Unlike afdtd, which is designed for radar signature analysis in the far field, nafdtd is an. Capoglu and di zhang, and is currently maintained by di zhang. There are three steps involved in this type of calculation. Spherical nearfield analysis software allows the far field results to be presented in a variety of spherical coordinate systems and polarization bases. One is directly obtaining scattered far field by adopting strattonchu integral formula. Angora is a free, opensource software package that computes numerical solutions to electromagnetic radiation and scattering problems. On the fdtd neartofarfield transformations for weakly. This technique is associated with a threedimensional finitedifference timedomain fdtd model, which solves the maxwell equations in the time domain. Computations on arbitrary surfaces in fdtd space citeseerx. Focused on the methods of near zone to far zone field transformation in solving scattering problem by fdtd method, two new approaches are presented. With the fdtd technique, the direct evaluation of the far field calls for an excessively large computational domain, which is not practical in applications. Second, we run the simulation using a pulsed source or alternatively, a cw source via the frequency. If the geometry of the surrounding enviroment of the antenna is complicated, its better to go directly to the numerical approach like mom.
First, we need to define the near surfaces as a set of surfaces capturing all outgoing radiation in the desired directions. Instead, the far zone electromagnetic fields are computed from the near field fdtd data through near field to far field nfff transformation technique 5. The main fdtd volume is left as is in the classical fdtd method, but the task of the near to far field transformation ntfft module is distributed. The near field is governed by multipole type fields, which can be considered as collections of dipoles with a fixed phase relationship. A full wave analysis of antenna using 3d fdtd with cpml. Neartofarfield transformations require the tangential electric and magnetic fields over a surface, which we call the integration boundary. Hello everyone, i want to do near to far field transformation by using fdtd how. A new neartofarfield transformation algorithm for threedimensional finitedifferent timedomain is presented in this article. The first technique used to perform the nfff transformation could only be applied to a. Neartofarfield transformation in fdtd for high resolution radar. Optifdtd uses equation 72 to calculate the narrow angle far field transform. The simulation script is in examplesantennaradiation. Near to far field transformation algorithm with the fdtd technique, the direct evaluation of the far field calls for an excessively large computational domain, which is. It therefore eliminates the numerical errors originating from the.
We often need an information about radiation properties in the far field, which for most of the cases is the domain where we are able to measure something. The first technique used to perform the nfff transformation could only be applied to a single frequency analysis 1, 3. Nearfield to nearfarfield transformation for arbitrary nearfield geometry utilizing an equivalent electric current and mom tapan kumar sarkar, fellow, ieee, and ardalan taaghol abstract presented here is a method for computing near and far. The function ehfields can calculate the e and h fields at any point in space near or far. Geometry associated with the neartofarfield transformation in 2d. The program goes above and beyond characterizing the far field pattern, as it actually takes the user through a stepbystep processing of data and plotting from start to finish. Moreover, material properties are considered with the use of dispersion models. Spontaneousemission rate and lightextraction efficiency of organic lightemitting diodes oleds topics to be covered.
A new 3d simulation method for the construction of optical. Description the howland companys spherical n2f software is a standalone package that transforms the spherical nearfield radiation pattern of an antenna to the farfield radiation pattern that the data would produce at an infinite. In this region, it is dominated by electric or magnetic fields with electric dipole characteristics. Fdtd figure 22 farfield angle the red region is the near field.
Total field scattered field wave generation technique. Taflove and umashankar developed the first fdtd electromagnetic wave scattering models computing sinusoidal steadystate nearfields, farfields, and radar crosssection for two and threedimensional structures. This can be done using a near field to far field nfff transformation, which uses the values at some set of planes enclosing all the sources and scatterers and calculates the far field time domain or frequency domain results from it for a certain location of far field. Jan 15, 2014 nf2ff is a great and clear resource for understanding the near field to far field transformation process. Tests with different scenarios show that a computation gain of. Figure 22 farfield angle the red region is the near field fresnelkirchhoff diffraction formula. It therefore eliminates the numerical errors originating from the spatial offset of the e and h fields, inherent in the standard near tofar field. Focused on the methods of nearzone to farzone field transformation in solving scattering problem by fdtd method, two new approaches are presented. The near to far field transformation feature is demonstrated using four different examples. The improvements are achieved by modifications of the standard ntff transformation which is based on interpolation of the spatially shifted fields in the fdtd grid. Where r is the vector from near field to far field. On the use of the geometric mean in fdtd near tofar field transformations dirk j. This is usefull for computing surrounding field in an area near an antenna, in the transition zone between near and far field. For conversion between far and near field there are a lot of papers, one of the oldest and simplest, as far as i know is brown, j.
A near zone to far zone transformation process utilizing a formulated eigenfunction expansion of spheroidal waveharmonics gerald f. Osa implementing the near to farfield transformation. The primary objective of the nf2ff sourceforge project is to provide the phased array community with an opensource matlab alternative to proprietary nf measurement software. Near field far field transformation matlab answers. The far field position can be expressed with far field angle the far field distance zd. Tutorialneartofar field spectra meep documentation. This is the surface of the neartofar field transformation, called in brief ntf box, whereat the tangential near fields directly produced by the fdtd simulation are. Farfield diffraction spectra of metasurfaces topics to be covered. Finitedifference timedomain fdtd simulation results demonstrate that. Citeseerx document details isaac councill, lee giles, pradeep teregowda.
Its features include simulation in 1d, 2d, and 3d cartesian coordinates, distributed memory parallelism on any system supporting the mpi standard, portable to any unixlike system, variuos dispersive. A free electromagnetic solver for farfield and near. Tutorialneartofar field spectra meep documentation read. This program is based on the finite difference time domain fdtd method and is related to the afdtd software. Finitedifference timedomain or yees method named after the chinese american applied mathematician kane s. We present the study of a spectraldomain near field tofar field nftff transformation, taking into account an interface in the vicinity of a particle. Instead, the far zone electromagnetic fields are computed from the near field fdtd data through a near field to far field nfff transformation technique.
This paper proposes an algorithm based on the equi alence principle to calculate, straightforwardly in the time domain, the transient far field response of a twodimensional structure. Introduction nearfieldtofarfield transforms nfffts involve the formulation of the radiated far. Code issues 95 pull requests 10 actions projects 0 security insights. For radiation pattern calculation the socalled huygens surface is required. The adaption makes no changes to the calculations but replaces the complex data set with text based input files. What is the best near field to far field transformation. Ab angora is a free, opensource software package implementing the finitedifference timedomain fdtd method.
Nf sites allow for hologram analysis, low sidelobes characterization, and do not require a rotating pedestal capable of bearing the weight of the phased array. This paper presents a simple and practical method and measurement results of transformation by using the idea of arrayfactor for direct far field prediction from the near field data of antenna and rcs in cylindrical scanning system. It is based on the finitedifference timedomain fdtd method, which is one of the most popular approaches for solving maxwells equations of electrodynamics. How can i do neartofar field transformation using fdtd. Near and farfield calculations in fdtd simulations using. Nearfield to farfield transformation chris view profile this is an adaption of the awesome nf2ff script to give the far field characteristics of an antenna from the nearfield data set. Standard fdtd yee cell showing the surfaces used for calculating the e and h. Electromagnetic simulation techniques based on the fdtd. Far field diffraction spectra of metasurfaces topics to be covered. Gmes is a free finitedifference timedomain fdtd simulation python package developed at gist to model photonic devices. Farfield and nearfield radiative heat transfer in layered periodic structures.
The far field is the region in which the field acts as normal electromagnetic radiation. Diagram showing how the terms constituting the surface integral contribute to e x x. The far field transformations figure 3 use the fdtd calculated near fields right behind the cell and return the three complex components of the electromagnetic fields at 1 meter distance i. The near tofar field transformation feature is demonstrated using four different examples. Near and far field calculations in fdtd simulations 755 fig. Nearfield to nearfarfield transformation for arbitrary. Second, the simulation is run using a pulsed source or alternatively, a cw source via the frequencydomain solver to. Li et al modified fdtd near tofar field transformation for improved backscattering calculation 37 fig. Optimized for nanoscale optics scanning near field optical microscopy, rough surface scattering and solar cells. Nafdtd a nearfield finite difference time domain solver. First, the near surfaces is defined as a set of surfaces capturing all outgoing radiation in the desired directions.
Figure 22 far field angle the red region is the near field fresnelkirchhoff diffraction formula. Compared to conventional near tofar field transformation techniques, the proposal allows one to easily evaluate the guidedmode radiation diagrams, even if material dissipation is present in the stack, and thus to simultaneously track the coupling of light to all channels i. Not available on the use of the geometric mean in fdtd near tofar field transformations. The capability to do near to far field transformation does not currently exist in antenna toolbox. Field output in the hdf5 standard scientific data format, supported by many visualization tools. The program goes above and beyond characterizing the farfield pattern, as it actually takes the user through a stepbystep processing of. We demonstrate meeps near to far field transformation feature using four different examples. Near to farfield transform package combining efficient processing, proven nist algorithms, and an intuitive gui. With this data, i can display a plane that shows the near e field of my microstrip antenna at z 5mm. Wide angle far field transform is based on the fresnelkirchhoff diffraction formula 1. Ricciardi abstract in the field of antenna design and analysis, often the need arises to numerically extrapolate the far zone performance of a radiating structure from its known or assumed. These include treatment of planar stratified and random materials, the creation of current sources and incident beams, nearfieldtofarfield transformation, optical imaging and nanooptics, and the recording of fields. When the finitedifference timedomain fdtd method is applied to lightscattering computations, the far fields can be obtained by means of integrating the near fields either over the volume bounded by the particles surface or on a regular surface encompassing the scatterer.
With the traditional fdtd method, the huygens surface is set. Nf2ff is a great and clear resource for understanding the nearfield to farfield transformation process. Neartofarfield transformation in fdtd for high resolution radar signal simulation. These include treatment of planar stratified and random materials, the creation of current sources and incident beams, near field tofar field transformation, optical imaging and nanooptics, and the recording of fields. Timedomain near to farfield transformation for fdtd in. The exact method of near field to far field transformation has been reported from 1970s for antenna14 and rcs measurement5,6. The book begins with two chapters that introduce the basic concepts of the 3d cartesian fdtd method, followed by discussions of advanced fdtd methods such as conformal techniques, dispersive media, circuit elements, and near to far field transformation. A more practical method for transforming field values to the far zone and for calculations of radiation gain or radar scattering patterns is to use a transformation to convert the near zone values in the fdtd grid into a far field value at some location away from the grid. The algorithm implementation in ol es the numerical e aluation of a time integral along the near to far field. Fast fourier transform of the results new algorithms.
Characterization of the radiation pattern of antennas via. Huygens surface, obtained with the finitedifference timedomain fdtd method. Radiation and scattering qwed software for electromagnetic. Hello everyone, im trying to implement near to far field transformation frequency domain for my fdtd code in matlab following tafloves books but it doesnt work. Fourier modal method rigorous coupled wave analysis and the scattering matrix method. Filho, lua an extensible extension language, software. A timedomain near to farfield transformation for fdtd. Thus a near field measurement method can be applied to predict the antenna or radar crosssection rcs pattern which cannot be physically measured from far distance. Neartofarfield transformation the remaining integral on the left side of 14. Recently published papers on the near tofar field ntff transformation in the finitedifference timedomain fdtd method have demonstrated accuracy improvements for weakly scattering objects. Fdtd is very efficient when making near field calculations, while for the far field it is necessary to use an additional method to perform a near tofar field nfff transformation.
Does anybody have a 3d2d working code and be so nice to share it. Nearfield optical microscopy simulations using graphics processing units, surf. Nearfield to farfield transformation file exchange. Osa finitedifference timedomain and nearfieldtofar. Near field nf ranges offer a convenient alternative to compact antenna test ranges catr and anechoic far field ranges for the measurement of phased arrays 1,2,3,4,5,6,7,8,9.
We demonstrate meeps near tofar field transformation feature using four different examples. However, the staggered nature of the finitedifference timedomain grid is problematic in that the electric and magnetic fields are not collocated in either space or time. A timedomain near to farfield transformation for fdtd in two. When radiation pattern of an antenna or scattering pattern of radar crosssection rcs is measured, its characteristics is usually evaluated in the far field. This paper presents a simple and practical method and measurement results of transformation by using the idea. For light scattering by a sphere, the accurate near field components on the fdtd staggered. I am using the software tool feko to model my patch antenna and to get the near field data. Jun 11, 2010 this is an adaption of the awesome nf2ff script to give the far field characteristics of an antenna from the near field data set. Simple nearfield to farfield transformation method using. A full wave analysis of antenna using 3d fdtd with cpml and. With this data, i can display a plane that shows the near efield of my microstrip antenna at z 5mm. Yee, born 1934 is a numerical analysis technique used for modeling computational electrodynamics finding approximate solutions to the associated system of differential equations. The main fdtd volume is left as is in the classical fdtd method, but the task of the near tofar field transformation ntfft module is distributed. Matlab how to do a near field far field transformation.
On the use of the geometric mean in fdtd neartofarfield. The code features planar near field to far field transforms with rectangular waveguide probe correction. Simple near field to far field transformation method using antenna arrayfactor hirokazu kobayashi, yoshio yamaguchi, yi cui department of information engineering, niigata university, niigata, 2118121, japan. Near and farfield calculations in fdtd simulations 755 fig. Abstract fdtd based radar cross section rcs and antenna simulations is discussed.
This is the surface of the neartofar field transformation, called in brief ntf box, whereat the tangential near fields directly produced by the fdtd simulation are transformed into the far field radiation patterns using greens function. A timedomain near to farfield transformation for fdtd in. I would like to do a near field far field transformation with matlab. Correction for the pattern, input characteristics, and gain of the probe used in the measurement is supported by this transformation software. Field analyses including flux spectra, maxwell stress tensor, frequency extraction, local density of states and energy integrals, near to far field transformations. The neartofar field transformation feature is demonstrated using four different examples. However, as fdtd is an universal method, it can be used for any other purposes. Nearfield to farfield transform software the howland company. Main mission of this project is to convert set of already developed software tools described here. This report describes nafdtd, a nearfield finite difference time domain software package developed at the u. This new approach is based directly on the polarization current of the scatterer, not the scattered near fields. The book begins with two chapters that introduce the basic concepts of the 3d cartesian fdtd method, followed by discussions of advanced fdtd methods such as conformal techniques, dispersive media, circuit elements, and near tofar field transformation.
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