Disk Antenna Research Articles

Passive Wireless Partial Discharge Sensors with Multiple Resonances.

Partial discharge (PD) is the dominant insulating defect in Gas-Insulated Switchgear (GIS). The existing detection methods are mainly divided into built-in wire-connected disk antennas with destructive drilling and external ultra-high frequency antennas with poor anti-interference ability. This research introduces a passive wireless PD sensor implanted inside GIS on the observation window. The sensor is implemented by a sheeting branch-inductor with multiple resonances which is able to enhance detection sensitivity. A coaxially aligned readout circuit, positioned outside the GIS, interrogates the PD sensor to wirelessly obtain the PD signal. The proposed sensing scheme improves signal-to-noise ratio and ensures minimal disruption to the electric field distribution inside GIS. An experimental setup was established in a controlled laboratory environment to benchmark the multi-resonant sensor against the commercial UHF sensor. A 2.5-times enhancement of signal strength was observed. Since our sensor was implanted inside the GIS, a high signal-to-noise ratio (68.82 dB) was obtained. Moreover, we constructed a wireless calibration test to investigate the accuracy of the proposed sensor. The precision of the signal test was as high as 0.72 pC. The pulse phase distribution information was collected to demonstrate a phase-resolved partial discharge (PRPD) pattern. The experiment results validate the effectiveness of the proposed method and demonstrate excellent performance in PD detection.

Efficient and Shape-Sensitive Manipulation of Nanoparticles by Quasi-Bound States in the Continuum Modes in All-Dielectric Metasurfaces.

Current optical tweezering techniques are actively employed in the manipulation of nanoparticles, e.g., biomedical cells. However, there is still huge room for improving the efficiency of manipulating multiple nanoparticles of the same composition but different shapes. In this study, we designed an array of high-index all-dielectric disk antennas, each with an asymmetric open slot for such applications. Compared with the plasmonic counterparts, this all-dielectric metasurface has no dissipation loss and, thus, circumvents the Joule heating problem of plasmonic antennas. Furthermore, the asymmetry-induced excitation of quasi-bound states in continuum (QBIC) mode with a low-power intensity (1 mW/µm2) incidence imposes an optical gradient force of -0.31 pN on 8 nm radius nanospheres, which is four orders of magnitude stronger than that provided by the Fano resonance in plasmonic antenna arrays, and three orders of magnitude stronger than that by the Mie resonance in the same metasurface without any slot, respectively. This asymmetry also leads to the generation of large optical moments. At the QBIC resonance wavelength, a value of 88.3 pN-nm will act on the nanorods to generate a rotational force along the direction within the disk surface but perpendicular to the slot. This will allow only nanospheres but prevent the nanorods from accurately entering into the slots, realizing effective sieving between the nanoparticles of the two shapes.

Probing the anharmonicity of vibrational polaritons with double-quantum two-dimensional infrared spectroscopy

Abstract Strong coupling between the molecular vibrations and electromagnetic fields of light confined to an infrared cavity leads to the formation of vibro-polaritons – quasi-particles thought to provide the means to control the rates of chemical reactions inside a dark cavity. Despite the mechanisms indicating how vibrational coupling to the vacuum fields can affect the reaction rates are still not well understood, it has been recently demonstrated that the formation of the polariton states alters the ultrafast relaxation dynamics of the strongly coupled system. The relaxation dynamics in molecules, which is known to be important for the chemical reactivity, is directed by anharmonic couplings involving multiple intra- and inter-molecular vibrational degrees of freedom. However, the impact of the molecular anharmonicity on the polariton states remains elusive. Some theoretical models, employed to interpret the experimental observations, assume that vibrational polaritons are harmonic. Others assume a certain anharmonicity of vibro-polaritons; however, to date, it has not been experimentally determined. Herein, we performed double-quantum two-dimensional third-order nonlinear infrared spectroscopy of the carbonyl stretching (C=O) vibrational modes in a thin film of polymethyl methacrylate polymer (PMMA) strongly coupled to the surface lattice resonances of the periodic arrays of half-wavelength infrared disk antennas. We found that, indeed, the mechanical anharmonicity of polaritons is very small. Quantitatively, our results place an upper bound on a polariton mechanical anharmonicity of 2 cm−1, compared with that of the C=O mode in a PMMA film of 15 cm−1. Thus, our results support previous assumptions regarding the harmonic character of vibro-polaritons.

Influence analysis of director’s elements on the circular Yagi disc antenna performance at 1.8 GHz

<span lang="EN-US">This paper aims to investigate and design a Yagi disc antenna with a variable number of director elements for Band 3 in <a name="_Hlk139294022"></a>fourth-generation long term evolution (4G LTE) mobile applications. The array technique was introduced by increasing the number of director elements to achieve superior results and better performance, such as higher gain and lower return loss. Initially, the simulated results of return loss and gain with one director element were -19.02 dB and 8.51 dBi, respectively. Then, by increasing the number of directors to three and five elements, the antenna’s performance improved significantly from -32.44 to -42.68 dB for return loss and from 8.51 to 11.17 dBi for gain, respectively. The simulated circular Yagi disc antenna provided a response in the range of 1.78 to 1.82 GHz. Therefore, a model was fabricated and tested to validate the antenna design. The measured results matched well with the simulated ones. By increasing the number of director elements, the measurement results of gain and return loss at a frequency of 1.8 GHz also showed improvement from 7.70 to 11.09 dBi and from -27.31 to -32.91 dB, respectively. Meanwhile, the measured antenna provided a wider bandwidth in the range of 1.72-1.82 GHz.</span>

Design of Ka‐band, broadband, omnidirectional, with a top metal disk antenna

AbstractIn this report, a Ka‐band, broadband, omnidirectional, with a top metal disk antenna is proposed. The antenna is fed by an air waveguide. The TE10 mode of the waveguide can efficiently be converted into an air coaxial TEM mode by a compact waveguide air coaxial transition. After matching and adjusting, the dielectric substrate is loaded and then transited to the metal radiation structure loaded with a top metal disc to obtain omnidirectional electromagnetic waves efficiently converted to free space. By optimizing the sizes of waveguide to air‐coaxial transition structure and disk, and so on, a good broadband omnidirectional antenna performance is finally achieved. The measured fractional impedance bandwidth is larger than 30% with the reference of S11 dB, which fully verifies the rationality of the design. In addition, measured patterns at the plane of different azimuth angles almost coincide with each other, which shows an excellent omnidirectional pattern.

Simultaneous detection of molecules with the surface-enhanced infrared absorption sensor platform based on disk antennas with double spacer

Biomolecule detection has become important in many applications such as medical diagnosis, forensic analysis, basic biological studies, and food quality assessment. In particular, the Mid-infrared range offers an important opportunity for biomolecular sensing as it covers the molecular vibrational spectra of vital biochemicals such as Deoxyribonucleic acid, Ribonucleic Acid, and proteins. In this study, a double band absorbing plasmonic nanoantenna array with two gold disk resonators is proposed. The biosensing ability of this structure was investigated using the protein-goat anti-mouse immunoglobulin G model and Polymethyl methacrylate film. The basic structural bonds of protein monolayer, namely Amide-I, Amide-II, and Amide-III showed vibrational signatures at 6010 nm (∼1664 cm−1), 6496 nm (∼1539 cm−1), and 6989 nm (∼1431 cm−1) wavelengths, respectively. In addition, the spectral response of the proposed antenna structure was investigated using a Polymethyl methacrylate film by detecting the C=O and the C-H bonds. The strong dipole moment at C=O showed a strong absorption deep at 5782 nm (∼1730 cm−1) while the C-H bond has shown a relatively low absorption deep at 3350 nm (∼2985 cm−1) and 3395 nm (∼2946 cm−1). Our findings indicate that the double spacer disk configuration detects the spectral signature of the protein monolayer and Polymethyl methacrylate film in each band, simultaneously. The dual-band can be tuned independently by carefully engineering the radii of the double disks without making an effect on the other band. The proposed structure can be used as a characterization tool for identifying unknown complex molecules by simply detecting their spectral fingerprints in each mode of the dual-band, independently. Also, this design strategy can be insight to multi-mode SEIRA platforms, where more complex chemical molecules are needed to be detected or identified in biology, chemistry, and defense areas.

Improvement of Response Time and Heat-Transfer Capacity of Metamaterial Absorber for Terahertz Detector Applications

We have introduced a THz metamaterial absorber (MMA) system that consists of a metal disk antenna connected to successive dielectric and metal layers via a metal rod. The heat-transfer speed and capacity of the proposed platform with a metal rod inserted through the dielectric layer have been numerically studied for the first time in this work. The proposed THz MMA system can improve the heat-transfer capacity of 0.7 K/s compared to without a metal rod situation. The simulation proves that heat transfer can be achieved in the proposed absorber less than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10 ~\mu \text{s}$ </tex-math></inline-formula> times compared to without a metal rod case. The simulation results indicate that the absorption strength of the MMA is almost independent of the rod depth. This detector system will be remarkably beneficial for imaging applications where fast heat-signal conversion is necessary.

Size Optimization of Disk Antenna for 5-cm ECR Ion Thruster

Size Optimization of Disk Antenna for 5-cm ECR Ion Thruster

Nanostructured In3SbTe2 antennas enable switching from sharp dielectric to broad plasmonic resonances

Abstract Phase-change materials (PCMs) allow for non-volatile resonance tuning of nanophotonic components. Upon switching, they offer a large dielectric contrast between their amorphous and crystalline phases. The recently introduced “plasmonic PCM” In3SbTe2 (IST) additionally features in its crystalline phase a sign change of its permittivity over a broad infrared spectral range. While optical resonance switching in unpatterned IST thin films has been investigated before, nanostructured IST antennas have not been studied, yet. Here, we present numerical and experimental investigations of nanostructured IST rod and disk antennas. By crystallizing the IST with microsecond laser pulses, we switched individual antennas from narrow dielectric to broad plasmonic resonances. For the rod antennas, we demonstrated a resonance shift of up to 1.2 µm (twice the resonance width), allowing on/off switching of plasmonic resonances with a contrast ratio of 2.7. With the disk antennas, we realized an increase of the resonance width by more than 800% from 0.24 µm to 1.98 µm while keeping the resonance wavelength constant. Further, we demonstrated intermediate switching states by tuning the crystallization depth within the resonators. Our work empowers future design concepts for nanophotonic applications like active spectral filters, tunable absorbers, and switchable flat optics.

Optimization of microwave circular-view disc antenna design for sensors containing transceivers

Optimization of microwave circular-view disc antenna design for sensors containing transceivers

Herbicide/pesticide sensing with metamaterial absorber in THz regime

Terahertz (THz) technology has been attracted great interest in many research areas over the years, especially THz plasmonics for sensing applications since intra- and inter-molecular vibrations are within the THz range. The sensitivity of free-space THz detection can be boosted up by use of metamaterials (MM), which are artificial structures in subwavelength scale of the incident light. These artificial materials present high electric field enhancement and high sensitivity to the change in their surroundings. In this article, residual herbicides/pesticides have been investigated both theoretically and experimentally with a polarization-insensitive THz metamaterial absorber (MMA) composed of dielectric-metal disk antennas. Our THz MMA can detect as small as 5 ppM of commonly used herbicide/pesticide, namely paraquat and glyphosate. The results show that sensitivity is greatly improved by using THz MMA, with the limit of detection (LOD) of these herbicides/pesticides reaching to 5 ppM. These results indicate that THz MMA platform could be a valuable method for highly sensitive THz applications in food quality and safety control. We believe, our sensor platform based on general c-mos technology fabrication could be a potential detection tool for herbicides/ pesticides residues in agriculture and food products.

A Floating Octave Bandwidth Cone-Disk Antenna for Detection of Cosmic Dawn

The critical component of radio astronomy radiometers built to detect redshifted 21-cm signals from Cosmic Dawn is the antenna element. We describe the design and performance of an octave bandwidth cone disc antenna built to detect this signal in the band 40 to 90 MHz. The Cosmic Dawn signal is predicted to be a wideband spectral feature orders of magnitude weaker than sky and ground radio brightness. Thus, the engineering challenge is to design an antenna at low frequencies that is able to provide with high fidelity the faint cosmological signal, along with foreground sky, to the receiver. The antenna characteristics must not compromise detection by imprinting any confusing spectral features on the celestial radiation, ground emission or receiver noise. An innovation in the present design is making the antenna electrically smaller than half wavelength and operating it on the surface of a sufficiently large water body. The homogeneous and high permittivity medium beneath the small cone-disc antenna results in an achromatic beam pattern, high radiation efficiency and minimum unwanted confusing spectral features. The antenna design was optimized in WIPL-D and FEKO. A prototype was constructed and deployed on a lake to validate its performance with field measurements. Index Terms: Antenna measurements, radio astronomy, reflector antennas.

Implementation of a unidirectional-mode ferrite disk antenna using permanent magnets and a two-stage matching network

We experimentally demonstrate a circularly polarized antenna that utilizes unidirectional surface waves that propagate on the boundary of a small ferrite disk. The ferrite disk is metalized on top and is mounted on a grounded dielectric substrate. The disk is normally biased by a magnetic field that is provided by two permanent magnets below and above the structure. A two-section feeding network is used to feed the antenna. The operation frequency of the antenna can be adjusted by changing the magnitude of the applied magnetic bias. The sense of polarization can be reversed by reversing the direction of the applied bias.

Present Situation and Development of Internal Sensors for Ultra-high Frequency Detection in Gas Insulated Switchgear

This paper discusses the application situation of the ultra-high frequency (UHF) method and optical method in the detection of partial discharge of gas insulated switchgear (GIS), and the differences between external and internal UHF sensors. The sensor is a key technology in the PD detection method, and its performance directly affects the validity of the monitoring results. Different partial discharge detection sensors have different characteristics and working environments. UHF sensor has the advantages of wide detection range and convenient layout. Optical sensors have the advantages of high sensitivity and fast response speed. Six main types of internal sensors are evaluated and the performance indicators of internal sensors are discussed which includes disc antenna, loop antenna, dipole antenna, planar spiral antenna, conical antenna, photoelectric composite sensor. Furthermore, some problems need to be solved are proposed for further research, which is of great significance to the safe and stable operation of power equipment.

A Dual-Wideband Crossed Elliptical Disc Antenna with Reconfigurable Radiation Patterns for Multiband Applications

Wydawnictwo SIGMA-NOT wydaje czasopisma fachowe informujące swoich czytelników o najnowszych osiągnięciach naukowych i nowoczesnych rozwiązaniach technicznych w Polsce i na świecie, popularyzuje problemy techniczne oraz poszerza wiedzę i kulturę techniczną.

Method of analytical regularization in the analysis of axially symmetric excitation of imperfect circular disk antennas

This work presents accurate numerical method and computational results in the modeling of the axisymmetric radiation of resistive and thin-dielectric circular disk-on-substrate antennas. To simulate resistive and thin-dielectric disk features, we use two-side Generalized Boundary Conditions (GBC). The analysis is based on the singular integral equations (IEs) and the Method of Analytical Regularization (MAR) exploiting a Galerkin Method (GM) with judicious basis functions, which convert IEs into the Fredholm second-kind infinite matrix equations. Unlike previously known numerical techniques, this guarantees convergence and enables us to compute the solution with controlled accuracy even in sharp resonances. Numerical results demonstrate the effect of disk losses and transparency on the fundamental radiation phenomena and help improve antenna characteristics such as radiation efficiency.

Design of phase coded spiral resonator based Chipless RFID tag for tracking applications

RFID (Radio identification) is a technology which deals with the wireless identification of people and products. This chipless RFID tag design is on research to replace chipped RFID tags, which employs high cost silicon wafer to store unique identification code. The main challenge in the design of chipless RFID tag is how to encode the data without a chip. This challenge is overcome by the use of electromagnetic properties of the resonators, filters etc to encode the data bits. In this work RFID tag is designed based on multiresonators with each resonator representing a data bit. The proposed tag consists of the multiresonating circuit to store information bits and transmitting and receiving UWB antenna for wireless communication with the RFID reader for identification. The multiresonating circuit designed consists of 4-spiral resonators electromagnetically coupled to the microstip coupled line. Each spiral resonates at unique resonating frequency representing the unique data bit. The data encoding is carried out with the help of phase ripples at the resonating frequency of the spirals. Three variations are observed and corresponding 3-logic states (0, 1, 2) are encoded. The designed tag is simulated in Advanced Design System (ADS) using RO-4003 substrate with the dielectric constant 3.38 and thickness of 20 mil. From the proposed methodology, a total of 34=81 unique tags can be designed that can be employed in cheap item tracking. The Monopole disc antenna is designed which operates for wide band covering all resonating frequency of the spiral resonator.

Analytical calculation for input impedance of a circularly‐polarized ferrite disk antenna including higher order modes

We propose an accurate analytical model for a circularly polarized antenna comprising a normally magnetized, grounded ferrite disk with a metalized top surface. The antenna is assumed to be excited by a conventional current probe. In the case of a thin ferrite disk, the electromagnetic fields of the dominant mode of the antenna do not vary in the direction normal to the disk. However, with increasing thickness of the ferrite disk, higher order modes start to affect antenna characteristics such as resonance frequency. This work presents an analysis of the structure that takes into account all higher modes of the antenna. To validate the theoretical calculations, HFSS simulations are performed. The antenna can be tuned by changing the magnetic bias field.

Wideband or Dual-Band Low-Profile Circular Patch Antenna With High-Gain and Sidelobe Suppression

This communication presents a wideband or dual-band circular disk antenna with high-gain and sidelobe suppression (SLS). The antenna has a single layer and single-fed configuration. The antenna can operate with the radiation field superposition of TM12 and TM14 modes at one frequency, which provides high-gain and SLS. A circle of 10 shorting vias with nonidentical diameters are loaded inside the antenna cavity in order to excite the field superposition of TM11 and TM13 modes at another frequency. By modifying the radius of the vias, the resonant frequency with the TM11 and TM13 superposition can be tuned closer to or further away from the one with the TM12 and TM14 superposition. In this way, a wideband or dual-band behavior can be obtained with high-gain and SLS. The proposed antenna achieves the impedance bandwidth of 6.46% for the wideband case, which is over 6 times wider than the previous literature. In the dual-band case, the bandwidth is 1.48% and 1.61% at each band. For both cases, the gain and the SLS are higher than 15 dBi and 10 dB within the operating bands, respectively. Measurements are carried out with prototypes and agree well with simulations.

Disc Antenna Enhanced Infrared Spectroscopy: From Self-Assembled Monolayers to Membrane Proteins.

Plasmonic surfaces have emerged as a powerful platform for biomolecular sensing applications and can be designed to optimize the plasmonic resonance for probing molecular vibrations at utmost sensitivity. Here, we present a facile procedure to generate metallic microdisc antenna arrays that are employed in surface-enhanced infrared absorption (SEIRA) spectroscopy of biomolecules. Transmission electron microscopy (TEM) grids are used as shadow mask deployed during physical vapor deposition of gold. The resulting disc-shaped antennas exhibit enhancement factors of the vibrational bands of 4 × 104 giving rise to a detection limit <1 femtomol (10-15 mol) of molecules. Surface-bound monolayers of 4-mercaptobenzoic acid show polyelectrolyte behavior when titrated with cations in the aqueous medium. Conformational rigidity of the self-assembled monolayer is validated by density functional theory calculations. The membrane protein sensory rhodopsin II is tethered to the disc antenna arrays and is fully functional as inferred from the light-induced SEIRA difference spectra. As an advance to previous studies, the accessible frequency range is improved and extended into the fingerprint region.