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Search Results: 1 - 10 of 75037 matches for " Yong-Dan Kong;Qing-Xin Chu "
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Reduction of Numerical Dispersion of the Six-Stages Split-Step Unconditionally-Stable FDTD Method with Controlling Parameters
Yong-Dan Kong;Qing-Xin Chu
PIER , 2012, DOI: 10.2528/PIER11082512
Abstract: A new approach to reduce the numerical dispersion of the six-stages split-step unconditionally-stable finite-difference time-domain (FDTD) method is presented, which is based on the split-step scheme and Crank-Nicolson scheme. Firstly, based on the matrix elements related to spatial derivatives along the x, y, and z coordinate directions, the matrix derived from the classical Maxwell's equations is split into six sub-matrices. Simultaneously, three controlling parameters are introduced to decrease the numerical dispersion error. Accordingly, the time step is divided into six sub-steps. Secondly, the analysis shows that the proposed method is unconditionally stable. Moreover, the dispersion relation of the proposed method is carried out. Thirdly, the processes of determination of the controlling parameters are shown. Furthermore, the dispersion characteristics of the proposed method are also investigated, and the maximum dispersion error of the proposed method can be decreased significantly. Finally, numerical experiments are presented to substantiate the efficiency of the proposed method.
The Adi-FDTD Method Including Lumped Networks Using Piecewise Linear Recursive Convolution Technique
Fen Xia;Qing-Xin Chu;Yong-Dan Kong;Zhi-Yong Kang
PIER M , 2013,
Abstract: The lumped network alternating direction implicit finite difference time domain (LN-ADI-FDTD) technique is proposed as an extension of the conventional ADI-FDTD method in this paper, which allows the lumped networks to be inserted into some ADI-FDTD cells. Based on the piecewise linear recursive convolution (PLRC) technique, the current expression of the loaded place can be obtained. Then, substituting the expression into the ADI-FDTD formulas, the difference equations including an arbitrary linear network are derived. For the sake of showing the validity of the proposed scheme, lumped networks are placed on the microstrip and the voltage across the road is computed by the lumped network finite difference time domain (LN-FDTD) method and LN-ADI-FDTD method, respectively. Moreover, the results are compared with those of obtained by using the circuital simulator ADS. The agreement among all the simulated results is achieved, and the extended ADI-FDTD method has been shown to overcome the Courant-Friedrichs-Lewy (CFL) condition.
High-Order Unconditionally-Stable Four-Step Adi-FDTD Methods and Numerical Analysis
Yong-Dan Kong;Qing-Xin Chu;Rong-Lin Li
PIER , 2013, DOI: 10.2528/PIER12102205
Abstract: High-order unconditionally-stable three-dimensional (3-D) four-step alternating direction implicit finite-difference time-domain (ADI-FDTD) methods are presented. Based on the exponential evolution operator (EEO), the Maxwell's equations in a matrix form can be split into four sub-procedures. Accordingly, the time step is divided into four sub-steps. In addition, high-order central finite-difference operators based on the Taylor central finite-difference method are used to approximate the spatial differential operators first, and then the uniform formulation of the proposed high-order schemes is generalized. Subsequently, the analysis shows that all the proposed high-order methods are unconditionally stable. The generalized form of the dispersion relations of the proposed high-order methods is carried out. Finally, in order to demonstrate the validity of the proposed methods, numerical experiments are presented. Furthermore, the effects of the order of schemes, the propagation angle, the time step, and the mesh size on the dispersion are illustrated through numerical results. Specifically, the normalized numerical phase velocity error (NNPVE) and the maximum NNPVE of the proposed schemes are lower than that of the traditional ADI-FDTD method.
Two Efficient Unconditionally-Stable Four-Stages Split-Step FDTD Methods with Low Numerical Dispersion
Yong-Dan Kong;Qing-Xin Chu;Rong-Lin Li
PIER B , 2013, DOI: 10.2528/PIERB12103011
Abstract: Two efficient unconditionally-stable four-stages split-step (SS) finite-difference time-domain (FDTD) methods based on controlling parameters are presented, which provide low numerical dispersion. Firstly, in the first proposed method, the Maxwell's matrix is split into four sub-matrices. Simultaneously, two controlling parameters are introduced to decrease the numerical dispersion error. Accordingly, the time step is divided into four sub-steps. The second proposed method is obtained by adjusting the sequence of the sub-matrices deduced in the first method. Secondly, the theoretical proofs of the unconditional stability and dispersion relations of the proposed methods are given. Furthermore, the processes of obtaining the controlling parameters for the proposed methods are shown. Thirdly, the dispersion characteristics of the proposed methods are also investigated, and numerical dispersion errors of the proposed methods can be decreased significantly. Finally, to substantiate the efficiency of the proposed methods, numerical experiments are presented.
Study on the Stability and Numerical Error of the Four-Stages Split-Step FDTD Method Including Lumped Inductors
Yong-Dan Kong;Qing-Xin Chu;Rong-Lin Li
PIER B , 2012, DOI: 10.2528/PIERB12062008
Abstract: The stability and numerical error of the extended four-stages split-step finite-difference time-domain (SS4-FDTD) method including lumped inductors are systematically studied. In particular, three different formulations for the lumped inductor are analyzed: the explicit, the semi-implicit, and the implicit schemes. Then, the numerical stability of the extended SS4-FDTD method is analyzed by using the von Neumann method, and the results show that the proposed method is unconditionally-stable in the semi-implicit and the implicit schemes, whereas it is conditionally stable in the explicit scheme, which its stability is related to both the mesh size and the values of the element. Moreover, the analysis of the numerical error of the extended SS4-FDTD is studied, which is based on the Norton equivalent circuit. Theoretical results show that: 1) the numerical impedance is a pure imaginary for the explicit scheme; 2) the numerical equivalent circuit of the lumped inductor is an inductor in parallel with a resistor for the semi-implicit and implicit schemes. Finally, a simple microstrip circuit including a lumped inductor is simulated to demonstrate the validity of the theoretical results.
A Compact Ka-Band Broadband Waveguide-Based Traveling-Wave Spatial Power Combiner with Low Loss Symmetric Coupling Structure
Zhi-Yong Kang;Qing-Xin Chu;Qiong Sen Wu
PIER Letters , 2013, DOI: 10.2528/PIERL12111311
Abstract: A compact Ka-band broadband waveguide-based traveling-wave spatial power combiner is presented. The low loss micro-strip probes are symmetrically inserted into both broadwalls of waveguide, quadrupling the coupling ways but the insertion loss increases little. The measured 16 dB return-loss bandwidth of the eight-way back-to-back structure is from 30 GHz to 39.4 GHz (more than 25%) and the insertion loss is less than 1 dB, which predicts the power-combining efficiency is higher than 90%.
A Novel Approach to the Design of Dual-Band Power Divider with Variable Power Dividing Ratio Based on Coupled-Lines
Zhe Lin;Qing-Xin Chu
PIER , 2010, DOI: 10.2528/PIER10012202
Abstract: This paper presents an approach to the design of a novel dual-band power divider with variable power dividing ratio. To achieve dual-band operation, a novel dual-band quarter-wave length transformer based on coupled-lines is proposed, which is used to replace the quarter-wave length transformer in Wilkinson power divider. The proposed dual-band power divider features a simple compact planar structure with wide bandwidth performance for small frequency ratio. Closed-form design equations with one degree of design freedom are derived using even- and odd-mode analysis and transmission line theory. For verification purpose, power dividers operating at 2.4/3.8 GHz with dividing ratios of 2:1 and 1:1 are designed, simulated and measured. The simulated and measured results are in good agreement.
Lod-Like Method That Characterizes the Analytical Solution
De-An Cao;Qing-Xin Chu
PIER Letters , 2010, DOI: 10.2528/PIERL10050504
Abstract: A LOD-like method that characterizes the analytical solution is proposed to study the one-dimensional (1-D) chiral media. Through theoretical analysis and numerical simulation, it is found that the proposed scheme is unconditionally stable. This scheme employs the new mesh-dividing method for bi-isotropic media, in which the two sections on the right side of the rearranged curl equations are regarded as two directions and the LOD-like algorithm is used to deal with the equivalent two-dimensional (2-D) problem. In the first substep, the conventional LOD method is used in computation, while for the second substep, the analytical solution is employed instead. By simulating the polarization rotation of a mono-frequency linear polarized wave both in a 1-D homogeneous chiral media and through a chiral slab, the scheme is testified to be unconditionally stable.
CPW-FED Square Slot Antenna with Lightening-Shaped Feedline for Broadband Circularly Polarized Radiation
Wen Liao;Qing-Xin Chu
PIER Letters , 2010, DOI: 10.2528/PIERL10080101
Abstract: A new broadband circularly polarized (CP) square slot antenna is evaluated numerically and verified experimentally. The proposed antenna uses a lightening-shaped feedline protruded from the signal line of the feeding coplanar waveguide (CPW). Two symmetrical F-shaped slits embedded in opposite corners of ground plane are designed to obtain an excellent CP bandwidth. By adjusting the dimensions of the lightening-shaped feedline, the CP bandwidth can be further enhanced. Measured results show that the 3-dB axial-ratio bandwidth of the proposed antenna can reach 51.7% (2150 MHz-3650 MHz), and the impedance bandwidth is as large as 60.2% (2150 MHz--4000 MHz) with VSWR ≤ 2. Measured results are in good agreement with the simulation. The proposed antenna can be easily fabricated because of the simple coplanar geometry.
Dual-Band Circularly Polarized Microstrip Antenna with Small Frequency Ratio
Wen Liao;Qing-Xin Chu
PIER Letters , 2010, DOI: 10.2528/PIERL10052101
Abstract: A compact single-feed dual-band circularly polarized (CP) microstrip antenna is evaluated numerically and experimentally. The dual-band performances with small frequency ratio (about 1:1.1) are achieved by a circular patch and a narrow annular-ring, which have small difference in radius. The CP characteristics are achieved by an unequal cross-slot embedded in the circular patch and two orthogonal linear stubs spurred from the annular-ring. The antenna is easy to fabricate. Good agreement is obtained between measured and simulated results.
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