Hologram analysis can also be used to study near field communication nfc antennas. When dealing with the coupling of ss to ls, the near to near field extrapolation technique based on kirchhoffs surface integral representation is used and a sequential transfer method is developed. There are significant cost, size, and complexity details which will lead to a recommendation of one type over the other. Timedomain near to farfield transformation for fdtd in two dimensions article in microwave and optical technology letters 276. According to the time domain calculation sequence in fdtd, the contribution of ss to ls is transferred directly to far zone observation point. Figure 22 far field angle the red region is the near field fresnelkirchhoff diffraction formula. Near and far field calculations in fdtd simulations using kirchhoff surface integral representation omar m. The far field position can be expressed with far field angle the far field. Citeseerx document details isaac councill, lee giles, pradeep teregowda. A universal expression of nearfiledfarfield boundary in stratified structures.
The finite difference time domain fdtd technique models. On the use of the geometric mean in fdtd neartofarfield transformations. Fast fourier transform of the results new algorithms. First, the near surfaces is defined as a set of surfaces capturing all outgoing radiation in the desired directions. This new approach is based directly on the polarization current of the scatterer, not the scattered near fields.
On the use of the geometric mean in fdtd neartofarfield. A new neartofarfield transformation algorithm for threedimensional finitedifferent timedomain is presented in this article. 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. Recently published papers on the near tofar field ntff transformation in the finitedifference timedomain fdtd method have demonstrated accuracy improvements for weakly scattering objects. Osa implementing the near to farfield transformation. For a worst case scenario, results indicate an improvement in the accuracy of the calculated far field responses and radar crosssection rcs in comparison to the original algorithm. 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.
This paper presents a simple and practical method and measurement results of transformation by using the idea. How can i do neartofar field transformation using fdtd. Pier online fdtdtdpo hybrid approach for analysis of. What is the best near field to far field transformation method for. Characterization of the radiation pattern of antennas via. Unlike afdtd, which is designed for radar signature analysis in the far field, nafdtd is an.
A modification to the near field to far field transformation scheme by luebbers et al. A timedomain near to farfield transformation for fdtd in two. Course syllabus elct 863 computational electromagnetics. Simple nearfield to farfield transformation method using. Near field 11 near field vs farfield any antenna can be successfully measured on either a near field or farfield range, with appropriate implementation. Total field scattered field wave generation technique. A timedomain near to farfield transformation for fdtd. Abstract 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. Nafdtd a nearfield finite difference time domain solver. Note that the far field calculation point can be still in the computational volume of fdtd, so you can directly compare the field values from yees algorithm and from nfff transformation for the same point in space. Electromagnetic simulation techniques based on the fdtd. The first technique used to perform the nfff transformation could.
In the present work, a model based on the finite difference time domain fdtd method and the near field to far field nftff transformation for electromagnetic waves propagation is presented. 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. There are three steps involved in this type of calculation. Finally, given that the farfield spectra is derived from the fouriertransformed fields which includes an arbitrary constant factor, we should expect an overall scale and phase difference in the results obtained using the neartofarfield feature with those from a corresponding simulation involving the full computational volume. Pdf on sep 1, 2008, parham mokhtari and others published efficient computation of hrtfs at any distance by fdtd simulation with near to far field transformation find, read and cite all the. This report describes nafdtd, a nearfield finite difference time domain software package developed at the u.
Angora is a free, opensource software package that computes numerical solutions to electromagnetic radiation and scattering problems. Neartofarfield transformations require the tangential electric and magnetic fields over a surface, which we call the integration boundary. 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. With this data, i can display a plane that shows the near e field of my microstrip antenna at z 5mm.
Nearfield and farfield modeling of scattered surface. 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. Timedomain near to farfield transformation for fdtd in. Abstract fdtd based radar cross section rcs and antenna simulations is discussed. Ramahi, member, ieee abstract kirchhoffs surface integral representation ksir is used to calculate the near and far. Osa finitedifference timedomain and nearfieldtofar. Abstract neartofarfield transformations require the tangential electric and magnetic fields over a surface, which we call the integration boundary. Index termsfdtd methods, finite difference methods, finite element methods, nearfield farfield transformation. Where r is the vector from near field to far field.
Near field to far field transformation 18, 19 pouvant prendre en. The transformation of the near field to the corresponding far field is a key step involved in the application of the finitedifference timedomain fdtd technique to the scattering of an electromagnetic wave by a dielectric particle. By using a near to far field transformation, far fields can be determined from the near fields. The template nonfaulty near field of an array is simulated numerically fullwave fdtd solver or fem ansoftansys hfss solver at the same distance an alternative is. Near and farfield calculations in fdtd simulations using. Matlab how to do a near field far field transformation. Does anybody have a 3d2d working code and be so nice to share it. This is also how the performance of nfff is tested in gsvit examples. The boundary condition is applied to a virtual surface, which encloses arbitrarily shaped scatterers. Every modeling technique has strengths and weaknesses, and the fdtd method is. A hybrid technique combining fdtd and series solution for. As we have seen, the fdtd method provides the fields throughout some finite region of space. Time domain nearfield to nearfield transformation using. 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.
Nearfield to farfield transformation for antenna measurements nf2ff. On the otherhand, because of theapproximations appliedto the surface integrals, the standard transformation typically used within the finitedifference timedomain fdtd method 15 is strictly a near to far field transform. In this method, near field data is calculated by fdtd and far field data is also expressed by series solution. A new neartofarfield transformation that combines the fdtd and the series solution is presented. The near tofar field transformation feature is demonstrated using four different examples. The program is designed for quick and efficient programming of fdtd simulations and for extending the available fdtd algorithms with new techniques and features.
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 neartofarfield nfff transformation. When radiation pattern of an antenna or scattering pattern of radar crosssection rcs is measured, its characteristics is usually evaluated in the far field area. Implementing the near to farfield transformation in the. Differential near field holography for small antenna. This report describes nafdtd, a near field finite difference time domain software package developed at the u. 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. This program is based on the finite difference time domain fdtd method and is related to the afdtd software. 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 not practical in applications. It therefore eliminates the numerical errors originating from the spatial offset of the e and h fields, inherent in the standard near tofar field. On the fdtd near tofar field transformations for weakly scattering objects abstract. Near to farfield transformation in the aperiodic fourier. We propose a simple yet effective modification to significantly improve the accuracy of the finitedifference timedomain fdtd near tofar field ntff transformation for calculating the. Pdf finitedifference timedomain and nearfieldtofarfield.
Tutorialneartofar field spectra meep documentation. In general, farfield ranges are a better choice for lower. I honestly dont understand where im doing wrong because im following the books step by step. The first technique used to perform the nfff transformation could only be applied to a single frequency analysis 1, 3. This technique is associated with a threedimensional finitedifference timedomain fdtd model, which solves the maxwell equations in the time domain. 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. Instead, the far zone electromagnetic fields are computed from the near field fdtd data through near field to far field nfff transformation. Pdf modified fdtd neartofarfield transformation for.
Near to far field transformation for a fdtd bor with pml abc. The algorithm implementation in ol es the numerical e aluation of a time integral along the near to far field con ersion. Instead, the farzone electromagnetic fields are computed from the nearfield fdtd data through nearfield to far field nfff. A frequencydomain nearfieldtofarfield transform for planar. I am using the software tool feko to model my patch antenna and to get the near field data.
Capoglu and di zhang, and is currently maintained by di zhang. Near tofar field transformation body of revolution fdtd algorithm for horn antenna design fdtd modeling of highspeed electronic circuits metamaterials and applications moment method mm point matching method, galerkins method, basis functions, weighting functions. Code for scattering from frequencyindependent dielectric materials by john h. Timedomain near to farfield transformation for fdtd.
On the fdtd neartofarfield transformations for weakly. Glisson, fellow, ieee abstractsa near to far eld transformation ntft based on the rwg basis function is proposed for a 2d triangulargrid. Tests with different scenarios show that a computation gain of. I would like to do a near field far field transformation with matlab. It is based on the finitedifference timedomain fdtd method, which is one of the most popular approaches for solving maxwells equations of electrodynamics. 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. While the fdtd technique computes electromagnetic fields within a compact spatial region, scattered andor radiated far fields can be obtained via near tofar field transformations.
A full wave analysis of antenna using 3d fdtd with cpml. We present the study of a spectraldomain near field tofar field nftff transformation, taking into account an interface in the vicinity of a particle. Huygens surface, obtained with the finitedifference timedomain fdtd method. On the otherhand, because of theapproximations appliedto the surface integrals, the standard transformation typically used within the finitedifference time domain fdtd method 15 is strictly a near to farfield transform. Pdf efficient computation of hrtfs at any distance by.
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