidirectional solar heat flux shocks in different directions are also calculated and compared. On this basis, influences of some key structural parameters on temperature and deformation of the hoop-column antenna are also examined. The thermal-structural coupling dynamic model established in this work can contribute to the early design of the hoop-column antenna.

Self‐isolated quadruplexing SIW antenna with extremely low frequency ratio for C‐band applications

AbstractIn this letter, an substrate integrated waveguide ‐based self‐quadplexing antenna based on a modified Jerusalem cross‐shaped slot is presented. By introducing different lengths of the slots of Jerusalem cross, the antenna operates at four different closely spaced resonant frequencies 4.08, 4.37, 4.61, and 4.97 GHz. The proposed quadplexer antenna achieved a minimum port isolation of 20 dB between any two ports with an extremely low frequency ratio of 1.2. The quadplexer antenna has unidirectional radiation pattern and independent frequency tunability characteristics with a gain of 6.88, 6.51, 7.03, and 7.12 dBi, at corresponding resonant frequencies and a compact size of 0.142, where 0 is the free space wavelength at the lowest resonant frequency. The proposed antenna is suitable for C‐band multiplexing applications.

Compact Archimedean spiral antenna with high gain for electrostatic discharge detection

AbstractA compact Archimedean spiral antenna with high gain for electrostatic discharge (ESD) detection is investigated. A frustum‐shaped cavity proposed in this work is formed to optimise the maximum antenna gain. Additionally, a helix arm is loaded to enhance antenna gain in lower band. The measured results demonstrate that the proposed antenna, which employs a unidirectional radiation mode, exhibits a maximum antenna gain ranging from −0.74 dBi to 9.46 dBi and a voltage standing wave ratio less than 3 across a frequency range of 0.65–5 GHz. A test system consisted of proposed antenna and a commercial ESD detection antenna is established. The verified results indicate that the proposed antenna has a performance close to the commercial antenna, so that proposed antenna with compact size is preferred to be utilised for ESD detection.