Dipole Antenna Research Articles

Antenna RCS minimization using load tuning

Abstract This paper synthesizes antenna RCS using load tuning, beginning with the derivation of the theoretical load impedance to achieve minimum RCS (MRCS) based on antenna radiation and conjugate-matched scattering parameters. This condition is utilized to obtain feasible MRCS zones and minimize backward RCS (BRCS) for the dipole and microstrip patch antennas. The dipole antenna exhibits a full feasible MRCS zone with a BRCS reduction of 77 dB at the resonant frequency, a 63% relative −10dB reduction bandwidth, and a full plane of reduction angles compared to the conjugate-matched condition. However, mismatching of MRCS loading significantly affects the dipole received power. Conversely, the microstrip patch antenna has a feasible MRCS zone that excludes forward directions and demonstrates a negligible mismatching level with a BRCS reduction of 35.5 dB at the resonant frequency, a 0.67% relative reduction bandwidth, a 50° reduction in H-plane, and a 20° reduction in E-plane compared to the conjugate-matched condition. Tuning the load reactance between conjugate-matched and MRCS loadings results in a trade-off between BRCS reduction and the received power. The calculated MRCS load for specific incident direction is applicable for nearby incidence directions, demonstrating applicability with misalignment. The findings validate the efficiency of using load-tuning method with the derived condition to minimize RCS within specific incident angles.

Modeling and Simulation of Electric and Magnetic Fields of a Short Dipole Antenna at Low Frequencies in the Far Field

Modeling and Simulation of Electric and Magnetic Fields of a Short Dipole Antenna at Low Frequencies in the Far Field

A Dual‐Polarized Wide‐Angle Scanning Linear Phased Array Antenna With Simple Decoupling Structure

ABSTRACTA dual‐polarization linear phased array with a simple decoupling structure is designed for wide scanning in this letter. The suggested antenna is made up of two printed dipole antennas that are orthogonally arranged and have a high cross‐polarized isolation. Metal sheets cladding on antenna substrates serve as a decoupling structure, with an array element spacing of 0.48 . A linear phased array of seven elements is fabricated and measured to ensure that the planned array is feasible. The simulated and measured results demonstrate that the phased array can scan its main beam up to ±75° in dual‐polarized excitations at 5.6–6.4 GHz. The co‐polarized mutual coupling is below −28 dB, and the active reflection coefficient of the element is less than −15 dB.

Infrared thermochromic antenna composite for self-adaptive thermoregulation

Self-adaptive thermoregulation, the mechanism living organisms use to balance their temperature, holds great promise for decarbonizing cooling and heating processes. This functionality can be effectively emulated by engineering the thermal emissivity of materials to adapt to background temperature variations. Yet, solutions that marry large emissivity switching (Δϵ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\varDelta \\epsilon$$\\end{document}) with scalability, cost-effectiveness, and design freedom are still lacking. Here, we fill this gap by introducing infrared dipole antennas made of tunable thermochromic materials. We demonstrate that non-spherical antennas (rods, stars and flakes) made of vanadium-dioxide can exhibit a massive (~200-fold) increase in their absorption cross-section as temperature rises. Embedding these antennas in polymer films, or simply spraying them directly, creates free-form thermoregulation composites, featuring an outstanding Δϵ~0.6\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\varDelta \\epsilon \\sim 0.6$$\\end{document} in spectral ranges that can be tuned at will. Our research paves the way for versatile self-adaptive heat management solutions (coatings, fibers, membranes, and films) that could find application in radiative-cooling, heat-sensing, thermal-camouflage, and other.

An experiment to measure electromagnetic memory

Abstract We describe an experiment to measure the electromagnetic analog of gravitational wave memory, the so-called electromagnetic (EM) memory. Whereas gravitational wave memory is a residual displacement of test masses, EM memory is a residual velocity (i.e. kick) of test charges. The source of gravitational wave memory is energy that is not confined to any bounded spatial region: in the case of binary black hole mergers the emitted energy of gravitational radiation as well as the recoil energy of the final black hole. Similarly, EM memory requires a source whose charges are not confined to any bounded spatial region. While particle beams can provide unbounded charges, their currents are too small to be practical for such an experiment. Instead we propose a short microwave pulse applied to the center of a long dipole antenna. In this way the measurement of the kick can be done quickly enough that the finite size of the antenna does not come into play and it acts for our purposes the same as if it were an infinite antenna.

A dual-band dipole array antenna with fan-beam radiation for biomedical and telecommunications applications

This study introduces a new technique for achieving dual-band functionality in a printed dipole antenna with integrated balun feeding without additional elements. By employing an optimization algorithm, the fundamental parameters of the antenna are extracted, resulting in an antenna design that operates effectively in two distinct frequency bands of 2.4–2.5 and 5–6 GHz for WLAN/ISM and biomedical applications. By implementing the proposed design in a two-element array structure, the antenna successfully achieved a fan-beam radiation pattern in both frequencies. The array antenna exhibits fan-beam radiation patterns and peak gains of 6.90 dB and 7.84 dB, respectively, in two frequency bands: 2.06–2.52 GHz and 5.09–5.93 GHz. According to the proposed design, the array antenna has measured half-power beamwidths (HPBWs) of 38.34° and 25.14° in the two frequencies specified. The overall dimensions of the antenna are 1.100λ × 0.563λ × 0.004λ. This research design offers advantages such as smaller dimensions, higher gain, and a more straightforward structure compared to dual-band array antennas with fan beam radiation patterns.

Decoupled Dipole Arrays Empowered by Invisible Complex Poles in Epsilon‐Near‐Zero Metamaterials

AbstractEvanescent waves, characterized by an exponential decay in propagation, have witnessed significant advancements in far‐field imaging and near‐field sensing applications. However, incoming evanescent waves can excite guided resonance inside a dielectric slab, resulting in a rapid growth of transmission coefficient toward infinity at the pole points. Such evanescent‐wave excited resonance benefits super‐resolution applications yet causes severe crosstalk in highly integrated multi‐channel devices. Here, the invisible complex poles are discovered in the transmission spectra of epsilon‐near‐zero (ENZ) metamaterials and demonstrate the striking suppression of near‐field crosstalk enabled by the anomalous transmission beyond the critical angle. Equipped with an ENZ metamaterial spacer, collinear dipole arrays exhibit 9.2 dB improvement in near‐field isolation among interior dipoles at a distance of less than one wavelength. Experimental measurements show negligible influence on the intrinsic impedance matching and radiation patterns of the dipole antennas. The discovered field divergence effect from the disappearance of real‐valued pole singularity in ENZ metamaterials offers an alternative solution for highly compact arrays in full duplex communication and multiple‐input multiple‐output technology.

Design and Construction of a 500–800 MHz Square Spiral Dipole Microstrip Antenna Structure

An antenna can be used to detect an object. The dimensions of the antenna also affect the working frequency, the smaller dimensions, the higher the working frequency and the closer the antenna range to radiate waves. Therefore, a microstrip antenna with a small dimension size is needed, but the antenna radiation distance capability for radar systems still needs to be reduced. A microstrip dipole antenna with a spiral shape, measuring 5 cm, was meticulously designed and fabricated. The square dipole antenna, featuring an optimal design with the arm structure rotated in a clockwise direction, achieved an impressive return loss of -27.54dB with a VSWR of 1.83. The engineering refinement of the antenna design involved the addition of a square shape, which led to a significant and impressive improvement in performance. The second spiral antenna, operating at a frequency of 805MHz with an impressive bandwidth of 57MHz, exhibited a remarkable return loss of -30.83dB and a VSWR of 1.07.

High sensitivity measurement of ULF, VLF, and LF fields with a Rydberg-atom sensor.

Fields with frequencies below megahertz are challenging for Rydberg-atom-based measurements, due to the low-frequency electric field screening effect caused by the alkali-metal atoms adsorbed on the inner surface of the container. In this paper, we investigate electric field measurements in the ultralow frequency (ULF), very low frequency (VLF), and low frequency (LF) bands in a Cs vapor cell with built-in parallel electrodes. With optimization of the applied DC field, we achieve high-sensitive detection of the electric field at frequencies of 1 kHz, 10 kHz, and 100 kHz based on the Rydberg-atom sensor, with the minimum electric field strength down to 18.0 μV/cm, 6.9 μV/cm, and 3.0 μV/cm, respectively. The corresponding sensitivity is 5.7 μV/cm/Hz1/2, 2.2 μV/cm/Hz1/2, and 0.95 μV/cm/Hz1/2 for the ULF, VLF, and LF fields, which is better than a 1-cm dipole antenna. Besides, the linear dynamic range of the Rydberg-atom sensor is over 50 dB. This work presents the potential to enable more applications that utilize atomic sensing technology in the ULF, VLF, and LF fields.

A Low-Profile Magnetoelectric Dipole Antenna Based on Comb Structure and Its Application in Frequency-Scanning Array With Ground

A Low-Profile Magnetoelectric Dipole Antenna Based on Comb Structure and Its Application in Frequency-Scanning Array With Ground

A Compact Circularly Polarized Filtering Dipole Antenna With Co-Layered Printed Ring Structures

A Compact Circularly Polarized Filtering Dipole Antenna With Co-Layered Printed Ring Structures

Pattern-Reconfigurable Dipole Antenna Based on Odd- and Even-Mode Principle for 5G-NR Communications

Pattern-Reconfigurable Dipole Antenna Based on Odd- and Even-Mode Principle for 5G-NR Communications

Radiation Pattern Analysis and Phase Shifter for Base Station Mobile Communication Circular Array Antenna at 900MHz Frequency by Using 4NEC2X Software

Background: This paper presents the utilization of phase shifters to manipulate and control the radiation patterns in Uniform Circular Array (UCA) antennas. UCAs, known for their 360-degree coverage and symmetrical radiation patterns, are enhanced by incorporating phase shifters, enabling dynamic beam steering and pattern shaping. Materials and Methods: A uniform circular antenna array operating at 900 GHz frequency has been intended for use in base stations using 4NEC2X simulation software. Results: A single-element dipole antenna having a 2.14 dBi gain is used as a base for constructing a uniform 0.5 λ spacing circular array. The number of elements gradually increased from 2 to 12, raising the gain to 12.3 dBi. HPBW decreased both in vertical and horizontal plans from 80o to 60o and 360o to 20o respectively this implies that the circular array antenna's directivity is enhanced. The eight-element array beam scanning was performed from 0o to 360o without any distortion in radiation pattern, gain, and directivity, contradictory with the linear array. Conclusions: The studied case and simulation output illustrate the impact of the element numbers and phase shifter configurations on properties of the radiation pattern of the uniform circular array can be obtained when increasing the number of elements, the gain increases too and scanning the main beam without any change and distortion

Wideband and Low-Profile Array of Tightly Coupled Dipole Subarrays

This letter introduces a novel wideband, low profile, tightly coupled dipole subarray for wireless communication systems. The proposed subarray, composed of 3 × 3 unit elements, offers a planar structure with high aperture efficiency. The unit element is a bow-tie-shaped tightly coupled dipole antenna covered by a frequency-selective surface for wideband operation. Using power dividers with quarter-wave transformers, the proposed subarray achieved an impressive impedance-matching bandwidth of 28.6–41.6 GHz (37.8%). This wideband performance was maintained in a 4 × 4 array configuration as well. The antenna’s low-profile design (0.08λc) and high aperture efficiency (77.2%) set it apart from existing wideband patch array antennas, making it a promising candidate for future wireless communication applications.

Physical analysis of high refractive index metamaterial-based radiation aggregation engineering of planar dipole antenna for gain enhancement of mm-wave applications

A metamaterial-incorporated high-gain and broadband dipole antenna is proposed for 5G mm-wave applications. The designed high refractive index metamaterial (HRIM) properties are presented in detail with supporting results. The proposed dipole antenna achieved broadband features, and the antenna gain increased significantly by incorporating HRIM in the electromagnetic (EM) wave propagation path. Besides, the EM wave aggregation engineering of utilizing the HRIM on the dipole antenna is analyzed using the electric field, magnetic field, and power flow distributions. Both conventional and HRIM-based dipole antenna (HRIMDA) were fabricated on thin (0.254 mm) Rogers RT5880 substrate material with a low dielectric constant of 2.2, where the noticeable gain enhancement by HRIM is observed. The measured results show the operational bandwidth (BW) from 23 to 38 GHz frequency, and the highest gain of 9.5 dBi is accomplished at 35 GHz frequency. Finally, a four-element MIMO configuration is numerically and experimentally analyzed where the isolation of the two conjugated MIMO elements is < − 20 dB. The MIMO parameters like envelop correlation coefficient (ECC) < 1 × 10–3 and diversity gain (DG) value of > 9.9 were also achieved. Hence, the proposed HRIM base dipole antenna is a potential candidate for 5G mm-wave applications.

Excitation and manipulation of toroidal dipole response in an antenna

The toroidal dipole is always overlooked due to its relatively weak interaction with the electromagnetic fields, but it actually exhibits tremendous potential for the design of advanced photonic devices. Here, we demonstrate the existence of toroidal dipole in plasma antenna system, which is rarely observed in the antenna design. It consists of a half-wavelength antenna and eight plasma rings to excite the toroidal dipole to enhance the electromagnetic radiation of the whole antenna system, whose mechanism is different from conventional antenna, which is a multiband antenna. We further confirm that the hybrid mode, which combines the toroidal dipole and multipole moments, can be dynamically adjusted to control both return loss and the opening of operating windows. This allows for flexible tuning of the multiband antenna simply by manipulating the response of the toroidal dipole. Furthermore, the toroidal dipole antenna is stable in dusty plasma, making it suitable for solving the problem of ‘blackout’ phenomena in aerospace communications, which exhibits the additional benefits of reduced cost and easier to manufacture.

Investigation and analysis of design techniques for ultra-wideband CMOS on-chip dipole antennas for 6G sub-THz applications

This article explores different techniques to improve the impedance bandwidth of on-chip dipole antennas in the sub-THz frequency range. Increasing the area of the dipole antenna has shown considerable improvement in bandwidth. However, this violates the design rule checks (DRC) of the foundry. Various topologies, such as squared-slotted dipole, meandered-slotted dipole, and straight-slotted dipole antennas, are introduced and implemented to increase the width of the on-chip antennas and thus the impedance bandwidth while meeting the DRC rules. All three topologies show better performance in terms of providing improved bandwidth. The straight-slotted technique is adopted as it offers less complexity and flexibility. The behavior of the impedances for different widths implemented by the straight-slotted topology has been analyzed in detail. A 6-strip straight-slotted dipole antenna results in an ultra-wide impedance bandwidth ranging from 76–262 GHz with a fractional bandwidth of 110% and a gain of −0.6 dBi at 159 GHz, while occupying a small silicon area of 567μm×112μm. To the best of the authors’ knowledge, this is the highest fractional bandwidth that is reported to date at these frequencies.

A Computer Model of a Marx Generator Charging a Coaxial Switched Wave Oscillator

The paper describes an axisymmetric Finite-Difference Time-Domain computer model of a coaxial Switched Wave Oscillator integrated with a dipole antenna. The model analyzes the operation of a realistic circuit model of a multistage Marx generator that charges the oscillator to a high voltage. The initial field distribution is calculated with an electrostatic finite-difference method solver to speed up the time-domain analysis. The work presents the results of our circuit model of a Marx generator’s simulations of the charging phase, followed by the results from the discharge phase, using our axisymmetric Finite-Difference Time-Domain model. Our work describes new and fast numerical solvers that can observe the operation of Switched Wave Oscillator systems (also considering the connected antenna). The codes could be used in the process of designing such a system. Advanced boundary conditions modeling the spark gap and oscillator’s excitation set our work apart from the other attempts in the literature.

A low-profile ultra-wideband magneto-electric dipole antenna for ground penetrating radar

ABSTRACT Ultra-wideband antennas that operate at low frequencies usually have a large geometry, which makes them very limited in practical engineering application environment where space is often constrained. In this paper, a novel low-frequency low-profile ultra-wideband magneto-electric (ME) dipole antenna is designed for the application in ground penetrating radar (GPR) to detect deeply buried targets. The antenna is designed at the operation frequency of 230 MHz, so that the objects that are buried as deep as 1.5 m can be detected. Compared to the traditional low-frequency _antennas, it has a profile as low as 740 mm × 140 mm × 150 mm ( 0.49 λ × 0.09 λ × 0.10 λ ). Based on the simulation analysis and validation measurements, the proposed ME dipole antenna has a wide impedance bandwidth for S 11 < − 10 dB from 135 MHz to 382 MHz even when environmental influence is considered. The antenna is further validated with a GPR experiment, where a pipeline with a diameter of about 200 mm at 1200 mm beneath the road surface is successfully detected by an impulse GPR system where the proposed antennas are integrated.

Simulation Design of a Triple Antenna Combination for PET‐MRI Imaging Compatible With 3, 7, and 11.74 T MRI Scanner

ABSTRACTThe use of electromagnetism and the design of antennas in the field of medical imaging have played important roles in clinical practice. Specifically, magnetic resonance imaging (MRI) utilizes transmission and reception antennas, or coils, that are tuned to specific frequencies depending on the strength of the main magnet. Clinical scanners operating at 3 Teslas (T) function at a frequency of 127 MHz, while research scanners at 7 T operate at 300 MHz. An 11.74 T scanner for human imaging, which is currently under development, will operate at a frequency of 500 MHz. MRI allows for the high‐definition scanning of biological tissues, making it a valuable tool for enhancing images acquired with positron emission tomography (PET). PET is an imaging modality used to evaluate the metabolism of organs or cancers. With recent advancements in the development of portable PET systems that can be integrated into any MRI scanner, we propose the design based on electromagnetic simulations of a triple‐tuned array of dipole antennas to operate at 127, 300, and 500 MHz. This array can be attached to the PET inset and used in 3, 7, or 11.74 T scanners.