Dipole Length Research Articles

Optimal LTE-Protected LPDA Design for DVB-T Reception Using Particle Swarm Optimization With Velocity Mutation

A near-optimal design of a log-periodic dipole array (LPDA), suitable for digital video broadcasting-terrestrial (DVB-T) reception (470–790 MHz), is presented. The LPDA is required to provide low standing wave ratio as well as high-gain radiation pattern with sufficient gain flatness over the entire passband, and concurrently achieve low gain for frequencies above 800 MHz to reject LTE800 signals and thus improve the reception quality in the DVB-T band. All the above requirements are better satisfied by applying a novel particle swarm optimization (PSO) variant, called PSO with velocity mutation (PSOvm). PSOvm induces mutation on the velocities of those particles, which are unable to improve their fitness. As shown in this paper, PSOvm comes closer to the above requirements compared to four well-known optimization methods and outperforms the traditional LPDA design method proposed by Carrel. The LPDA geometry chosen for optimization is not the conventional one, and therefore the dipoles are not considered to be included inside a specified angle as proposed by Carrel. Thus, the dipole lengths and distances as well as the boom dimensions are independently optimized. The PSOvm-based LPDA sufficiently meets all the above requirements and thus is suitable for DVB-T reception without the use of an external LTE-band rejection filter.

A Singular Integral Equation for the Current Density on the Surface of a Strip Dipole in the Free Space

The problem of current density distribution over the surface of a strip dipole antenna occurring in the free space is reduced to a singular integral equation with the Cauchy singularity. Patterns of current distribution on the antenna surface for various values of the dipole length are presented.

Printed log‐periodic trapezoidal dipole array antenna with a balun‐feed for ultra‐wideband applications

The authors present design of a printed log-periodic trapezoidal dipole array (PLPTDA) antenna with a balun-feed operating throughout the 2-18 GHz frequency range. For this purpose, the antenna is designed and simulated in the CST Microwave Studio environment. Thus, better directivity along the operation bandwidth is achieved via the iterative simulations with a 33.33% reduction in the dipole length at the lowest frequency 2 GHz as compared with the counterpart standard log-periodic antennas. Furthermore, they fabricated the PLPTDA antenna with and without the balun-feed. Thus, influence of the balun on the performance is investigated and the average gain of the PLPTDA antenna with the balun-feed is measured as 8.16 dBi provided voltage standing wave ratio (VSWR) <; 2, which agrees with the simulation results. Furthermore, these measured gain/directivity results are compared with the counterpart antennas' measured performances in the literature considering their operation bandwidths and sizes. It can be concluded that their proposed PLPTDA antenna will prove to be useful in both wideband civilian and military applications in the S, C, X, and Ku bands within the 1:9 ultra-wideband bandwidth which is the largest achieved in this class antenna technology in the literature up to now.

Сингулярное интегральное уравнение для плотности тока на поверхности полоскового вибратора, расположенного в свободном пространстве

AbstractThe problem of current density distribution over the surface of a strip dipole antenna occurring in the free space is reduced to a singular integral equation with the Cauchy singularity. Patterns of current distribution on the antenna surface for various values of the dipole length are presented.

New luminescent copper(I) complexes with extended π-conjugation

While copper(I)-bis(diimine) complexes [CuI(L)2]+ are considered as potent substitutes for [RuII(bpy)3]2+, they exhibit low molar extinction coefficients with respect to ruthenium parent analogues. One interesting possibility to improve the light collection ability of [CuI(L)2]+ consists in increasing the length of the Cu-L dipole. In order to achieve this goal, we propose in this contribution to fuse aromatic rings onto the 2,9-di-nbutyl-1,10-phenanthroline core and examine how the properties of the corresponding copper(I) complexes are impacted. Electrochemical, absorption and emission properties are assessed; rewardingly, the envisioned approach was successful since extinction coefficients above 10,000 M−1·cm−1 were measured. All copper(I) complexes remain photoluminescent, with emission maxima greatly varying from 725 to 815 nm, strongly affected by the molecular structures. A rationale to explain the variations of the emission quantum yields is proposed.

Defect-Induced Wetting Behavior on Solid Polar Surfaces with Small Charge Dipole Length

Previous work showed that solid polar surfaces with a very small dipole length still might be quite hydrophobic even with large values of charge. Using molecular dynamics simulations, we have found that the presence of the point defects on a solid polar surface greatly influences the wetting behavior of water, even at a very low defect ratio of 1%. As the defect ratio increases, the coverage of the water layer over the solid surface also increases. Because of the breakdown of steric exclusion, the water molecules strongly bind to the solid surface mainly through electrostatic interactions between their hydrogen atoms and the negative charges near the positive-vacancy defects on the surface, or between their oxygen atoms and the positive charges near the negative-vacancy defects.

Broadband reflectarray composed of gap coupled elements with linear phase response

ABSTRACTA broadband reflectarray using gap coupled elements composed of a split ring and a dipole is proposed. The phase variation range of the reflected field from the element on a single layer is achieved larger than 418° by changing the dipole length in a split ring of a fixed size. The phase response of the field is proportional to the dipole length with a slow slope. Compared with multilayer elements and aperture coupled elements, it shows good linear phase response of the reflected field. To validate the proposed geometry, a prototype reflectarray is fabricated and measured. The maximum gain is 33.0 dB, and the 3 dB gain bandwidth is 19.0% at the center frequency of 20 GHz. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:1045–1047, 2017

Gravity

Considering two balls of Z protons each near each other the residual electric potential V is calculated. Also the gravitational potential is calculated. The Gravitational constant is the same for both. Thus the electric field creates gravity. This calculation is possible because the multibody energy states are known exactly. The relativistic correction of 2 has been found from the Klein-Gordon Equation solution. This finding is an important step in reducing known forces to one field. Recall the electric field is generated by motion in the magnetic field of atoms of a magnetic dipole. The mass is a function of the length of the magnetic dipole.

A Wideband Dual-Polarized Antenna With Two Independently Controllable Resonant Modes and Its Array for Base-Station Applications

A wideband dual-polarized antenna with two independently controllable resonant modes for 2G/3G/4G bands is proposed. Its radiator mainly consists of two crossed stepped-width loop dipoles loaded with two crossed straight dipoles. Two approaches are adopted to design the proposed antenna with large freedom. First, by replacing the traditional uniform-width loop dipole with a stepped-width one, the first resonant mode can be adjusted independently by controlling the width ratio of the loop. Second, a pair of crossed straight dipoles are embedded into the gap of the crossed loop dipoles, and the second resonant mode can be controlled independently by altering the length or position of the straight dipoles. Measurements show that the antenna achieves an impedance bandwidth of 54.5% with VSWR< 1.5 (1.68–2.94 GHz) and isolation of greater than 28.5 dB within the bandwidth. Also, an antenna array with ten elements is developed with electrical downtilt from 0° to 8° for practical base-station applications.

Design of Novel Broadband Endfire Dipole Array Antennas

A novel broadband endfire dipole array antenna is presented in this letter. With a novel impedance matching method, this antenna is realized as a series-fed structure and four dipole elements on the same printed circuit board. The bandwidth of the antenna is increased by staggered tuning of the dipole elements. The measured results show that the antenna has an impedance bandwidth of 70.5% for voltage standing wave ratio ( $\mathrm{VSWR)} , a gain of 3.43–6.78 dBi and endfire radiation pattern. The total size is $0.595\times 0.977\; \lambda _o^2$ ( $\lambda _o$ is the free-space wavelength at the center frequency). The studies of the dipole length and distributed capacitor are also performed to verify the design theory. The advantages of broad bandwidth and unidirectional radiation pattern make this antenna favorable in wireless communication systems.

Comparison of different sets of array configurations for multichannel 2D ERT acquisition

Traditional electrode arrays such Wenner-Schlumberger or dipole-dipole are still widely used thanks to their well-known properties but the array configurations are generally not optimized for multi-channel resistivity measures.Synthetic datasets relating to four different arrays, dipole-dipole (DD), pole-dipole (PD), Wenner-Schlumberger (WS) and a modified version of multiple gradient (MG), have been made for a systematic comparison between 2D resistivity models and their inverted images. Different sets of array configurations generated from simple combinations of geometric parameters (potential dipole lengths and dipole separation factors) were tested with synthetic and field data sets, even considering the influence of errors and the acquisition velocity. The purpose is to establish array configurations capable to provide reliable results but, at the same time, not involving excessive survey costs, even linked to the acquiring time and therefore to the number of current dipoles used.For DD, PD and WS arrays a progression of different datasets were considered increasing the number of current dipoles trying to get about the same amount of measures. A multi-coverage MG array configuration is proposed by increasing the lateral coverage and so the number of current dipoles. Noise simulating errors both on the electrode positions and on the electric potential was added.The array configurations have been tested on field data acquired in the landfill site of Bellolampo (Palermo, Italy), to detect and locate the leachate plumes and to identify the HDPE bottom of the landfill.The inversion results were compared using a quantitative analysis of data misfit, relative model resolution and model misfit. The results show that the trends of the first two parameters are linked on the array configuration and that a cumulative analysis of these parameters can help to choose the best array configuration in order to obtain a good resolution and reliability of a survey, according to generally short acquisition times.

Ionospheric influence on the seismo-telluric current related to electromagnetic signals observed before the Wenchuan &amp;lt;i&amp;gt;M&amp;lt;/i&amp;gt;&amp;lt;sub&amp;gt;&amp;lt;i&amp;gt;S&amp;lt;/i&amp;gt;&amp;lt;/sub&amp;gt; 8.0 earthquake

Abstract. A three-layer (Earth–air–ionosphere) physical model, as well as a two-layer (Earth–air) model, is employed in this paper to investigate the ionospheric effect on the wave fields for a finite length dipole current source co-located at a hypocenter depth and along the main fault of an earthquake when the distance between the epicenter and an observing station is up to 1000 km or even more. The results show that all electrical fields are free of ionospheric effects for different frequencies in a relative short range, e.g., ∼ 300 km for f = 1 Hz, implying the ionospheric influence on electromagnetic fields can be neglected within this range, which becomes smaller as the frequency increases. However, the ionosphere can give a constructive interference to the waves passing through and make them decay slowly when an observation is out of this range; moreover, the ionospheric effect can be up to 1–2 orders of magnitude of the electrical fields. For a ground-based observable 1.3 mV m−1 electric signal at f = 1 Hz 1440 km away from the Wenchuan MS 8.0 earthquake, the expected seismo-telluric current magnitude for the Earth–air–ionosphere model is of 5.0 × 107A, 1 magnitude smaller than the current value of 3.7 × 108A obtained by the Earth–air model free of ionospheric effects. This indicates that the ionosphere facilitates the electromagnetic wave propagation, as if the detectability of the system were improved effectively and it is easier to record a signal even for stations located at distances beyond their detectability thresholds. Furthermore, the radiating patterns of the electrical field components |Ex| and |Ey| are complementary to each other, although any two-dimensional (2-D) power distribution of these components shows strong power areas as well as weak ones, which is advantageous to register a signal if the observing system is designed to measure both of them instead of only one.

Miniaturized band‐notched ultra‐wideband antenna

ABSTRACTA miniaturized band‐notched ultra‐wideband antenna with a bandwidth from 2.7 to 13.1 GHz (i.e., bandwidth ratio 4.9:1) for VSWR ≤ 2 and a stop band from 5 to 6 GHz is designed and optimized. The overall area is reduced by 30% and a radiation rejection band is engineered by inserting a 1/2 wavelength thin strip dipole to serve as an anti‐resonator in the undesired band where the radiated field from the radiator is phase‐reversed with respect to that from the inserted anti‐resonator, consequently the total radiation is cancelled out, and the stop band can be easily tuned by adjusting the dipole length and width. It is shown that this antenna is robust in rejecting environmental interferences. A prototype of this antenna is fabricated and measured. The measurements agree well with the simulation results.© 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2780–2786, 2016

Comparison of evolutionary algorithms for LPDA antenna optimization

AbstractA novel approach to broadband log‐periodic antenna design is presented, where some of the most powerful evolutionary algorithms are applied and compared for the optimal design of wire log‐periodic dipole arrays (LPDA) using Numerical Electromagnetics Code. The target is to achieve an optimal antenna design with respect to maximum gain, gain flatness, front‐to‐rear ratio (F/R) and standing wave ratio. The parameters of the LPDA optimized are the dipole lengths, the spacing between the dipoles, and the dipole wire diameters. The evolutionary algorithms compared are the Differential Evolution (DE), Particle Swarm (PSO), Taguchi, Invasive Weed (IWO), and Adaptive Invasive Weed Optimization (ADIWO). Superior performance is achieved by the IWO (best results) and PSO (fast convergence) algorithms.

Quasistatic dipole in magnetized plasma in resonance frequency band. Response of the receiving antenna, and charge distribution on the antenna wire

The paper discusses issues related to the radiation and reception of quasi-electrostatic waves by short antennas in resonance conditions (in the whistler range) in magnetized plasma. First, the response of the receiving antenna on the incident field of slow quasipotential waves is analyzed. It made it possible to explain in detail the results of the two-point rocket experiment OEDIPUS-C in the Earth’s ionosphere. Second, the problem of the charge distribution along the short transmission (reception) dipole antenna is considered. The corresponding integral equation is obtained and solved analytically. The impedance of the antenna is found. It is shown that in the majority of cases, charge distribution along the dipole length can be considered constant.

Theoretical photoionization processes for aluminum-like P2+

The theoretical photoionization cross sections for the ground and metastable states of Al-like P2+ are first time investigated in the photon energy range of 30–43.5 eV by the Dirac R-matrix method, and a good agreement between the dipole length and velocity form is achieved. The effects of the partial photoionization on the total PI of ground and metastable states are discussed. Our theoretical results are consistent with the latest experimental measurement, only some discrepancies are found. The channel coupling effects play an important role in the photoionization of Al-like P2+. The resonance energies and quantum defects are obtained, where a comparison between the theoretical and experimental data is made. It is worth noting that the theoretical resonance is as large as 0.28 eV. Our results can serve as a reference to further study the PI of Al-like P2+ in theory and experiment and be regarded as a supplement for Opacity Project TOP base results.

Dipole analysis of the influence of linear arrays of points on visually perceived eye level (VPEL)

Previous research has shown that a visual field consisting of as little as one peripherally located luminous line that is pitched from vertical in a dark field induces large changes in an observer’s visually perceived eye level (VPEL). The effects of this severely reduced inducing stimulus are surprisingly close to the effects of a highly structured pitched visual field. In the present report we describe two experiments with inducing stimuli that were still further reduced to one or two linear arrays of points of light. The results show that the array’s effect on VPEL increases as a negatively accelerated increasing function of the amount of stimulus (i.e., the length of the array, the number of points, and the interpoint separation). We propose a multiscale dipole model (MDM), which quantifies the effect of the array of points on VPEL in terms of dipoles of various lengths that activate orientation and size specific neurons in visual cortex. For example, when the number of points increases in an array of fixed length, dipoles of progressively shorter length are created within the overall length of the stimulus. The shorter dipoles stimulate additional orientation-selective neurons with smaller receptive fields whose neural activity adds to the activity generated by the larger dipoles up to a saturation limit. The functional relation between the psychophysical response and the number of dipoles can be modeled as a rectangular hyperbola, formally similar to equations that have been used to model saturation binding and enzyme velocity in biochemistry and contrast response functions in neurophysiology and psychophysics.

A Compact Microstrip-Fed Planar Dual-Dipole Antenna for Broadband Applications

We present a broadband end-fire planar circuit antenna that is suitable for applications in microwave, millimetre (mm) and sub-millimetre (sub-mm) wavelengths. We have cascaded two dipoles of different lengths in series to broaden the bandwidth. Two printed directors and a truncated ground plane are used to achieve high front-to-back (F/B) gain ratio. The parallel stripline feeding the antenna’s drivers is connected directly to microstrip without an intermediate stage. This simple antenna design is easily integrated into microstrip circuits. In this paper, we focus on the design of a Ku-band antenna with 7 GHz bandwidth and F/B gain ratio of 18 dB. Design and analysis of the antenna were performed using rigorous electromagnetic simulations, and we experimentally validated the performance of the antenna by measuring the beam patterns and return loss of an antenna fabricated on a Roger RO 4350 printed circuit board. Finally, we present two unique example applications of the antenna in the sub-mm detectors area.

Input impedance and radiation pattern of a resonant dipole embedded in a two‐dimensional periodic leaky‐wave structure

Array scanning method (ASM) is employed to study the input impedance and radiation pattern of a two-dimensional periodic leaky-wave antenna (LWA). The antenna consists of a narrow horizontal strip dipole of arbitrary length underneath a two-dimensional (2D) periodic screen of metallic patches, which acts as a partially reflective surface (PRS), and backed by a ground plane. First, the Green's function in the presence of the 2D array of metallic patches is calculated by means of the ASM and then the current distribution and input impedance of the source dipole are calculated through the electric field integral equation and method of moments. The far-field pattern is computed using the reciprocity theorem. Compared to the Hertzian dipole, which is the only type of source that has been considered in the literature, the resonant dipole substantially improves the performance of periodic LWA in terms of radiated power, efficiency and bandwidth. Numerical results are given for a resonant dipole over the frequency range of 60-70 GHz and compared with those obtained from commercial softwares, FEKO ® and Ansys HFSS ® , showing an excellent agreement with considerable improvement in terms of memory usage and computational speed.

Two types of marine controlled source electromagnetic transmitters

ABSTRACTMarine controlled source electromagnetic methods are used to derive the electrical properties of a wide range of sub‐seafloor targets, including gas hydrate reservoirs. In most marine controlled source electromagnetic surveys, the deep‐tow transmitter is used with a long horizontal electric dipole being towed above the seafloor, which is capable of transmitting dipole moments in the order of up to several thousand ampere‐metres. The newly developed deployed transmitter uses two horizontal orthogonal electrical dipoles and can land on the seafloor. It can transmit higher frequency electromagnetic signals, can provide accurate transmission orientation, and can obtain higher signal stacking, which compensates for the shorter source dipole length. In this paper, we present the study, key technologies, and implementation details of two new marine controlled source electromagnetic transmitters (the deep‐tow transmitter and the deployed transmitter). We also present the results of a marine controlled source electromagnetic experiment conducted from April to May 2014 in the South China Sea using both the deep‐tow transmitter and the deployed transmitter, which show that the two types of marine transmitters can be used as effective source for gas hydrate exploration.