Unidirectional Radiation Research Articles

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.

Design of circularly polarized antenna with wide overlapped axial‐ratio and gain beamwidths for upper hemispherical coverage

AbstractIn this letter, a circularly polarized antenna with wide overlapped axial ratio and gain beamwidth is proposed for upper hemispherical coverage. By bending half of the dipoles to the vertical direction, and connecting eight metal columns to the ground, the half‐power beamwidth (HPBW) of all cut planes can be increased effectively. On the basis, one reactive impedance structure is applied as the reflector to achieve unidirectional radiation, as well as increase the 3‐dB axial ratio beamwidth (ARBW) of the antenna. Miniaturized four‐feed networks are utilized to provide excitation, and the shielding technique is applied to reduce its influences on the antenna radiation performances. Measurements show that the proposed antenna can operate in the range of 1.51–1.59 GHz, which covers the upper band of global navigation satellite system (GNSS). Besides, at 1.561 GHz, the measured HPBWs and 3‐dB ARBWs are larger than 131° and 135° in all cut planes. The wide overlapped beamwidth of the proposed antenna with small size indicates the potential applications in high‐precision GNSS navigations.

Ag-cap-enhanced upconversion luminescence of micropillars with unidirectional radiation

Exploration of plasmonic structures to enhance upconversion luminescence (UCL) attracts attention because faint UCL from a material is a bottleneck for its applications. We designed and prepared three easily realized structures to improve the UCL of β-NaYF4:Yb3, Er3+ micropillar (MP), and compared them to a reference structure on glass on single particles. We achieved a 43-fold UCL enhancement with the MPs with an Ag cap.The experimental results and simulations indicated that the improvements in excitation field and radiation direction collectively enhanced the MP UCL. We validated the captured radiation patterns generated from various structures by excitation simulations and provide a rational criterion for cavity design.

Magnetic-electric dipole circularly polarized antenna with unidirectional radiation pattern with improved characteristics

Abstract In this paper, a compact unidirectional antenna consisting of a planar electric dipole and a shortened connecting element is introduced. This antenna is excited by a Γ-shaped feeding line. A wide impedance bandwidth in the frequency range of 1.3–3.3 GHz is observed in the output performance. Sufficient main lobe and low level back lobe have been introduced as other characteristics of the structure, based on radiation patterns. The antenna design process is evaluated step-by-step and using parametric study based on the antenna geometry. One of the main features of the desired antenna is the realization of circular polarization in a high percentage of the operational bandwidth 1.5–3.3 GHz. The radiation patterns of the orthogonal planes E-field and H-field along with the left-handed and right-handed circular polarization patterns for the desired antenna have been extracted and analyzed. A three-dimensional structure in the form of stacked stepped disks (SSD) is introduced to increase overall performance of antenna. There is an acceptable similarity between the E-field and H-field page patterns, which shows the accuracy of the design process. On the other hand, for studying the circular polarization, left-handed and right-handed patterns based on the main beam direction and orthogonal polarization level have acceptable performance. The maximum overall gain of the antenna in the designed frequency band is near to 13 dB.

Novel Unidirectional Radiation Principle by Backward Field Cancellation and Its Application to Wearable IoT Devices

Novel Unidirectional Radiation Principle by Backward Field Cancellation and Its Application to Wearable IoT Devices

Broadband Miniaturized C-Band Stacked Antenna Design and Analysis Using TLM

This paper presents the design of broadband miniaturized C-band stacked antenna and its analysis using TLM . The proposed antenna operates at C-band and acquires 45% bandwidth with a peak gain of 8 dBi. The generalized transmission-line model, developed earlier for the analysis of multilayered stacked antennas (without slots), has been implemented and modified for the analysis of the proposed antenna (having a slot in the driven patch). The slot coupling effect is incorporated in the modified TLM model for the circuit-level simulation and analysis of the designed antenna. Circuit simulation results agree with EM simulation and measured results. The proposed antenna occupies an overall volume of 52 × 50 × 4.5 mm3, while volume of the radiating elements is 13 × 19.89 × 4.5 mm3, which makes the design quite compact. The proposed stable antenna has unidirectional radiation patterns throughout the band of operation and is thus suitable for applications such as remote sensing, target detection, and imaging.

2.3 Ghz Lte Antenna Design Using Triangle Geometry and Array Structure

Microstrip antenna is one of the most important devices in telecommunications systems. One example is the design of a microstrip antenna on a long time evolution (LTE) device. Disadvantages of this microstrip antenna include low gain, poor directionality, low efficiency, resistance losses on the feed line and narrow bandwidth. This research will design a triangular patch array microstrip antenna to increase the gain so that it can meet the desired work specifications with a working frequency of 2.300MHz. The antenna is designed using FR-4 Epoxy substrate material with a size of 120 mm x 60 mm, which has a dielectric constant (?r) of 4.3, a loss tangent of 0.035 and a material thickness of 1.6 mm. Antenna designed using CST studio suite software 2018. The results obtained in the working frequency band 2280.4 MHz – 2370.0 Mhz, middle frequency 2332 MHz, return loss – 47.360dB, bandwidth 24.7MHz, VSWR 1.008, gain 4.39dBi, impedance 49.90 , and unidirectional radiation pattern.