Field Radiation Pattern Research Articles

Broadband Dipole-Loop Combined Nanoantenna Fed by Two-Wire Optical Transmission Line

This paper presents a broadband nanoantenna fed by a two-wire optical transmission line (OTL). The antenna is defined by a combination of a dipole and a loop, where only the dipole element is connected to the OTL. The analysis is fulfilled by the linear method of moments with equivalent surface impedance to model the conductors. Firstly, the nanoantenna alone is investigated, where the input impedance, current distribution, reflection coefficient, fractional bandwidth, radiation efficiency, and radiation pattern are analyzed. Then, the input impedance matching of this antenna with the OTL is considered. In this case the current, near field distribution, radiation pattern, and reflection coefficient are calculated for different geometrical parameters. The results show that the loop inserted in the circuit can increase the bandwidth up to 42% and decreases the reflection coefficient in the OTL to −25 dB.

Design of a Broadband Quasi-Optical Mode Converter for $W$ -Band Gyro-TWTs

Mode converters for millimeter waves can reduce the transmission loss, generate the desired mode, and facilitate the application of high-power sources. A W-band broadband quasi-optical mode converter which converts a TE0,1 cylindrical waveguide mode into a linearly polarized Gaussian TEM00 mode has been realized and tested in this paper. The converter is composed of a wavefront transforming mirror, a polarization grating, and a phase correcting system. In order to obtain high conversion efficiency over a wide bandwidth and make the structure of the mode converter much simple and compact, the propagation path of the beam is optimized and a wavefront transforming mirror realized by an ellipsoidal mirror rather than a nonquadratic mirror is introduced. The conversion process in each section is displayed and the working principles are discussed in detail. The mode conversion characteristics are investigated by analyzing the measured radiation field pattern. Results of the measurement agree well with the numerical calculations. The proposed W-band mode converter has a conversion bandwidth of 21% when the mode conversion efficiency is over 95% and the cross polarization is below 1.7%. In addition to high conversion efficiency, low cross-polarization, and broad bandwidth, this converter features easy construction and compact structure.

Design and Analysis of a Reconfigurable Holographic Metasurface Aperture for Dynamic Focusing in the Fresnel Zone

We present numerical simulations of the near-field focusing capabilities of a dynamically reconfigurable holographic metasurface aperture. The aperture consists of a parallel-plate waveguide in which the upper plate is patterned with a number of metamaterial irises that can be dynamically switched between radiating (ON) and non-radiating (OFF) states. A cylindrically symmetric waveguide mode, excited by a coaxial probe in the center of the lower plate, serves to excite the radiating irises, forming a focused spot in the radiating near-field (or Fresnel zone). The layout of the metamaterial elements and their tuning states is determined using holographic design principles, in which the interference pattern of the waveguide (or reference) mode and the desired radiated field pattern leads to the required phase distribution over the surface of the aperture. We also develop an analytical model of the aperture to confirm the numerical simulations, and to illustrate the advantage of the guided-mode as the reference wave versus a plane-wave. We further leverage this analytical model to analyze the diffracted order characteristics of the holographic metasurface aperture, showing high-fidelity focusing patterns even for difficult focusing scenarios across the entire investigated field-of-view.

Probability of Detection Functions of Polarization-MIMO Systems in Random-LOS

We derive the probability of detection functions of 1- and 2-bitstreams for polarization multiple-input multiple-output antenna systems in random line-of-sight propagation conditions. The derivations are produced assuming that the angle-of-arrival of the field impinging at the receive antenna is fixed. Hence, randomness is only due to the direction of polarization of the incident field relative to the polarization of the far-field of the receiver antenna. Also, a general analytical orthogonalization transformation matrix has been derived for far-field functions of arbitrary dual-polarized antennas and used in the probability of detection derivations. Analytical results are obtained for the maximum ratio combining receiver diversity and the zero-forcing multiplexing receiver algorithms. These results provide a practical prediction tool of the impact of antennas on system performance due to polarization deficiencies of analytical, measured or simulated radiation field patterns of dual polarized antennas. This is illustrated by the provided numerical examples.

Modeling of absorption and scattering properties of core -shell nanoparticles for application as nanoantenna in optical domain

The present paper describes the study of core-shell nanoparticles for application as nanoantenna in the optical domain. To obtain the absorption and extinction efficiencies as well as the angular distribution of the far field radiation pattern and the resonance wavelengths for these metal-dielectric, dielectric-metal and metal-metal core-shell nanoparticles in optical domain, we have used Finite Element Method based COMSOL Multiphysics Software and Mie Theory. From the comparative study of the extinction efficiencies of core-shell nanoparticles of different materials, it is found that for silica - gold core - shell nanoparticles, the resonant wavelength is greater than that of the gold - silver, silver-gold and gold-silica core - shell nanoparticles and also the radiation pattern of the silica-gold core-shell nanoparticle is the most suitable one from the point of view of directivity. The dielectric functions of the core and shell material as well as of the embedded matrix are extremely important and plays a very major role to tune the directivity and resonance wavelength. Such highly controllable parameters of the dielectric - metal core - shell nanoparticles make them suitable for efficient coupling of optical radiation into nanoscale structures for a broad range of applications in the field of communications.

Four element half circle shape printed mimo antenna

ABSTRACTIn this work, a four element multiple‐input‐multiple‐output (MIMO) antenna system with half circle shape printed monopole antennas is presented. The antenna elements are designed on an FR4 substrate with dielectric constant 4.3 and dimensions of 110 × 60 × 0.8 mm3. These antennas are covering part of 4G and WLAN bands with maximum measured gain and efficiency of 3.12 dB and 81.5%, respectively, along with a −10 dB bandwidth of 230 MHz. The coupling between adjacent ports is at least −11 dB without using any technique for isolation enhancement. The MIMO antenna system has good pattern isolation such that the correlation coefficient is calculated using the measured three‐dimensional (3D) far field radiation pattern with a maximum value of 0.3 at 2.4 GHz. The proposed design can be used in handheld terminals. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2990–2992, 2016

New Subwavelength Profile Monopole-Type Antenna

In this paper, we present a new low-profile ( $\lambda $ /40) compact antenna for the S-band frequency range (around 2.1 GHz). The main features are high efficiency (>90%), vertical polarization, and omnidirectional radiation patterns. The antenna was designed using a low-profile vertical monopole element with a standard metallic reflector plane. Top-loading techniques with symmetrical coplanar folded-slot dipoles ( $\lambda _{g}$ /2) and four vertical shorting pins placed at appropriate locations achieved the desired antenna matching impedance-bandwidth. The overall dimension of the antenna is $0.32\lambda \times 0.32\lambda \times 0.025\lambda $ . A prototype of the designed antenna was fabricated and fully characterized. The experimental results are in good agreement with the numerical calculations. The measured field radiation patterns are similar to those of standard vertical monopole antenna with a maximum normalized gain of 3.7 dB at 2.1 GHz and a bandwidth of 5% ( $S_{11} dB).

A compact microstrip-fed open slot antenna for dual slant polarization with good isolation

A V-shape slot antenna for dual slant polarization is proposed. The slot is the union of two stepped rectangular slots tilted at ±45° with the vertical. Each section of the slot is excited using a microstrip feed line printed on the other side of the substrate. The feed is also stepped and bent so as to cross the slot at right angles. The decoupling between the ports is provided by means of narrow rectangular stubs placed at the intersection of the slot arms. Measurements taken on the fabricated prototype indicate an impedance bandwidth from 3.3 to 12 GHz with isolation better than 15 dB across the band. The aperture electric field distributions as well as far field radiation patterns are used to verify the dual slant polarization achieved with the antenna. The time domain characterization of the antenna is done by calculating the fidelity factor which is found to be >0.75 indicating suitability of the antenna for pulse transmission. For determining the diversity behavior, the envelope correlation coefficient is calculated and found to be below 0.004. The antenna has a peak gain from 4 to 6 dBi. A modified design of the antenna is also presented with impedance bandwidth from 3 to 12 GHz and isolation better than 20 dB from 3.7 GHz onwards. With compact features and wideband return loss and isolation, the antennas are expected to be useful for diversity applications in ultra wideband communication devices such as MIMO wifi, imaging radars, and polarimetric sensing devices.

Transmission-Line Model of Nonuniform Leaky-Wave Antennas

Nonuniform leaky-wave antennas (LWAs) are analyzed and synthesized using a lossy transmission line model. The analysis is based on a general waveguide circuit theory. Compared to the classical approach, the model yields a higher accuracy in the computation of both aperture field distribution and radiation patterns. The proposed analysis is also able to provide scattering parameters of the whole structure in a fraction of a second, which is valuable for antenna optimization. Based on the analysis, a general method for far-field pattern synthesis utilizing global optimization is presented. As an application demonstration, the half-mode substrate-integrated waveguide (HMSIW), or half-width microstrip line, has been selected as basis structure for the LWA designs. Two antennas have been optimized targeting different specifications, i.e., a low-sidelobe level and a wide null in the radiation pattern. Experimental results are provided for these selected examples of nonuniform LWAs, which ultimately validate the proposed technique as an improvement over the classical approach.

Investigation of spherical and cylindrical Luneburg lens antennas by the Green's function method

Luneburg lens antenna radiation fields are calculated with Green's functions of spherical and cylindrical layered structures. Electric field components of spherical and cylindrical Luneburg lenses excited by linear and circular polarized incident field are analysed. Dipole, slot and aperture antennas are described by electric and magnetic extraneous currents. Radiation patterns of cylindrical and spherical Luneburg lens are analysed. Co-polarized and cross-polarized field radiation patterns are shown. The proposed method significantly reduces the computing time for multi-layered lenses in comparison with the most commonly used in antenna design. The first step antenna structure optimization may be performed for a shorter time. The results may be used as the first approximation for Ansys HFSS and other software.

A study on the multi-antenna geometrical depolarization channel modeling

The traditional geometrical depolarization model that single transmitter to single receiver provides a simple method of polarization channel modeling. It can obtain the geometrical depolarization effect of each path if known the antenna configuration, the polarization field radiation pattern and the spatial distribution of scatters. With the development of communication technology, information transmission spectrum is more and more scarce. The original model provides only a single channel polarization state, so the information will be limited that the polarization state carries in the polarization modulation. The research is so significance that how to carries polarization modulation information by using multi-antenna polarization state. However, the present study shows that have no depolarization effect model for multi-antenna systems. In this paper, we propose a multi-antenna geometrical depolarization model. On the basis of a single antenna to calculate the depolarization effect of the model, and through simulation to analysis the main factors that influence the depolarization effect. This article provides a multi-antenna geometrical depolarization channel modeling that can applied to large-scale array antenna, and to some extent increase the speed of information transmission.

Broadband mode division multiplexer using all-fiber mode selective couplers.

We report an all-fiber mode division multiplexer formed with cascaded mode selective couplers with significantly broadened bandwidth potentially spanning S, C and L band. This was achieved by matching the effective refractive indices over a wide wavelength range for the few mode fiber and the single mode fiber used in the coupler. The multiplexer provides high coupling efficiency (>55% for the worst case) for the 4 spatial modes over the entire wavelength range of 1515-1590 nm. The all-fiber construction provides mechanical stability. Experimental results for the coupling efficiency and the mode extinction ratio for each spatial mode are presented along with the far field radiation patterns.

Installed Performance Assessment of Blade Antenna by means of the Infinitesimal Dipole Model

This paper presents an accurate and simple model to predict the radiation pattern of a blade antenna installed on an aircraft. Based on the far field radiation pattern of the blade antenna on a ground plane, an equivalent infinitesimal dipole model (IDM) is built. Taking into consideration the basic geometry and some physical characteristics of the antenna to be modeled, the proposed approach has overcome one of the major problems of the classic IDM by reducing the number of parameters to be optimized. In order to validate its application in electromagnetic large structures problems, an aircraft is chosen as a case study. Good agreement with the radiation patterns is obtained between the proposed model and a blade antenna, where its accuracy and reduction in computational cost is verified.

Experimental validation of a transformation optics based lens for beam steering

A transformation optics based lens for beam control is experimentally realized and measured at microwave frequencies. Laplace's equation is adopted to construct the mapping between the virtual and physical spaces. The metamaterial-based lens prototype is designed using electric LC resonators. A planar microstrip antenna source is used as transverse electric polarized wave launcher for the lens. Both the far field radiation patterns and the near-field distributions have been measured to experimentally demonstrate the beam steering properties. Measurements agree quantitatively and qualitatively with numerical simulations, and a non-narrow frequency bandwidth operation is observed.

Dielectric loaded tm<sub>01</sub> to te<sub>11</sub> mode converter for S-band applications

In this paper, a compact, high efficiency TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> to TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode converter is presented. In the proposed structure, dielectric material is loaded below a tapered centre conductor, in lower section of a circular waveguide. The input TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> mode is initially transformed to TEM mode by the tapered centre conductor. The loaded dielectric material is designed to provide the desired phase shift for the mode conversion. Different dielectric materials are analyzed for loading to achieve high conversion efficiency and wide bandwidth. The proposed mode converter is fabricated with PTFE as dielectric for mode conversion and the results are verified through far field radiation pattern measurements. The mode conversion efficiency is more than 90% for 2.95-3.60 GHz band. Due to compactness and high conversion efficiency for wide bandwidth, it is suitable for S-band high power microwave (HPM) applications.

Design and investigations of a microstrip fed open V-shape slot antenna for wideband dual slant polarization

A dual slant polarized slot antenna is proposed. The antenna is printed on the two sides of a single substrate and has two microstrip feed lines to excite a V-shaped slot formed by the merging of two tilted rectangular step shaped slots. Stepping of the slot sections as well as the feed line improves the impedance matching. A narrow rectangular metallic stub is introduced at the junction of the slot arms to improve the decoupling between the ports. The antenna polarization is +450/−450 with respect to horizontal under alternate excitation and this dual slant polarized nature is demonstrated through aperture electric field plots and far field radiation patterns. The measured return loss bandwidth (S11 < −10 dB) of the antenna is from 2.3 GHz and extends beyond 12 GHz while the measured isolation bandwidth (S21 < −20 dB) is from 5 GHz onwards. The time domain characterization of the antenna is also done by calculating the fidelity factor. For evaluating the diversity performance, the envelope correlation coefficients are calculated from the simulated and measured S-parameters. The correlation coefficients are well below the acceptable values. With a peak gain varying between 3 and 5 dBi, the antenna is expected to be useful for wideband dual slant polarized applications.

Multiple-unit antennas on paraboloidal lattices of dielectric resonators

Introduction. Today a multiple-unit antenna properties, containing big number DRs are studied inefficiently. At present article a possibility of the antennas building produced on paraboloidal lattices consisting DRs of the cylindrical form with lowest magnetic type resonances is considered. The results. Calculation results of the antenna parameters on dielectric resonator paraboloidal lattices are presented. The space distribution of the radiation field patterns in the near and wave zones is considered. Reflection coefficient frequency dependence of the antennas is calculated. Possibility narrowing of the directional pattern is showed. Signals frequency selection performing as well as increased electromagnetic compatibility of the suggested structures is noticed. Conclusion. Adduced calculations indicate capability of the practical application lattices on DRs as well as building on their base a wide class of the frequency selective antennas in millimeter and sub millimeter wavelength ranges. Such antennas will have enhanced electromagnetic compatibility.

Phased-array beam steering using optical true time delay technique

An optical dispersion technique for phased-array beam steering is proposed and analyzed. Optical true time delay using a high-dispersion compensation fiber (HDCF) and a phased array antenna (PAA) can provide a continuous radio-frequency squint-free beam scanning. When the dispersion of the fabricated DCF-C band is as high as −1020±31ps/nm/km, the laser wavelength can be tuned from 1549.95 to 1550.2nm. The experimental results confirmed that the scanning angle of far field radiation patterns for proposed technique can be tuned to have a range 51° (from −22° to +29° ) at frequency of 5.9, 12.7 and 17GHz.

English

The far field radiation pattern from a parabolic reflector depends on the primary radiation pattern which is the radiation pattern of the feed element placed and also on the type and dimensions of reflector used. Therefore in this paper analysis of the E-plane and H-plane normalized radiation patterns in dB by using MATLAB programming 2010a. In addition the beam width and efficiency patterns for different center frequencies, focal lengths and diameters were also calculated. A parabolic reflector has been picked as the reflector because it produces high gain pencil beam with small side lobes. Using aperture approximation methods the radiation patterns have been plotted and elevation planes. The simplest reflector antenna consists of two components: a reflecting surface and a much smaller feed antenna, which frequently is located at the reflector‟s focal point. Paraboloidal reflector is entirely defined by the respective parabolic line, i.e., by three basic parameters: the center frequency the diameter and the focal length.

Propagation Characteristics of Circularly and Linearly Polarized Electromagnetic Waves in Urban Macrocell Scenario

Linear polarization (LP) has been the traditional transmission strategy employed in current mobile wireless communication systems. Recently, circular polarization (CP) has regained much interest as CP proves to be a potential candidate to maximize the polarization efficiency component of the link budget. In this paper, the essential concepts of CP are first reinforced by a tutorial description in terms of mathematical insight, propagation characteristics, as well as related applications. Most reported works on CP chiefly focus on the theoretical description of its propagation benefits, such as significant amplitude fade and delay spread (DS) reduction, without simultaneously providing convincing proofs. In other words, CP propagation has not been investigated in sufficient depth. Therefore, we then propose a method for synthesizing CP that is implementation friendly to practical antennas. The engineering validity is subsequently verified by a series of chamber measurements. Intuitively, the polarization trajectory of a synthetical circularly polarized electromagnetic wave is illustrated to further prove the point. Finally, by conducting channel measurement campaigns in a typical urban macrocell scenario, radio propagation characteristics with a dipole as the receive apparatus are analytically extracted for both LP and CP. To facilitate fair competition, the radiation field patterns of two relevant transmitting antennas are intentionally designed to be identical. Numerical results quantitatively demonstrate that, compared with LP, CP can significantly alleviate branch power imbalance between vertical and horizontal polarizations and decrease DS. These advantages are in line with theoretical anticipation and can be fully exploited to upgrade the performance limits of current mobile wireless communication systems.