Asymmetric Dipole Research Articles

High-Q triple-mode quasi-bound states in the continuum in an asymmetric dielectric metamaterial

Bound states in the continuum (BICs) in metamaterials have attracted much attention due to their high efficiency in field enhancing. In this paper, we numerically demonstrated the triple-mode symmetry-protected BICs (SP-BICs) in an all-dielectric microtube metamaterial. By moving the hollows transversely and longitudinally in microtubes, three SP-BICs are transformed into high quality-factor (Q-factor) quasi-BICs (q-BICs), which are supported by asymmetric magnetic toroidal dipole electric hexapolar resonances respectively. The maximum Q-factor of q-BICs enabled by asymmetric magnetic toroidal dipole reaches 67647. This high Q-factor triple-mode q-BICs in all-dielectric microtube metamaterial has great potential in the applications of sensing, laser generation, and nonlinear optics.

Dipole Orientation Engineering in Crosslinking Polymer Blends for High-Temperature Energy Storage Applications.

Polymer dielectrics that perform efficiently under harsh electrification conditions are critical elements of advanced electronic and power systems. However, developing polymer dielectrics capable of reliably withstanding harsh temperatures and electric fields remains a fundamental challenge, requiring a delicate balance in dielectric constant (K), breakdown strength (Eb), and thermal parameters. Here, amide crosslinking networks into cyano polymers is introduced, forming asymmetric dipole pairs with differing dipole moments. This strategy weakens the original electrostatic interactions between dipoles, thereby reducing the dipole orientation barriers of cyano groups, achieving dipole activation while suppressing polarization losses. The resulting styrene-acrylonitrile/crosslinking styrene-maleic anhydride (SAN/CSMA) blends exhibit a K of 4.35 and an Eb of 670 MV m-1 simultaneously at 120°C, and ultrahigh discharged energy densities (Ue) with 90% efficiency of 8.6 and 7.4 J cm-3 at 120 and 150°C are achieved, respectively, more than ten times that of the original dielectric at the same conditions. The SAN/CSMA blends show excellent cyclic stability in harsh conditions. Combining the results with SAN/CSMA and ABS (acrylonitrile-butadiene-styrene copolymer)/CSMA blends, it is demonstrated that this novel strategy can meet the demands of high-performing dielectric polymers at elevated temperatures.

“Gear-like” process between asymmetric dipole eddies from satellite altimetry

Mesoscale dipoles compose two counter-rotating mesoscale eddies. They are observed in oceans worldwide and significantly impact the biogeochemical cycle, marine ecosystems, and ocean water transport. This study investigates the evolution of asymmetric dipole eddies based on the satellite altimeter data for the period January 1993–December 2020. The coupling and decoupling of eddy dipoles impact various eddy properties. When the movement of eddies has a dipolar structure, a gentle convergence in parameters (rotational speed, amplitude, eddy kinetic energy, propagation speed, and advective nonlinearity) between the asymmetric dipole eddies is observed–this study refers to it as the “gear-like” process. Kinematic characteristics further indicate that the stronger dipole eddies generally drive the weaker ones to revolve during the “gear-like” process. The revolution direction remains consistent with the rotation direction of stronger dipole eddies. Additionally, eddy size remains relatively stable during the “gear-like” process. The composites of sea level anomaly (SLA) demonstrate that dipole eddies are compressed into a kidney-like shape along the line through their centers. This shape is confirmed by the composites of sea surface temperature anomalies, which closely correspond to the structure of SLA. These findings augment the knowledge regarding the evolution of asymmetric dipole eddies and provide a novel perspective for studying dipoles and eddy-eddy interactions.

Asymmetric Dipole Trends in Geodynamo Models and the Paleomagnetic Field

AbstractTemporal trends in the paleomagnetic dipole moment exhibit the property of positive skewness. On average, positive trends are larger and occur less frequently than negative trends over timescales of several tens of kyr. We explore the origin of this property using numerical geodynamo models. A suite of models reveals that skewness arises for a restricted set of boundary conditions. Models driven by heat flow at the top and bottom boundaries exhibit very little skewness, whereas models driven solely by heat flow on the lower boundary produce significant positive skewness. Further increases in skewness occur in the presence of thermal stratification at the top of the core. The level of skewness in the geodynamo models is correlated with estimates of upwelling near the core‐mantle boundary. Sustained upwelling is expected to increase magnetic‐flux expulsion, contributing to higher levels of skewness. Similar behavior is recovered from stochastic models in which the dipole is generated by a random series of cyclonic convection events. Skewness in the stochastic models is quantitatively similar to estimates from the geodynamo models when the average recurrence time of the convection events is 100 years. Extending the stochastic models to the paleomagnetic field implies a longer recurrence time of 1,000 years or more. We interpret this recurrence time in terms of the timing of flux‐expulsion events rather than individual convective events. Abrupt increases in the dipole moment from flux expulsion can produce skewed trends on timescales of tens of kyr.

Miniaturized Polarization-Insensitive Rectifying Metasurface for Powering Internet of Things Devices

In this paper, a miniaturized polarization-insensitive rectifying metasurface unit cell is proposed for powering electric devices of Internet-of-Things (IoT). The metasurface, an array of periodic unit cells, consists of two layers of substrate and three layers of metal. The metasurface unit cell is composed of eight asymmetric dipoles, which are arranged orthogonally and closely on both surfaces of the upper substrate. The strong coupling between dipoles induces extra reactive components, which makes the unit size be miniaturized to only 0.15 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> . The miniaturization mechanism is analyzed by the equivalent circuit theory. The simulation results show that the harvesting efficiency for arbitrary polarized waves are higher than 90% from 2.2 to 2.7 GHz (20%). Being integrated with Schottky diodes at the proper position, the rectifying metasurface is designed. A 2 × 2 array with the size of 0.3 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.3 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> was fabricated and measured. The maximum harvesting-rectifying efficiency is 61% at 2.45 GHz under different polarization angles. When the power density is 8 mW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , 80 mW direct current (DC) power could be obtained.

Dual-band circularly polarized asymmetric dipole array antenna for GPS L1 and L2 bands

A dual-band, circularly polarized (CP) asymmetric dipole array antenna for Global Positioning System (GPS) applications with a wide beam is presented in this paper. The proposed antenna comprises two different-sized printed crossed dipoles with integrated baluns fed by an asymmetric feeding network to achieve dual-band functionality. Using two branch-line couplers with different dimensions in the feeding network performs Right-Hand Circular Polarization (RHCP) operation at GPS L1 and L2 bands. According to the experiments, the proposed antenna has wide impedance bandwidths of 24.82% (1139.5–1462.4 MHz) and 14.82% (1500.4–1740.5 MHz), and 3 dB Axial-Ratio (AR) bandwidth of 37.4% (1132.3–1653.2 MHz) to cover the GPS L1 and L2 bands. Furthermore, at 1227 MHz frequency, the antenna has a gain of 4.65 dBic, and a 3 dB AR beamwidth of 148.2° facing the sky. Also, at 1575 MHz frequency, a gain of 5.25 dBic and a 3 dB AR beamwidth of 139.3° are achieved.

Terahertz all-dielectric metasurface sensor based on quasi-bound states in the continuum.

We proposed a quasi-bound states in the continuum (QBICs) metasurface to realize sensing in the terahertz band. It consists of silicon split ellipse cylinders with different short-long axes and a quartz substrate. By introducing two asymmetric split ellipse cylinders unit cells, magnetic dipole and electric quadrupole resonances of the proposed structure are investigated by multiple Pole theory. This shows that the continuum bound states are transformed into quasi-BICs by tuning the length of the ellipse long axis, and so a high-quality factor can be obtained. The Q value of the proposed structure is 3205, and the figure of merit is 469.64. It has potential applications in gas, liquid, and biomaterial sensing.

Short Asymmetrical Inductive Dipole Antenna for Direct Matching to High-Q Chips

A planar antenna structure based on a folded asymmetrical dipole is presented, whose geometrical parameters are seen to independently determine either the real or the imaginary parts of the complex radiation impedance. This unique feature allows very efficient and wideband conjugate matching coupling to nonconventional RF sources of arbitrary internal impedance, i.e., small resistance with large and negative reactance. The antenna theoretical framework is developed and an optimized design to match a photodiode is manufactured and measured. The results show a fractional bandwidth of about 20% in the 28 GHz band.

Coexistence of circular dichroism and asymmetric transmission in Babinet-complementary metamaterials.

Chiral metamaterials with circular dichroism (CD) or asymmetric transmission (AT) draw enormous attention for their attractive applications in polarization transformers, circular polarizers, and biosensing. In this study, a feasible trilayer chiral metamaterials (TCM) is designed and investigated in theory and simulation. The proposed TCM is composed of a nanoslit layer and a Babinet-complementary nanorod layer separated by a nanoslit spacer. Owing to symmetry breaking by the tilted nanoslit in metal film, the TCM shows simultaneous CD and AT effects in the near-infrared region. The simulated electric charge distributions prove that the chirality arises from the excitation of asymmetric electric dipole resonant modes due to the coupling of adjacent unit cells. Moreover, CD and AT can be tuned by the tilted angle of the nanoslit and the thickness of the spacer, the fitting functions of which are consistent with the theoretical formulas based on transmittance matrix analysis. The proposed nanostructure offers a potential strategy for manipulating metamaterials with simultaneous CD and AT effects, allowing a multitude of exciting applications such as ultra-sensitive polarization transformer and biosensor.

An Ultrawideband Printed Monopole Antenna Analyzed with the Theory of Characteristic Modes

In this paper, the analysis of an UWB monopole antenna using the Theory of Characteristic Modes is presented. It starts from the modal study of an asymmetric dipole (structure 1), and then complements and compares it with a broadband monopole (structure 2), aiming to understand the operation principle of the proposed antenna. To achieve this, the electromagnetic properties of the structures are analyzed through the generation of its characteristic angles, modal radiation patterns, characteristic currents, and the power contribution percentage of each mode to the total radiated power, providing a vision on how the superposition of individual characteristic modes enables UWB operation. The prototype model is fabricated, and the measured results agree very well with the full-wave simulations results. The proposed prototype has a very low profile and operates in the frequency band from 2.8 GHz to exceed 10 GHz for a reflection coefficient S11 less than -10dB.

Asymmetrical and symmetrical naphthalene monoimide fused perylene diimide acceptors for organic solar cells

Perylene diimide (PDI) and its derivatives have received intensive research attention due to their promising applications in organic electronics, such as organic solar cells (OSCs) and organic field-effect transistors (OFETs). Fusing PDI with other arene imide is a robust strategy for the construction of high performance n-type organic semiconductors. In this work, we report two PDI derivatives (asymmetrical FPN and symmetrical FNPN) by fusing naphthalene monoimide (NMI) moieties at the bay regions. The optoelectronic characteristics of FPN and FNPN have been investigated. Using PBDB-T as donor material, FPN and FNPN based OSCs provide optimal power conversion efficiency (PCE) of 3.13% and 1.79%, respectively. The higher PCE of FPN based OSCs may be ascribed to the asymmetrical configuration-induced large natural dipole moment and the reinforced intermolecular forces, suggesting that the introduction of asymmetric structure is an effective strategy to improve the photovoltaic performance of PDI based OSCs.

Design of a high-efficiency thin-type metasurface hologram

To improve the imaging efficiency and reduce profile, a high efficiency, thin-type metasurface hologram based on induced magnetism is proposed. Both types of units consist of two asymmetric electric dipole elements printed on a thin-type dielectric substrate with only 1.3 mm thickness (λ 0/6.4 at 36 GHz). By tuning the magnetic and electric responses, the transmitting phase of the units can be changed. Both types of units are designed to cover the quantized 2π phase range with the transmittance above 90%. Based on holographic theory, the target image field distribution and the incident plane wave can be regarded as object wave and reference wave respectively. A holographic metasurface is designed to record phase information of the target image. The simulation and experiment show that the designed metasurface can reproduce a clear image with a 65.86% imaging efficiency, which provides a new way to realize high-efficiency holographic imaging.

Decadal Variability of Winter Warm Arctic‐Cold Eurasia Dipole Patterns Modulated by Pacific Decadal Oscillation and Atlantic Multidecadal Oscillation

AbstractIn recent decades, the winter surface air temperature (SAT) anomaly in the Northern Hemisphere has exhibited a warm Arctic‐cold Eurasia (WACE) dipole pattern and this has undergone significant decadal variation. In this paper, the physical cause of the decadal variability of the WACE pattern is explored, and it is shown to be mediated by the phases of the Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO). Although the negative PDO (PDO−) or positive AMO (AMO+) favors the WACE pattern, the meridional structure of the pattern is significantly influenced by whether PDO− or AMO+ dominates. During PDO− (AMO+) phase, the winter‐mean WACE pattern shows an asymmetric dipole with weak (strong) warm anomaly over the Barents‐Kara Seas or BKS and strong (weak) cold anomaly over central Eurasia or Siberia, which corresponds to Ural blocking (UB) concurring with the negative (positive) phase of North Atlantic Oscillation in a winter‐mean field. The winter asymmetric WACE pattern is more strongly related to PDO− than AMO+. It is further found that an asymmetric sub‐seasonal WACE dipole pattern with strong (weak) warm anomaly over BKS and weak (strong) cold anomaly over Siberia is usually formed during the UB episode due to favored (suppressed) sub‐seasonal downward infrared radiation and turbulent heat flux over BKS during AMO+ (PDO−), which leads to a strong asymmetric dipole of the winter WACE pattern.

A Compact Wideband Dual-Polarized Base Station Antenna Using Asymmetric Dipole

A compact wideband dual-polarized antenna for base station application is proposed. The antenna element consists of a main radiator, two baluns, and a reflector. Two methods are used to enhance bandwidth and improve the port-to-port isolation. Firstly, by integrating the parasitic elements to traditional dipoles, new resonant modes are introduced to realize broadband, which can be controlled flexibly. Subsequently, part of the parasitic elements is removed to form asymmetric dipoles. Due to the asymmetry construction of the design, the polarization isolation of the antenna achieves more than 30 dB in the whole working band with stable radiation patterns. In addition, the specially designed parasitic elements achieve enhanced bandwidth without increasing the size of the radiator. The Simulation and measurement results show that the antenna has an impedance bandwidth of 32.7&#x0025; (690-960 MHz). Moreover, a stable half-power beamwidth (HPBW) of 68&#x00B0;&#x00B1;5&#x00B0; and a high gain of 8.5&#x00B1;0.3 dBi is achieved. To verify the performance of the antenna, a compact high-gain base station array was designed and manufactured. The good performance of the proposed antenna makes it a promising candidate for 4G/5G base station application.

Asymmetrical dipole antenna based on a phase-correcting dielectric lens

Problem. Modern mobile robotic systems are increasingly used in various fields of human activity. More and more stringent requirements are imposed on them to ensure high throughput, broadband and reliability of data transmission and control channels at the maximum distance from the control center. And what I would like to note separately is the requirement to reduce the cost of such complexes as much as possible. Therefore, the development of technologically advanced, economically feasible antenna systems that provide an increase in the energy potential of the radio channel in the interval of the robotic complex - control point is one of the ways to solve this problem. Formulation of the problem. It is required to develop a mechanically strong, technological antenna, built on the basis of lens structures of various configurations, made of modern dielectric materials, characterized by reduced weight and size characteristics and cost price, which will increase the level of radiated electromagnetic energy in a wide frequency band. Purpose of the article. Present the developed model of an asymmetric dipole antenna and the results of a numerical experiment. Result. The antenna design is made on a metallized round substrate and is a polystyrene cylinder with a funnel-shaped hole, inside which there is an asymmetrical conical vibrator arm. The results of calculations showed that in the frequency band, which is used to organize direct broadband radio communication channels with robotic complexes, the gain varies within 5.5-9 dB, which is superior in this parameter to the commonly used whip antennas. The calculated standing wave ratio confirms the performance of the developed antenna model in a wide frequency band. The impedance response and the Smith-Smith diagram showed a preliminary calculated spread of the input impedance of the antenna from 30 to 95 ohms. Practical significance. The proposed antenna model ensures manufacturability, mechanical strength, and low cost. The full-azimuth radiation mode and increased gain make it possible to predict the possibility of using this antenna as part of the equipment for the data transmission channel and control of robotic complexes such as unmanned aerial vehicles.

Microfluidic Biosensor for Rapid Nucleic Acid Quantitation Based on Hyperspectral Interferometric Amplicon-Complex Analysis.

Nucleic acid detection plays a vital role in both biomedical research and clinical medicine. The temperature circulation changes of the widely used polymerase chain reaction technique are time-consuming and technically challenging for system development. Recombinase polymerase amplification (RPA) is an isothermal method for rapid nucleic acid detection. However, current RPA amplicon detection methods are complicated and expensive and easily generate false positives, restricting the promotion of RPA techniques. In this work, a hyperspectral interferometric amplicon-complex quantitation method is presented, combined with asymmetric dipole complex strategy optical scattering analysis. GelRed dye was utilized to form amplicon-complex particles, and the Fourier domain spectrum computation contributed to complex scattering quantitation. With this method, a supporting microfluidic chip and automatic system were developed to achieve integrated, rapid, quantitative, and miniscule nucleic acid detection. The Plasmodium falciparumdhfr gene was utilized as an example for targeted nucleic acid quantitation and single nucleotide polymorphism detection. The total reaction time was decreased to merely 20 min, and the limit of detection was only 3.17 ng/μL. The minimum measurable concentration of target was 1.68 copies/μL, 31.67 times more sensitive than turbidity detection, and the single reaction chamber was only 9.33 μL. No scattering increase occurred for template-free control, and thus, false positives caused by primer dimers and nonspecific products could be avoided. The experimental results prove that the provided method and system can detect single-base mutations in the dhfr gene and is a reasonable technique for rapid, automatic, and low-cost nucleic acid detection.

Fully integrated wideband phased array with large scan range and 5:1 bandwidth

In this work, a fully integrated phased array using multi-layer printed circuit board (PCB) fabrication technologies is presented. This array is directly fed by 50 Ω coaxial cables, without balanced-to-unbalanced transitions. An asymmetric dipole is used to achieve stable input impedance. Furthermore, to broaden the operating bandwidth, a coupling patch is designed beneath the asymmetric dipole , which also eliminates the common-mode resonance and decreases the array profile. In addition, three wide-angle impedance matching (WAIM) layers with different structures are utilised to improve the scan range in all scanning planes. Infinite array simulations indicate that the proposed array can operate over a 5.1:1 bandwidth (2.4 ∼ 12.2 GHz) with an active voltage standing wave ratio below 3 while scanning up to ± 60° in H plane and ±75° in the E plane. Furthermore, the proposed antenna, whose cross-polarization levels remain below −35 and −7.5 dB when scanning up to 75° in the E plane and 60° in the D plane, demonstrates the merits of high polarization purity. Array simulations are verified by the measurements of a 12 × 12 prototype, and good agreement is observed.

Nearly spherical ablation zone with minimally invasive microwave ablation: Analysis and experimental characterization of a tapered-tip symmetric dipole antenna

Microwave ablation (MWA) is a widely used technology for tumors treatments. The reported asymmetric dipole antennas were not ideal in ablation zone. Although some methods were proposed to improve the ablation performance, other important characteristics were still not satisfactory enough, such as poor impedance matching, increased invasion diameter, or additional insertion devices. In this paper, a minimally invasive antenna with a nearly spherical ablation zone for microwave ablation is presented by a tapered-tip symmetric dipole structure with a sleeve. The tapered-tip symmetric dipole, fed by a coaxial line, are composed of a tapered-tip cylinder arm and a hollow cylinder arm. Both of the lengths of the two arms are approximately equal to a quarter of wavelength. The proposed antenna provides good matching at resonating frequency without any extra impedance matching network. Moreover, the tapered-tip structure enables the proposed MWA antenna be inserted into the tissues directly without an additional needle-shape catheter. Furthermore, the sleeve structure, electrically isolated from the dipole and the coaxial feed line, is employed to prevent the current and thermal from flowing along the feed line. A minimally invasive antenna with a diameter of only 1.9 mm working at 2.45 GHz is designed and fabricated for verification, in which different input power and heating time are taken into account. The temperature evolution in four locations of the liver tissue is recorded by using a 4-channel temperature monitoring system. The comparison with a commercial MWA antenna of the same diameter is also included. Simulation and experiment results show that the proposed MWA antenna create nearly spherical ablation zones. The proposed MWA antenna would be promising for minimally invasive medical applications.

A Nonlinear Multiscale Theory of Atmospheric Blocking: Structure and Evolution of Blocking Linked to Meridional and Vertical Structures of Storm Tracks

AbstractThis paper examines the impact of the meridional and vertical structures of a preexisting upstream storm track (PUST) organized by preexisting synoptic-scale eddies on eddy-driven blocking in a nonlinear multiscale interaction model. In this model, the blocking is assumed, based on observations, to be comprised of barotropic and first baroclinic modes, whereas the PUST consists of barotropic, first baroclinic, and second baroclinic modes. It is found that the nonlinearity (dispersion) of blocking is intensified (weakened) with increasing amplitude of the first baroclinic mode of the blocking itself. The blocking tends to be long lived in this case. The lifetime and strength of blocking are significantly influenced by the amplitude of the first baroclinic mode of blocking for given basic westerly winds (BWWs), whereas its spatial pattern and evolution are also affected by the meridional and vertical structures of the PUST. It is shown that the blocking mainly results from the transient eddy forcing induced by the barotropic and first baroclinic modes of PUST, whereas its second baroclinic mode contributes little to the transient eddy forcing. When the PUST shifts northward, eddy-driven blocking shows an asymmetric dipole structure with a strong anticyclone–weak cyclone in a uniform BWW, which induces northward-intensified westerly jet and storm-track anomalies mainly on the north side of blocking. However, when the PUST has no meridional shift and is mainly located in the upper troposphere, a north–south antisymmetric dipole blocking and an intensified split jet with maximum amplitude in the upper troposphere form easily for vertically varying BWWs without meridional shear.

Comparison of 16-Channel Asymmetric Sleeve Antenna and Dipole Antenna Transceiver Arrays at 10.5 Tesla MRI.

Multi-element transmit arrays with low peak 10 g specific absorption rate (SAR) and high SAR efficiency (defined as are essential for ultra-high field (UHF) magnetic resonance imaging (MRI) applications. Recently, the adaptation of dipole antennas used as MRI coil elements in multi-channel arrays has provided the community with a technological solution capable of producing uniform images and low SAR efficiency at these high field strengths. However, human head-sized arrays consisting of dipole elements have a practical limitation to the number of channels that can be used due to radiofrequency (RF) coupling between the antenna elements, as well as, the coaxial cables necessary to connect them. Here we suggest an asymmetric sleeve antenna as an alternative to the dipole antenna. When used in an array as MRI coil elements, the asymmetric sleeve antenna can generate reduced peak 10 g SAR and improved SAR efficiency. To demonstrate the advantages of an array consisting of our suggested design, we compared various performance metrics produced by 16-channel arrays of asymmetric sleeve antennas and dipole antennas with the same dimensions. Comparison data were produced on a phantom in electromagnetic (EM) simulations and verified with experiments at 10.5 Tesla (T). The results produced by the 16-channel asymmetric sleeve antenna array demonstrated 28 % lower peak 10 g SAR and 18.6 % higher SAR efficiency when compared to the 16-channel dipole antenna array.