Dipole Array Research Articles

Observation of electric polarization continuity in graphite

Electric polarization (dielectric) continuity refers to the continuity of the dipole-dipole interaction in an electric dipole array. This work introduces the concept of polarization continuity and discovers that the polarization continuity decreases upon bending, as shown by the decrease of the electret voltage upon bending, with graphite as the material. The voltage is decreased by ≤ 41% by bending the material, due to the reduction in the dipole-dipole interaction and the decrease in the degree of carrier-atom interaction at the bend. This work also discovers that the voltage scales by series connection, with the voltage doubled when two essentially identical unbent specimens are connected in series without connection bending, but the series voltage is approximately halved when the connection is bent. This is shown by comparing a silver-paint butt-joint unbent series connection and a silver-paint-attached aluminum-foil bent series connection. The former gives voltage essentially equal to the sum of the voltages of the two disconnected unbent specimens, but the latter gives voltage below the sum by 52%. The electric field does not change upon series connection, as expected. The voltage causes current to pass through a series load resistance according to Ohm's Law. The voltage changes sign upon polarity reversal, with the magnitude slightly smaller after the reversal.

Improved Beam Steering Method Using OAM Waves

Orbital Angular Momentum (OAM) is an intrinsic feature of electromagnetic waves which has recently found many applications in several areas in radio and optics. In this paper, we use OAM wave characteristics to present a simple method for beam steering over both elevation and azimuth planes. The design overcomes some limitations of traditional steering methods, such as limited dynamic range of steering, the design complexity, bulky size of the steering structure, the limited bandwidth of operation, and low gain. Based on OAM wave characteristics, the proposed steering method avoids design complexities by adopting a simple method for generating the OAM-carrying waves. The waves are generated by an array of Planar Circular Dipole (PCD) elements. These elements are designed to cover a wide bandwidth range between 3 and 30 GHz. The transmitting array shows an enhanced gain value from 8.5 dBi to almost 11.5 dBi at the broadside angle. Besides the enhanced PCD-based OAM generation, the novelty of the design lies in a new method of beam steering. Beam steering is then performed by controlling the electrical feeding of the PCD elements; the beam azimuthal location is managed by turning off some of the PCD elements, while the elevation is determined by changing the gradient phase of excitation for the turned-on PCD elements. Detailed analysis of the steering method is carried out by finding the mathematical model of the system and the generated waves. The performance has been verified through numerical simulators.

A Dual-Band Dipole Array Antenna With Fan-Beam Characteristics for C- and X-Band Applications

A Dual-Band Dipole Array Antenna With Fan-Beam Characteristics for C- and X-Band Applications

Lattice relaxation effects on the collective resonance spectra of a finite dipole array.

Dielectric/plasmonic lattice relaxation spectroscopy is theoretically discussed in this work. A lattice relaxation effect generally occurs in nanocrystals, which means that from the bulk phase to the crystal surface, lattice parameters show a gradual shift. Here, lattice relaxation is introduced into finite polarizable point arrays or rod arrays as an adjusting tool, and its effect on lattice resonance extinction spectrum peaks is calculated. DDA (discrete dipole approximation) and FDTD (finite difference time domain) methods are applied. Different from an ideal infinite array, a finite array exhibits a broad, rippled extinction spectral peak. The application of an expanded/contracted lattice relaxation to the finite array can compress the ripple on one shoulder of the peak, as a cost, and the other shoulder of the peak gets more rippled, showing a "ripple transfer" effect. The strategy introduced in this work can contribute to the micro/nano optical measurement, on-chip adjustable optical cavity for OPOs (optical parameter oscillators)/lasers and controlling of fluorescence or hot-electron chemistry.

Compact Magneto-Electric Dipole Array With Wide Beam Scanning Range for 5G NR Bands

Compact Magneto-Electric Dipole Array With Wide Beam Scanning Range for 5G NR Bands

A Low-Profile Ultra-Wideband and Wide-Scanning Phased Array for UHF Applications

This article presents a novel low-profile ultra-wideband and wide-scanning array antenna using the transversely connected folded tightly coupled dipoles array (TCF-TCDA). The tightly coupled folded dipole arms are used to extend the operational frequency band with a simple feed structure. The capacitively-loaded metallic walls are adopted to move the problematic common-mode resonance out of the desired band and mitigate the bandwidth-limiting loop mode at the lower frequency, as well as reducing the weight and cost. A meta-surface-based wide angle impedance matching (MS-WAIM) layer is used to improve the beam scanning ability and lower the antenna profile, which consists of the star-shaped patches loaded on the dipole element. To demonstrate the wideband and wide scanning-range capability, a prototype is designed with an 8:1 bandwidth (0.41–3.3 GHz) at broadside, a scanning range of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pm \mathrm{75}^{\circ }$ </tex-math></inline-formula> from 0.5 to 3.25 GHz (6.5:1 bandwidth) in the E- and D-planes and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pm \mathrm{50}^{\circ }$ </tex-math></inline-formula> from 0.6 to 3.3 GHz (5.5:1 bandwidth) in the H-plane for active VSWR < 3.6. The proposed antenna has a very low profile, which is only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.07\lambda _{\mathrm {low}}$ </tex-math></inline-formula> at the lowest operating frequency. A 16 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 16 array prototype is fabricated and measured. Experimental results show that the design and measurement results have good agreement. The proposed antenna has an ultra-wide bandwidth, a wide scanning range, a very compact size and a low cost, which is a good candidate for modern wireless system.

Ultra-Wideband Tightly Coupled Dipole Array Fed by a Tapering Meandered Balun

Ultra-Wideband Tightly Coupled Dipole Array Fed by a Tapering Meandered Balun

Fast rotating dipole array inducing large dielectric response in a Ruddlesden–Popper hybrid perovskite ferroelastic

A 2D RP hybrid perovskite shows dynamic rotating motion of the polar rotor which inducing ferroelasticity and a tremendous dielectric response. This study provides a new vision for the development of dynamic functional materials.

Electrical resistivity tomography and ground‐penetrating radar methods to detect archaeological walls of Babylonian houses near Ishtar temple, ancient Babylon city, Iraq

AbstractA survey was conducted to investigate buried archaeological walls near the Ishtar temple in the ancient Babylon city using electrical resistivity tomography and ground‐penetrating radar methods. The survey includes applying 12 electrical resistivity tomography profiles using dipole–dipole array and a ground‐penetrating radar grid of 55 m × 50 m using 250 MHz antenna. Although the buried walls are consisting of mudbrick masonry and are embedded in a clayey environment, the electrical resistivity tomography method is still able to differentiate the tiny differences between the host materials and the buried walls, which show distinctive wall‐like features with resistivity values ranging between 9 and 15 Ω m. These features may reflect underground‐buried walls with a general width reaching about 2.5 m. The comparison of ground‐penetrating radar profiles and their corresponding electrical resistivity tomography profiles presents that the main architectures are coinciding well. The analysis of the geometry and composition of the walls around the Ishtar temple suggested that the wall‐like reflections on the ground‐penetrating radar slice at a depth between 140 and 150 cm (may be shallower) are underground‐buried walls. These wall‐like reflections show a special trend and orientation that indicate that they may be the remains of rooms belonging to two small houses or the remains of one big private house.

Tier-based formalism for safety assessment of custom-built radio-frequency transmit coils.

The purpose of this work is to propose a tier-based formalism for safety assessment of custom-built radio-frequency (RF) coils that balances validation effort with the effort put in determinating the safety factor. The formalism has three tier levels. Higher tiers require increased effort when validating electromagnetic simulation results but allow for less conservative safety factors. In addition, we propose a new method to calculate modeling uncertainty between simulations and measurements and a new method to propagate uncertainties in the simulation into a safety factor that minimizes the risk of underestimating the peak specific absorption rate (SAR). The new safety assessment procedure was completed for all tier levels for an eight-channel dipole array for prostate imaging at 7 T and an eight-channel dipole array for head imaging at 10.5 T, using data from two different research sites. For the 7 T body array, the validation procedure resulted in a modeling uncertainty of 77% between measured and simulated local SAR distributions. For a situation where RF shimming is performed on the prostate, average power limits of 2.4 and 4.5 W/channel were found for tiers 2 and 3, respectively. When the worst-case peak SAR among all phase settings was calculated, power limits of 1.4 and 2.7 W/channel were found for tiers 2 and 3, respectively. For the 10.5 T head array, a modeling uncertainty of 21% was found based on B1 + mapping. For the tier 2 validation, a power limit of 2.6 W/channel was calculated. The demonstrated tier system provides a strategy for evaluating modeling inaccuracy, allowing for the rapid translation of novel coil designs with conservative safety factors and the implementation of less conservative safety factors for frequently used coil arrays at the expense of increased validation effort.

Independent control method for plasmonic skin depth based on transformation from spoof surface plasmon polaritons to bound states in the continuum

A metal plate array (MPA) is the complementary structure of a metal hole array and forms spoof surface plasmon polaritons (SSPPs) supported by parallel plate modes in a unit cell. A ring dipole array, which is a periodic structure designed by providing an aperture in the conductive part of the unit cell of an MPA, has the potential to produce bound states in the continuum (BICs). In this paper, the transformation from SSPPs to BICs is confirmed using these two structures by broadening the aperture in the unit cell. Making use of this phenomenon, control of the skin depth of surface modes is numerically demonstrated while retaining the resonant frequency, and the fitting values of the plasmonic skin depth are in good agreement with theoretical values.

Ultra-wideband dual-polarized tightly coupled dipole array with double layers meta-WAIM

An ultra-wideband dual-polarized tightly coupled dipole array (TCDA) with 10:1 bandwidth is presented. Aimed at solving the ultra-wideband impedance matching problem between the antenna and free space, a novel meta-material wide-angle impedance matching (WAIM) layer is presented. The meta-WAIM utilized a structure of planar double layers with the elliptical split ring on top and the concentric split ring on the bottom, which improves the beam scanning ability over the high-frequency band. The dual-polarized dipoles are arranged as “egg-create” and fed by the integrated double-Y balun. A resistive frequency selective surface (FSS) is loaded between the dipole and ground plane to improve the active VSWR and lower the overall profile, simultaneously. The proposed antenna array can operate over a 10:1 bandwidth (0.2–2 GHz) with an active VSWR < {2.1, 2.7, 4} and average radiation efficiency > {71.6 %, 68.9 %, 60.3 %} for the scan up to {broadside, 45°, 60°}, respectively. The overall antenna profile is 95 mm, which is only 0.063λL evaluated at the lowest operating frequency. A prototype of a 6 × 10 array is simulated, fabricated, and measured. Good agreement is achieved between the simulated and measured results.

A Novel Compact High Gain Wide-Band Log Periodic Dipole Array Antenna for Wireless Communication Systems

This paper implies a prototype for a broad-band log periodic dipole antenna (LPDA) with dimensions of 20 × 40 × 0.508 mm3 equipped with directors. The LPDA is based on Roger’s RT5880 with εr = 2.2. The 4-arms with alternative stubs constitute the LPDA, which is evenly spaced on both lines. At the substrate’s back, the 50Ω main feeder line is placed on partial ground. The directors are also incorporated and studied in a regular matrix at a predetermined distance to improve gain, further reduce side lobes, and widen the frequency band. The performance of the antenna covers a wide spectrum of millimeter waves ranging from 26 up to 44 GHz. The realized gain for the antenna is 8.97, 11.96, 13.96, and 14.29 dB at 28 GHz, 35 GHz, 38 GHz, and 43 GHz, respectively. The total gain is 14.29 dB as a peak gain. The antenna was designed and tested for 5G communication applications in autonomous vehicles, and the design cost for the antenna is low in comparison to dielectric lenses. The model exhibits symmetrical radiation patterns for the antenna range. The results of the simulations and the testing of the implemented antenna elements coincide quite well. The proposed design outperforms earlier work in this field.

Wideband and Ultrathin 2×2 Dipole Array Antenna for 5G mmWave Applications

This letter proposes a wideband (24–40 GHz) and ultrathin (0.76 mm) 2×2 dipole array antenna for fifth-generation (5G) millimeter-wave (mmWave) applications. For the ultrathin array antenna, it is a challenge to match the antenna input impedance because it usually has an extremely low value. Herein, a tightly coupled frequency selective surface is proposed to provide additional resonances, and a capacitively coupled feeding method and H-walls are employed to increase the bandwidth. Furthermore, consistent measurement results are guaranteed by vertical launch connectors, and the calibration process owing to the distortion at the connectors is briefly described. In addition, the cumulative distribution function of effective isotropically radiated power scan patterns is presented at various frequencies. Finally, the performance of the proposed array antenna is compared with those of state-of-the-art mmWave array antennas.

Optimal Angle in Bistatic Measurement for Chipless Tag Detection Improvement

This article shows the use of a bistatic reading configuration by optimizing the angle between the two antennas, which allows isolating the contribution of the radio frequency identification (RFID) chipless tag from its nearby environment, thus enhancing the reading performance of the chipless tag for short-range applications. The idea is to extract as much useful signal (relating to the tag information or tag ID) from the total signal using a dedicated bistatic reading configuration. This extraction step is implemented from a hardware point of view, which is different from classical approaches based on signal processing. Indeed, based on this technique, it is possible to read tags even in highly reflective environments (metallic surfaces) without applying a calibration method, such as subtracting the environment without the tag or advanced postprocessing steps. For this purpose, a bistatic antenna configuration is employed, where the angle between the incident wave and the backscattered signal is chosen to maximize copolarization configuration. First, a model based on the general scatter theory is evaluated; it highlights the scattering mechanism involved in the problem. Then, a proof of concept (PoC) is evaluated, and afterward, a chipless tag composed of an array of dipoles is studied for identification purposes. The analytical evaluation and the channel modeling allow a general implementation of the proposed technique. Anechoic and real scenario measurements are evaluated considering the presence of surrounding objects. Finally, nonsystematic errors related to the positioning of the tag are considered each time without considering a reference (or background) measurement or the use of specific signal processing techniques.

An Effective Optimization Methods for the Suppression of Edge Effects in Ultrawideband Tightly Coupled Antenna Arrays

An effective optimization method is proposed for the suppression of edge effects in finite ultrawideband tightly coupled antenna arrays (TCAAs). By designing a practical finite TCAAs, the influences of edge effects on active voltage standing wave ratio (VSWR) are analyzed. Meanwhile, both the active VSWR and the array gain pattern are formulated as analytical expressions with respect to amplitude and phase excitations for analyzing the design freedom of edge effects. Aimed at suppressing the edge effects within an ultrawideband operation band, a nonconvex optimization problem is established for the synthesis of tightly coupled dipole arrays (TCDAs), where array gains at considered scanning angles and frequencies satisfying given maximum active VSWR and amplitude dynamic range ratio (DRR) are maximized. The nonconvex problem is transformed into an iterative convex optimization problem by the use of an iterative way, and the amplitude and phase excitations are efficiently solved by the convex optimization algorithm accordingly. By comparing to the traditional uniform amplitude and progressive phase excitation (UAPPE) method, the simulated and measured results of the ultrawideband TCDA show that the proposed method can slightly improve array gains at most frequencies, while the active VSWRs are suppressed to 3 over a 10:1 bandwidth when scanning up to 45°.

Design and Analysis of LPDA Fed Parabolic Reflector Antenna

In this research, a parabolic reflector antenna fed by a log-periodic dipole array (LPDA) was designed for the broadband requirement in the space very long baseline interferometry (SVLBI) project. Geometric parameters for LPDA and reflector were calculated and selected based on the major performance indicators, then the simulation and results were obtained in the software ANSYS Electronics 2021. The realized antenna gain exceeded the engineering requirement of 15 dB, and related issues were also studied and analyzed.

Stochastic Quantification of Array Antennas With Random Feeding Errors Using an Improved Polynomial Chaos Expansion Method

Electromagnetic properties of an array antenna are inevitably affected by random magnitude and phase errors in the feeding network. Polynomial chaos expansion (PCE) method can analyze such problems, but the number of numerical quadrature grows rapidly with stochastic dimensionality for solving the PCE coefficients. An improved PCE algorithm is proposed to improve the computational efficiency. A large array is decomposed into several small groups those can be efficiently treated by the PCE method. Stochastic quantification of the whole array is achieved by the superposition of grouped results. In addition, the proposed method can integrate with the method of moments to treat real-world arrays. The results computed by this method agree with those of Monte Carlo, and the computational time is reduced by two orders of magnitude for a dipole array with 64 elements.

Conical Conformal Tightly Coupled Dipole Arrays Co-Designed With Low-Scattering Characteristics

Conformal designs and scattering reduction have long been significant challenges to ultrawideband phased arrays. In this work, a conical conformal tightly coupled dipole array (TCDA) with low-scattering characteristics is developed. The design procedure from a planar antenna element to a two-dimensional (2-D) conformal finite array is presented in detail. In this design, a novel structure of conformal resistive strips is used as a cover layer for the radiating dipoles to control scattering, and its ability to control scattering is insensitive to variations in the dimensions of the designed conformal array. To achieve a wide scanning range and reduce scattering in a wide band, a metasurface composed of full-split rings is employed as the superstrate. The final designed array achieves a 3:1 impedance bandwidth for scanning up to ±60° in two principal planes. Moreover, scattering is reduced by more than 10 dB throughout the entire operating band. Finally, an array prototype is fabricated and measured. Measured results are in good agreement with the simulated results, thus demonstrating the effectiveness of the proposed array.

A low scattering tightly coupled dipole array based on frequency-selective polarization converter

In this paper, a low radar cross section (RCS) tightly coupled dipole array (TCDA) based on novel dual-polarized frequency-selective polarization converter (FSPC) has been proposed. The proposed FSPC structure is comprised of a polarization conversion metasurface and a band-pass frequency selective surface, and the coding sequence of FSPC can be derived by simulated annealing algorithm to achieve simulated mono-static RCS reduction. The process of the co-design of the TCDA with FSPC is presented, and the radiation performance of the antenna array meets the design requirements. A TCDA sample and 20 × 20 FSPC elements were designed and fabricated. The measured results indicated that a significant reflection reduction from 15 GHz to 21 GHz compared with a metallic plane of the same size at the boresight, and the simulated and measured normalized radiation patterns are in good agreement.