Ratio Of Radiated Power Research Articles

A Null-Filled Axisymmetric Secant-Square-Shaped Beam Antenna for Unmanned Aerial Vehicles

In this letter, an antenna with a null-filled axisymmetric secant-square-shaped beam for the unmanned aerial vehicle (UAV) is proposed. The proposed antenna consists of four monopoles with sequentially rotated feed (SRF) and a coupling-fed grooved circular patch. The radiation power ratio of the monopoles and the patch is used to shape the axisymmetric beam. The effect of the ground is also investigated to operate positively on beam shaping. A prototype was fabricated to validate the method and the performance of the proposed antenna. The gain curves of the proposed antenna coincide well with the secant-squared (sec <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) curve from θ = 0° to θ = 60° in all azimuthal angles with root mean square error (RMSE) below 1.35 dB in 5.5 GHz - 5.7 GHz.

Influence of Spatial Selectivity of Radiation of Mobile Communication Base Stations on the Level of Electromagnetic Background Introduced by them

Radio frequency electromagnetic radiation from base stations is the main source of electromagnetic background generated by mobile (cellular) communication systems in residential areas; its intensity makes a significant contribution to the level of electromagnetic pollution of the habitat and determines the level of electromagnetic safety of the population. The previously proposed technique for estimating the average intensity of this background, based on the analysis of the territorial intensity of mobile traffic, takes into account the spatial selectivity of base station radiation in a simplified form by introducing the radiation directivity parameter U, equal to the inverse of the number of base station service sectors, assuming that the width of the main lobe of the radiation pattern is equal to the width of this sector and without taking into account the radiation directivity in the vertical plane, which determines the pessimistic nature of these estimates. The paper presents a refined analysis of the values of the parameter U for a two-level models of antenna radiation patterns, which reflects the real values of the width of their main lobes in horizontal and vertical planes, the relative levels of side lobes and the ratio of radiation power of the main and side lobes. The analysis was performed both for stationary sector antennas of cellular communication systems and for adaptive phased antenna arrays of 4G/5G systems capable of providing service using narrow beams. The analysis showed that the value of the U parameter of sector antennas is 5–15 dB less than the inverse of the number of sectors of base stations, and for narrow beams of adaptive antenna arrays, this difference reaches 20 dB. If tilt angles of main lobes of antenna radiation patterns with respect to the horizon are less than 30°, then at estimation of the average electromagnetic background intensity the inverse of their antenna gain in the main lobe can be used as the U parameter value of the spatial selectivity (directivity) of base stations radiations.

Simulation study on the enhancement of resonance energy transfer through surface plasmon coupling in a GaN porous structure

To understand the behavior of resonance energy transfer from a quantum well (donor) into a quantum dot (acceptor) located inside an oriented subsurface tubular void above the quantum well, the emission and energy transfer enhancements of the donor and acceptor dipoles are numerically studied. By reasonably assuming that the acceptor absorption efficiency is not influenced by the surface plasmon (SP) resonance of a nearby metal nanostructure, the acceptor absorption enhancement through SP coupling is proportional to the increase ratio of the donor-induced field intensity at the acceptor position. Therefore, the energy transfer enhancement can be obtained by multiplying this field intensity ratio with the radiated power ratio of the acceptor between the two cases under comparison. It is found that the emission and energy transfer enhancements are significantly higher when the orientations of the donor and acceptor dipoles are perpendicular to the void tube, in comparison with those in the case of parallel orientation. The differences in emission and energy transfer between the two dipole-orientation cases become larger when a surface Ag nanoparticle is applied to the sample for inducing SP coupling. The oriented subsurface tubular void can lead to a polarization-dependent energy transfer behavior.

Inverse-Compton scattering in the resolved jet of the high-redshift quasar PKS J1421−0643

ABSTRACT Despite the fact that kpc-scale inverse-Compton (iC) scattering of cosmic microwave background (CMB) photons into the X-ray band is mandated, proof of detection in resolved quasar jets is often insecure. High redshift provides favourable conditions due to the increased energy density of the CMB, and it allows constraints to be placed on the radio synchrotron-emitting electron component at high energies that are otherwise inaccessible. We present new X-ray, optical, and radio results from Chandra, HST, and the VLA for the core and resolved jet in the z = 3.69 quasar PKS J1421−0643. The X-ray jet extends for about 4.5 arcsec (32 kpc projected length). The jet’s radio spectrum is abnormally steep and consistent with electrons being accelerated to a maximum Lorentz factor of about 5000. Results argue in favour of the detection of iC X-rays for modest magnetic field strength of a few nT, Doppler factor of about 4, and viewing angle of about 15°, and predict the jet to be largely invisible in most other spectral bands including the far- and mid-infrared and high-energy gamma-ray. The jet power is estimated to be about 3 × 1046 erg s−1 which is of order a tenth of the quasar bolometric power, for an electron–positron jet. The jet radiative power is only about 0.07 per cent of the jet power, with a smaller radiated power ratio if the jet contains heavy particles, so most of the jet power is available for heating the intergalactic medium.

Optimal Beam Pattern Design for Hybrid Beamforming in Millimeter Wave Communications

Beamforming is an enabling technique for wireless communications over higher frequency band, e.g., mmWave frequency band. To enhance beam concentration and homogenization within any angle range, we propose a hybrid beamforming design in three steps. First, through analyzing radiation power ratio, we find the bases of beamforming vector to guarantee a satisfactory level of power radiated over the targeted angle range. Second, with the derived bases, we flat the response of the passband by solving a max-min optimization problem using semidefinite relaxation technique. Third, we perform hybrid decomposition to achieve compatibility with phased array antenna with hybrid structure. The proposed beamforming is verified through quantitative measurement of beam concentration and homogenization. Simulation results show that the beamform pattern designed by our method outperform other existing methods in multi-cell scenarios.

Analysis of Substrate Effect in Field Effect Transistor Terahertz Detectors

The development of terahertz (THz) detectors based on field effect transistors (FETs) with planar antennas requires improving the detector responsivity, thus it needs higher coupling efficiency between the antenna and THz radiation. Substrate effect and its impact on the detector responsivity have been investigated for the case of semiinfinite substrate, and four different types of planar dipole antennas are compared. The ratio ( R ) of the power radiated into the air to the total power radiated by planar antenna shows several peaks when the substrate thickness increases. Independent of antenna structure and source impedance, the ratio R would only depend on the substrate thickness, the dielectric constant of substrate, and the operation frequency. Furthermore, the simulation result shows that the radiation power ratio R is correlated with the detector responsivity. This correlation is independent of FET input impedance and antenna structure. It indicates that the ratio R can be used as a reference to choose proper substrate parameters. All the results above can be extended to common materials and broad range of frequency. The comparison of four antennas shows that besides substrate effect, the antenna design would also have a significant impact on the detector responsivity.

Gain enhancement of an electrically small antenna array using metamaterials

This paper presents the enhancement of radiated power ratio of a two-dipole array of infinitesimal dipole elements, separated by an infinitesimal distance. It is shown that a properly constructed metamaterial shell configuration with optimized material parameters surrounding the dipole can cancel both the self- and the mutual reactances of the array system. Simultaneously, a very high radiated power ratio is realized for the array system even in the presence of strong mutual coupling between the array elements. This potentially leads to the development of highly efficient ultra-compact antenna arrays. In addition, by using a material of non-unity permittivity surrounding the array system, uniform radiated power ratio characteristics can be achieved with the variation in the metamaterial shell thickness. This removes the major drawback in the practical design of the metamaterial shell proposed earlier for the radiated power ratio enhancement of a single dipole. Very good matching characteristics are obtained for the antenna configuration demonstrating almost complete cancelation of the reactive power of the array system. The frequency dispersive behavior of the antenna configuration is investigated using the lossless and lossy Drude models.

EFFICIENT ELECTRICALLY SMALL PROLATE SPHEROIDAL ANTENNAS COATED WITH A SHELL OF DOUBLE-NEGATIVE METAMATERIALS

An efficient, electrically small prolate spheroidal antenna coated with confocal double-negative (DNG) metamaterials (MTMs) shell is presented. The radiation power of this antenna-DNG shell system excited by a delta voltage across an infinitesimally narrow gap around the antenna center is obtained using the method of separation of the spheroidal scalar wave functions. Our results show that this electrically small dipole-DNG shell system has very high radiation efficiency comparing with the normal electrically small antenna due to the inductive effect of the MTMs shell that cancel with the capacitive effect of the electrically small antenna. It is found that the spheroidal shell can achieve more compact structure and higher radiated power ratio than the corresponding spherical shell. This dipole-DNG shell systems with different sizes are analyzed and discussed.

Correspondence between frequency characteristics of radiated emission and input impedance of power‐ground planes of PCB

AbstractThe frequency at the peak of electromagnetic radiation from a PCB (Printed Circuit Board) as a result of ground bounce is considered predictable from the frequency characteristics of the input impedance between the power supply and ground layer (below called the PCB impedance). However, the relationship is largely unknown. In this paper, the electromagnetic radiation of the PCB and the frequency spectrum of the PCB impedance are analyzed by the FDTD (Finite‐Difference Time‐Domain) method and their relational mechanism is studied by comparison with the measured values. It is found that the peak of the electromagnetic radiation appears at the frequency where the PCB is a minimum if the PCB is excited by a voltage source with an internal resistance sufficiently smaller than the PCB impedance, and that this peak is shifted toward the frequency at which the PCB impedance becomes a maximum if the internal resistance is increased. The radiation power ratio derived from the resistive components (called the resonant resistances) at two frequencies where the PCB impedance is maximum and minimum (resonant frequencies) mostly agrees with the ratio of the squares of the radiated electric field. Hence, the radiation peak frequencies of the PCB are determined both by the internal resistance of the excitation source and the resonant resistance of the PCB impedance. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(11): 30–38, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10209

Study of various shapes of the coupling slot in CPW-fed microstrip antennas

A numerical modeling based on the solution of coupled integral equations is used for the characterization of CPW-fed aperture-coupled microstrip antennas. Various shapes of excitation slots, such as open stubs, slot loops, and capacitively and inductively coupled slots, are investigated in terms of return loss and front-to-back radiated power ratio. It is shown that a centered CPW open stub gives a minimum of back radiation while allowing for easy matching. The slot-loop excitation seems to be a convenient feeding mechanism that also allows the insertion of active devices.

Error Performance of M-ary DPPM Communication System

Error performance in optical communication, where the information is transmitted by means of the differential pulse-position modulated optical carrier, is discussed. Additive independent background radiation and thermal noise are taken into account. Both threshold type and maximum value type of decision schemes are also considered. The effects of several parameters, such as the number of time slots, the duty ratio, the extinction ratio, the count dimension, the signal-to-background radiation power ratio, and the signal-to-thermal noise power ratio are discussed in detail. The detection characteristic of this system are made clear by comparison with a pulse-position modulation system.