Unambiguous Manifold Analysis of Spatially Spread Dual-Polarized Dipole Array

ABSTRACT In this paper, a millimeter wave (mmW) broadband circularly polarized (CP) magnetoelectric (ME) dipole antenna array loaded with serrated branches is proposed. The array achieves wide impedance bandwidth (IBW), broad axial ratio bandwidth (ARBW), and stable gain across the entire overlapping bandwidth (BW) of IBW and ARBW. The antenna structure comprises three dielectric layers, two pairs of ME dipoles, and an easy-to-integrate feed network formed by Z-shaped slot-coupled microstrip lines. The axial ratio (AR) of the antenna is significantly reduced by loading serrated branches onto the electric dipole, and excellent CP performance is achieved through structural slotting and angular truncation design. Simulation results demonstrate that the ARBW of the antenna element reaches 31.7% (36.9–50.8 GHz) and an IBW of 51.1% (30–50.6 GHz), with gain exceeding 5 dBic across the entire IBW. To enhance gain performance, a 4 × 4 antenna array is designed and fabricated. Measurements demonstrate an ARBW of 43% (30.6–47.4 GHz) and an IBW of 54.8% (27.9–49 GHz). The peak gain attains 17.8 dBic, with gain exceeding 16 dBic across the overlapping BW. Cross-polarization levels remain lower than −20 dB in both xoz- and yoz-planes, while the radiation efficiency surpasses 79% in the overlapping BW, with an average of 85%.

ABSTRACT In this letter, a low scattering ultrawideband tightly coupled dipole array (TCDA) based on the wideband absorber is proposed in this paper. The absorber consists of I‐shaped metal strips loaded with resistors. Transverse metal strips are attached at both ends of the vertical strips to enhance the capacitive coupling between neighboring I‐shaped strips, resulting in a broader low‐frequency absorption bandwidth. The feeding networks and wide‐angle impedance matching (WAIM) layers are meticulously designed to achieve optimal impedance matching and scanning performance. A 10×10 array prototype is fabricated and measured. Simulation and experimental results show that the designed array achieves 108.6% relative bandwidth of at least 10 dB scattering cross section reduction, demonstrating improvement over existing solutions. The array can scan up to 70° in the E‐plane and 60° in the H‐plane for voltage standing wave ratio (VSWR) < 3.5, exhibiting high potential for large beam scanning.

A key aspect in the design of mixed polar-organic layers and metallic or semiconducting devices is the dielectric constant of the organic aggregate, which modulates the surface work function and band alignments. In simple electrostatic models, a monolayer is treated as an array of point dipoles whose depolarization depends only on an effective molecular polarizability. However, the absence of a unified framework in quantum-chemical computational studies leaves the reliability of the point dipole model uncertain. In this work, we demonstrate the breakdown of the point dipole approximation for highly packed aggregates and propose an alternative heuristic model that relies on a second molecular parameter: the molecular size. The performance of this approach is validated through comparison with computational methods based on Density Functional Theory (DFT) and second-order Møller-Plesset perturbation theory (MP2) calculations. Our extended dipole model provides robust estimates of depolarization effects, offering a rapid prescreening tool for selecting polar organic candidates in surface functionalization.

This study focuses on the joint estimation of the direction of departure (DOD) and direction of arrival (DOA) of multiple targets in bistatic multiple input multiple output (MIMO) radar systems employing orthogonal waveforms. A linear array of half-wavelength dipole antennas (HWD) with known mutual coupling is utilized. The proposed method applies a two-dimensional Capon (2D Capon) algorithm to estimate both the DOD and DOA of multiple targets. To mitigate the adverse effects of mutual coupling, an efficient compensation mechanism is integrated into the Capon direction-finding algorithm. This mechanism relies on realistic electromagnetic modeling in which mutual coupling is represented using Toeplitz-structured coupling matrices. Through computer simulations, the influence of various system parameters on the algorithms performance is evaluated, with particular emphasis on its resolution capability and estimation accuracy. The results clearly demonstrate that incorporating mutual coupling compensation significantly enhances the accuracy of the 2D Capon algorithm.

Dipole Antenna Arrays With Inherently High Port Isolation Levels

Objective.Temporal interference stimulation (TIS) has recently been introduced for non-invasive deep brain stimulation (NDBS). While numerous studies have highlighted its advantages over conventional technologies, TIS still encounters challenges such as limited resolution and a lack of validation using human-like models. This article introduces an innovative method for NDBS which alleviates the resolution limit.Approach.We utilize as our excitation a 1.5 GHz microwave carrier modulated by a 10 Hz envelope. The microwave carrier enables strong electromagnetic focusing while the envelope triggers neural activity. To form this excitation, two dipole antenna arrays are placed around the head for the generation ofy- andz-directed electric fields (E-field). Current excitations to the antenna arrays are tuned to control (i) theE-field to the desired focality position and (ii) its direction at the focality position. Full-wave simulations with a realistic head model are conducted to demonstrate the method.Main results.In the deep brain region, the cross-sectional focality sizes (75% threshold) are 0.73 cm2, 1.18 cm2and 2.45 cm2in theXOY, YOZandXOZplanes, respectively. The focality is much smaller than previously reported in the conventional method with kHz carrier waves. Further, theE-field direction at the focality can be steered along theyz-plane by adjusting the excitation weights of the antenna arrays. Multiphysics simulations on temperature distribution and specific absorption rate (SAR) show that the maximum temperature increase within a 30-minute stimulation session is 0.76 °C and the maximum SAR1gis 2.70 W kg-1. Both measures are within commonly accepted safe operation ranges.Significance.Compared to conventional TIS methods that utilize kHz carrier signals, our proposed approach achieves drastically improved spatial resolution and enables precise steering of theE-field. The proposed work holds significant potential for clinical applications, offering enhanced resolution and reduced input power for NDBS.

An accurate prediction method for the analysis of scattering property of tightly coupled antenna arrays associated with feeding circuits is proposed based on the generalized scattering matrix theory. The feeding circuit parameters and antenna far-field characteristics are integrated by analyzing the power transferring relationship as a microwave network, and the prediction is systematically addressed through the renormalization process. To demonstrate the proposed method, a 10 × 10 UWB tightly-coupled dipole array (TCDA) operating at 2∼18 GHz is designed. Numerical experiments show that the relative error for monostatic radar cross-section (RCS) prediction compared with full-wave simulation tools achieves less than 0.2% in both far-field amplitude and phase. Compared with the state-of-the-art methods, the prediction accuracy is improved. Furthermore, the differential evolution algorithm is applied to optimize the feeding circuit to achieve a low RCS state, which further highlights the practicality of this method.

In recent years, per/polyfluoroalkyl substances (PFAS) have gained widespread attention owing to their potential hazards to human health and the environment. However, their chemical characteristics render detection and adsorption challenging. In this study, we controlled the density of polyfluoroalkylsilane (PFS) on silicon wafers from sub-monolayers to monolayers. Two PFSs, namely, (CF3(CF2)5(CH2)2SiCl3 and CF3(CF2)9(CH2)2SiCl3), were used to investigate the effect of the -CF2- length on the adsorption characteristics. For each surface, we measured the change in surface energy due to the adsorption of perfluorooctanoic acid (PFOA) in an aqueous solution via contact angle measurements. Then, the maximum surface excess (Γmax), Langmuir coefficient (KL), and initial surface energy (σ0) were determined based on a Szyszkowski-Langmuir model. We found that Γmax and KL have maxima in the sub-monolayer region and were smaller in monolayers or over monolayer regions. Interchain interactions in polyfluoroalkylsilane monolayers and their interaction mechanisms with PFOA were logically deduced. These findings strongly suggest that the side of the PFS chain rather than the top is a strong adsorption site for PFAS. Recent studies have revealed that the stratified dipole array (SDA) model can explain intermolecular PFAS interactions, and the results of this study are consistent with these findings. This study provides a new direction for the development of functional surfaces for the efficient detection and adsorption of PFAS.

This paper introduces an innovative design and analysis of a magneto-electric dipole antenna exhibiting high-gain, ultra-wideband operation, and stable radiation characteristics in the 60-GHz mm-wave band. Furthermore, the trapped printed gap waveguide (TPGW) technology is presented as a low-cost, minimal-loss, and low-dispersion guiding structure to feed the proposed antenna. The antenna covers a relative matching bandwidth of over 33.33% from 50 to 70 GHz with a maximum gain up to 8 dBi. In addition, the antenna is integrated with a perforated dielectric substrate layer lens on the antenna’s broadside location, enhancing the gain by an average of 3 dB along its entire operational bandwidth. Moreover, an efficient approach for designing a large ME dipole antenna array and its corporate feeding network is presented. Both ME-dipole sub-arrays and the out-of-phase power divider with WR-15 standard interface are designed and studied separately, where a systematic design procedure is presented to obtain initial design parameters. A 2 × 2 planar antenna array is designed and implemented, featuring proper integration between the radiating elements and a differentially fed wide-bandwidth TPGW power divider. Then, the operation of the individual components has been assessed using simulation and measurements. Furthermore, an in-depth mathematical analysis is presented to investigate the potential resonance conditions arising from disparities in complementary components. Consequently, a proposed solution is provided to break the resonance loop and shield the two opposing sub-arrays. The 2 × 2 array of ME-dipoles has overall dimensions of 1.61.4 and demonstrates an impedance bandwidth (– 10 dB) exceeding 33.33 at 60 GHz, with a peak gain of over 18 dBi.

ABSTRACTThis paper presents comprehensive circuit models for the design and analysis of ultrawideband shared aperture antenna arrays. A novel semi‐analytical approach is developed by modifying the previous equivalent circuit model to enable the calculation of the electromagnetic (EM) transparency of dipole array unit cells. Based on the EM transmission characteristics of the low‐band dipole, an accurate circuit‐based method is introduced for calculating the input impedance of a shared aperture antenna. Notably, the only full‐wave simulation required is that of the standalone high‐band antenna. To demonstrate the effectiveness of the proposed technique, two distinct shared aperture dipole array designs are presented. In both cases, the high‐band antennas are implemented using tightly coupled dipole array (TCDA) elements. The first design achieves a 26.2:1 impedance bandwidth with active VSWR < 2.3 and a low‐profile height of , where denotes the free‐space wavelength at the lowest operating frequency. The second design achieves a 33.3:1 bandwidth with active VSWR < 3 and a profile height of just . The average total efficiencies of the two designs are 0.86 and 0.85, respectively.

Partial discharge (PD) is a localized dielectric breakdown in high- voltage insulation systems that can lead to catastrophic equipment failure if undetected. Early and accurate detection of PD is critical in ensuring the reliability and longevity of high-voltage equipment such as transformers, GIS (Gas Insulated Switchgear), and cables. Traditional sensors and narrowband antenna systems have limited sensitivity and frequency range, making them less effective for detecting weak PD signals over wide spectra. The narrow operational bandwidth and low sensitivity of conventional PD detection systems impede accurate localization and characterization of PD phenomena, especially under noisy or variable frequency conditions. There is a pressing need for a robust detection mechanism that combines broad frequency response with high detection sensitivity. This study proposes a Broadband Antenna System specifically designed for PD signal acquisition. The system incorporates a log-periodic dipole array (LPDA) antenna integrated with a low-noise amplifier (LNA), coupled to a high-speed digitizer. The LPDA provides ultra-wideband coverage from 50 MHz to 1.5 GHz, enabling the capture of various PD signatures. Finite Element Method (FEM)-based simulations in CST Microwave Studio validate the antenna design. Real-time testing is performed in a controlled high-voltage laboratory environment using a 100 kV test transformer and calibrated PD sources. The proposed antenna system demonstrated a 25% improvement in sensitivity and a 40% increase in detection range compared to standard narrowband antennas. It accurately detected PD pulses with charge magnitudes as low as 5 pC under noisy environments.

A cylindrical tightly coupled dipole array (TCDA) with circular polarization

A Low-Profile Circularly Polarized Magnetoelectric Dipole Array Based on Micrometal Additive Manufacturing for Sub-THz Applications

Electrical resistivity tomography (ERT) is a popular geophysical tool used for a variety of prospecting. To derive a true resistivity model from the observed apparent (ERT) data, the smoothness-constrained least squares inversion method is still frequently employed. However, the smooth inversion usually obtained unclear interfaces of resistivity changes, which exacerbates the final interpretation of the inverted model. To overcome the drawback related to the smoothness-constrained inversion, I proposed using the Euler deconvolution (ED) method as a layer interface detector for interpreting ERT data. By employing the ED approach, the boundaries of various resistivity zones could be automatically identified rather than relying on manual detection. To achieve this, the efficiency of the ED method in interpreting ERT data was evaluated using both synthetic models and actual field cases. In this paper, five models were used to simulate different scenarios of horizontally stratified and undulating layers using RES2DMOD software. The response of these models was calculated using the Wenner and dipole–dipole array. Then the synthetically apparent data were inverted using Res2dinv software. The results obtained from the inversion process were interpreted using the ED method. The overall findings demonstrate that, for both the simulated and actual data, the calculated Euler depth solution closely matches the layer interface of the inverted resistivity sections. A structure index of 0 produced the tightest cluster solutions. This study highlights that in order to improve the interpretation of the inversion results, the ED approach can be utilized as an additional processing tool for ERT data interpretation.

Recently, unique surface properties of poly- and perfluoroalkyl substances (PFAS) have been revealed to be derived from a two-dimensional (2D) packing of perfluoroalkyl (Rf) groups with perpendicularly standing orientation, i.e., the end-on orientation, which is revealed by the stratified dipole arrays (SDA) model. This indicates that analysis of the 2D aggregation of Rf groups is crucial for understanding the PFAS-specific properties, and analysis of the primary structure alone is insufficient. In the present study, we employ an analytical method of backscattering Raman spectrometry to explore the 2D aggregation of Rf groups in terms of molecular orientation. Measurements of solid particles of perfluoro-n-alkane with theoretical consideration of the Raman activity on backscattering optical arrangement make us find useful marker bands derived from the Rf groups. Analysis of the band enables us to determine the end-on orientation of the Rf chain about the surface of bulk PFAS: when the Rf chains are end-on oriented, the bands assigned to a specific symmetry species selectively disappear, whereas the other Raman-active bands remain. In short, the disappearance of the marker bands makes us determine the end-on orientation very easily. In addition, we demonstrate that the marker band can be used to visualize in-plane distribution of the end-on orientation by utilizing mapping measurements.

ABSTRACTThis letter presents a quasi‐conformal transformation optics (QCTO) based two‐dimensional (2D) flat Luneburg Meta‐Lens (LML) antenna with zero focal length for millimeter‐wave beam switching applications. In this study, we employed metamaterial unit cells of periodicity 0.14 λ0 (where λ0 is the free‐space wavelength at 28 GHz) to realize the refractive index distribution on the LML aperture having a diameter of 48 mm. The proposed LML is fed by five planar dipole antenna arrays, enabling wide‐angle beam switching. The fabricated prototype of the proposed LML antenna is experimentally validated in a free‐space environment, achieving a maximum measured gain of 14.2 dBi with a gain enhancement of 9.49 dB. The key merits of the proposed LML antenna encompass compactness of profile, ease of fabrication and wide‐angle beam switching up to ± 51° with very low scan loss of less than 1.7 dB. These characteristics make it highly suitable for millimeter‐wave applications, including 5 G base stations, automated vehicles, radar systems and far‐field imaging.

3D-Printed All-Metal Modular Low-Profile Ultrawideband Tightly Coupled Dipole Arrays

HighlightsWhat are the main findings?New structure dipole antenna.Minimalist feeding method.What is the implication of the main finding?Dipoles close to each other in an arc shape between elements, making the mutual coupling and bandwidth increase greatly.The specially designed feed network makes the feed mode greatly simplified and the profile height extremely low.This article presents a novel tightly coupled dipole array (TCDA) with a bandwidth of 26.2:1 (VSWR < 3) across 0.20–5.23 GHz. By adding a new dual-stopband resistive frequency selective surface (RFSS) between the dipole and the floor, the short-circuit points formed by the floor at the frequency points corresponding to λ = 2 h and h are both eliminated (h is the height from the antenna to the floor). A specially integrated feed network is also applied to significantly reduce the complexity and profile height to 0.05 λlow. The simulation and experimental results show that the designed TCDA has extremely wide bandwidth, good directivity and beam scanning potential. Compared with previous designs, it greatly extends the bandwidth, improves the gain, reduces the profile height, and simplifies the feeding method.

Design and optimization of low-loss, high-gain metamaterial-based log-periodic dipole array antenna for full Ka-band coverage