scholarly journals High-accuracy quasistatic numerical model for bodies of revolution tailored for RF measurements of dielectric parameters

2021 ◽  
Vol 34 (1) ◽  
pp. 141-156
Author(s):  
Antonije Djordjevic ◽  
Dragan Olcan ◽  
Jovana Petrovic ◽  
Nina Obradovic ◽  
Suzana Filipovic
Keyword(s):  
Numerical Model ◽  
Reflection Coefficient ◽  
Measurement Uncertainty ◽  
Method Of Moments ◽  
High Accuracy ◽  
Frequency Range ◽  
Dielectric Parameters ◽  
Bodies Of Revolution ◽  
Dielectric Bodies ◽  
Rf Measurements

We have developed rotationally symmetrical coaxial chambers for measurements of dielectric parameters of disk-shaped samples, in the frequency range from 1 MHz to several hundred MHz. The reflection coefficient of the chamber is measured and the dielectric parameters are hence extracted utilizing a high-accuracy quasistatic numerical model of the chamber and the sample. We present this model, which is based on the method of-moments solution of a set of integral equations for composite metallic and dielectric bodies. The equations are tailored to bodies of revolution. The model is efficient and accurate so that the major contribution of the measurement uncertainty comes from the measurement hardware.

scholarly journals High-Gain Quad Array of Nonuniform Helical Antennas

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Jelena Lj. Dinkić ◽  
Dragan I. Olćan ◽  
Antonije R. Djordjević ◽  
Alenka G. Zajić
Keyword(s):  
Numerical Model ◽  
Method Of Moments ◽  
Axial Length ◽  
Ground Plane ◽  
High Gain ◽  
Higher Order ◽  
Basis Functions ◽  
Frequency Range ◽  
Helical Antenna ◽  
Helical Antennas

We present a design of a high-gain quad array of nonuniform helical antennas. The design is obtained by optimization of a 3-D numerical model of four nonuniform helical antennas placed above a ground plane, including a model of a feeding network, utilizing the method of moments with higher-order basis functions. The gain of one optimal nonuniform helical antenna can be about 2.5 dB higher than the gain of a uniform helical antenna of the same axial length. Creating a 2×2 array further increases the gain up to about 6 dB. The resulting quad array fits into a box whose dimensions are 2.5×3.3×3.3 wavelengths, and the gain in the main radiating direction is about 20.5 dBi in the frequency range from 0.9 GHz to 1.1 GHz. The design is verified by measurements of a prototype of the quad array.

scholarly journals An Improved Time Integration Method Based on Galerkin Weak Form with Controllable Numerical Dissipation

2021 ◽  
Vol 11 (4) ◽  
pp. 1932
Author(s):  
Weixuan Wang ◽  
Qinyan Xing ◽  
Qinghao Yang
Keyword(s):  
High Frequency ◽  
Integration Method ◽  
Time Integration ◽  
Low Frequency ◽  
Weak Form ◽  
High Accuracy ◽  
Numerical Dissipation ◽  
Frequency Range ◽  
Time Integration Method ◽  
Numerical Damping

Based on the newly proposed generalized Galerkin weak form (GGW) method, a two-step time integration method with controllable numerical dissipation is presented. In the first sub-step, the GGW method is used, and in the second sub-step, a new parameter is introduced by using the idea of a trapezoidal integral. According to the numerical analysis, it can be concluded that this method is unconditionally stable and its numerical damping is controllable with the change in introduced parameters. Compared with the GGW method, this two-step scheme avoids the fast numerical dissipation in a low-frequency range. To highlight the performance of the proposed method, some numerical problems are presented and illustrated which show that this method possesses superior accuracy, stability and efficiency compared with conventional trapezoidal rule, the Wilson method, and the Bathe method. High accuracy in a low-frequency range and controllable numerical dissipation in a high-frequency range are both the merits of the method.

scholarly journals Broadband Adaptive RCS Computation through Characteristic Basis Function Method

2014 ◽  
Vol 2014 ◽  
pp. 1-5
Author(s):  
Guohua Wang ◽  
Yufa Sun
Keyword(s):  
Cross Section ◽  
Basis Function ◽  
Function Method ◽  
High Accuracy ◽  
Wide Frequency Range ◽  
Singular Value ◽  
Basis Functions ◽  
Frequency Range ◽  
Arbitrary Frequency ◽  
Value Decomposition

A broadband radar cross section (RCS) calculation approach is proposed based on the characteristic basis function method (CBFM). In the proposed approach, the desired arbitrary frequency band is adaptively divided into multiple subband in consideration of the characteristic basis functions (CBFs) number, which can reduce the universal characteristic basis functions (UCBFs) numbers after singular value decomposition (SVD) procedure at lower subfrequency band. Then, the desired RCS data can be obtained by splicing the RCS data in each subfrequency band. Numerical results demonstrate that the proposed method achieve a high accuracy and efficiency over a wide frequency range.

scholarly journals Studying of dielectric spectra of YCu0.15Mn0.85O3 solid solution with the use of complex conductivity

2021 ◽  
pp. 2160013
Author(s):  
A. V. Nazarenko ◽  
A. V. Pavlenko ◽  
Y. I. Yurasov
Keyword(s):  
Solid Solution ◽  
Electrical Conductivity ◽  
Model Description ◽  
Complex Conductivity ◽  
Electrophysical Properties ◽  
Approximation Model ◽  
Frequency Range ◽  
Dielectric Parameters ◽  
Frequency Behavior ◽  
Complex Electrical Conductivity

This work presents the results of studying the electrophysical properties of the YCu[Formula: see text]Mn[Formula: see text]O3 solid solution in the range of temperatures of [Formula: see text] = 26–400[Formula: see text]C and frequency range of [Formula: see text] = 102–105 Hz. A model description of the revealed dispersion of dielectric parameters in the material is made. The nonclassical modified Havriliak–Negami model written for complex electrical conductivity was used as an approximation model. It is shown that the application of this model almost exactly describes the frequency behavior of the dielectric constant [Formula: see text]/[Formula: see text], the dielectric loss tangent tg[Formula: see text] as well as the real and imaginary parts of complex conductivity [Formula: see text] and [Formula: see text]. The results of this work are an important step in identifying the opportunities and understanding the applications of this model.

scholarly journals NUMERICAL MODEL OF BREAKWATER WAVE FLOWS

1988 ◽  
Vol 1 (21) ◽  
pp. 149 ◽  
Author(s):  
Alex C. Thompson
Keyword(s):  
Mathematical Model ◽  
Numerical Model ◽  
Reflection Coefficient ◽  
Water Wave ◽  
Wave Equations ◽  
Seepage Flow ◽  
Experimental Results ◽  
Simplified Model ◽  
Flow Equations ◽  
Shallow Water Wave Equations

A mathematical model of flow on a sloping breakwater face is described and results of calculations compared with some experimental results to show how the model can be calibrated. Flow above the surface of the slope is represented by the shallow water wave equations solved by a finite difference method. Flow within the breakwater is calculated by one of two methods. A solution of the linear seepage flow equations, again using finite differences or a simplified model of inflow can be used. Experimental results for runup and reflection coefficient are from tests performed at HRL Wallingford.

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