Since the time step of the traditional finite-difference time-domain(FDTD) method is limited by the small grid size, it is inefficient when dealing with the electromagnetic problems of multi-scale structures.Therefore...Since the time step of the traditional finite-difference time-domain(FDTD) method is limited by the small grid size, it is inefficient when dealing with the electromagnetic problems of multi-scale structures.Therefore, the explicit and unconditionally stable FDTD(US-FDTD) approach has been developed to break through the limitation of Courant–Friedrich–Levy(CFL) condition.However, the eigenvalues and eigenvectors of the system matrix must be calculated before the time iteration in the explicit US-FDTD.Moreover, the eigenvalue decomposition is also time consuming, especially for complex electromagnetic problems in practical application.In addition, compared with the traditional FDTD method, the explicit US-FDTD method is more difficult to introduce the absorbing boundary and plane wave.To solve the drawbacks of the traditional FDTD and the explicit US-FDTD, a new hybrid FDTD algorithm is proposed in this paper.This combines the explicit US-FDTD with the traditional FDTD, which not only overcomes the limitation of CFL condition but also reduces the system matrix dimension, and introduces the plane wave and the perfectly matched layer(PML) absorption boundary conveniently.With the hybrid algorithm, the calculation of the eigenvalues is only required in the fine mesh region and adjacent coarse mesh region.Therefore, the calculation efficiency is greatly enhanced.Furthermore, the plane wave and the absorption boundary introduction of the traditional FDTD method can be directly utilized.Numerical results demonstrate the effectiveness, accuracy, stability, and convenience of this hybrid algorithm.展开更多
对已有的Z变换时域有限差分法(Z-transformation Finite Difference Time Domain,Z-FDTD)在电磁波与非均匀磁化等离子体中的传输特性分析的计算误差问题进行了研究,并探讨了一种修正计算误差的Z变换时域有限差分方法(Modified Z-transfo...对已有的Z变换时域有限差分法(Z-transformation Finite Difference Time Domain,Z-FDTD)在电磁波与非均匀磁化等离子体中的传输特性分析的计算误差问题进行了研究,并探讨了一种修正计算误差的Z变换时域有限差分方法(Modified Z-transform Finite Difference Time Domain,MZ-FDTD),以提升Z-FDTD方法对非均匀磁化等离子体的适用性。对MZ-FDTD和Z-FDTD之间的计算误差问题,通过严格的公式推导求得该误差的计算公式,并引入误差分析因子,对比分析了该误差受空间步长和非均匀磁化等离子体的物理特性的影响特征,在充分的误差分析与网格参数对比后,以电磁波在非均匀磁化等离子体中的传输特性为分析目标,举例说明了MZ-FDTD的优越性。研究结果表明,相比于经典Z-FDTD,通过MZ-FDTD方法计算得到的数值结果具有更高的计算准确度,较低的运行时间和较少的运行内存占用。此外,对电磁波在非均匀等离子体中传输特性分析的举例说明也证明了相比于Z-FDTD,优化的Z-FDTD方法无论是在较低频段还是较高频段都保持较好的稳定性。在今后的工作中,使用MZ-FDTD方法研究非均匀磁化等离子体问题将会获得更好的计算结果,这项工作中的误差分析方法也将对某些计算电磁学在等离子体中的应用与优化工作起到一定的帮助作用。展开更多
The micro-genetic algorithm (MGA) optimization combined with the finite-difference time-domain (FDTD) method is applied to design a band-notched ultra wide-band (UWB) antenna. A U-type slot on a stepped U-type UWB mon...The micro-genetic algorithm (MGA) optimization combined with the finite-difference time-domain (FDTD) method is applied to design a band-notched ultra wide-band (UWB) antenna. A U-type slot on a stepped U-type UWB monopole is used to obtain the band-notched characteristic for 5 GHz wireless local area network (WLAN) band. The measured results show that voltage standing wave ration (VSWR) less than 2 covers 3.1-10.6 GHz operating band and VSWR more than 2 is within 5.150-5.825 GHz notched one with the highest value of 5.6. Agreement among the calculated, HFSS simulated and measured results validates the effiectiveness of this MGA-FDTD method, which is efficient for UWB antennas design.展开更多
High Q inductors are the important elements for RF circuit design. In this paper, the FDTD method is applied to explain the crowding effect of the spiral inductor , which can never be accurately analyzed by analytical...High Q inductors are the important elements for RF circuit design. In this paper, the FDTD method is applied to explain the crowding effect of the spiral inductor , which can never be accurately analyzed by analytical solutions. The experimental results verify the FDTD simulation. The micro genetic algorithms and FDTD are combined to design the high Q of the inductor, the results show the efficiency of this exploration.展开更多
A new method to reduce the numerical dispersion of the three-dimensional Alternating Di-rection Implicit Finite-Difference Time-Domain (3-D ADI-FDTD) method is proposed. Firstly,the numerical formulations of the 3-D A...A new method to reduce the numerical dispersion of the three-dimensional Alternating Di-rection Implicit Finite-Difference Time-Domain (3-D ADI-FDTD) method is proposed. Firstly,the numerical formulations of the 3-D ADI-FDTD method are modified with the artificial anisotropy,and the new numerical dispersion relation is derived. Secondly,the relative permittivity tensor of the artificial anisotropy can be obtained by the Adaptive Genetic Algorithm (AGA). In order to demon-strate the accuracy and efficiency of this new method,a monopole antenna is simulated as an exam-ple. And the numerical results and the computational requirements of the proposed method are com-pared with those of the conventional ADI-FDTD method and the measured data. In addition the re-duction of the numerical dispersion is investigated as the objective function of the AGA. It is found that this new method is accurate and efficient by choosing proper objective function.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.61571348)the Equipment Pre-Research Foundation of China(Grant No.61405180202)
文摘Since the time step of the traditional finite-difference time-domain(FDTD) method is limited by the small grid size, it is inefficient when dealing with the electromagnetic problems of multi-scale structures.Therefore, the explicit and unconditionally stable FDTD(US-FDTD) approach has been developed to break through the limitation of Courant–Friedrich–Levy(CFL) condition.However, the eigenvalues and eigenvectors of the system matrix must be calculated before the time iteration in the explicit US-FDTD.Moreover, the eigenvalue decomposition is also time consuming, especially for complex electromagnetic problems in practical application.In addition, compared with the traditional FDTD method, the explicit US-FDTD method is more difficult to introduce the absorbing boundary and plane wave.To solve the drawbacks of the traditional FDTD and the explicit US-FDTD, a new hybrid FDTD algorithm is proposed in this paper.This combines the explicit US-FDTD with the traditional FDTD, which not only overcomes the limitation of CFL condition but also reduces the system matrix dimension, and introduces the plane wave and the perfectly matched layer(PML) absorption boundary conveniently.With the hybrid algorithm, the calculation of the eigenvalues is only required in the fine mesh region and adjacent coarse mesh region.Therefore, the calculation efficiency is greatly enhanced.Furthermore, the plane wave and the absorption boundary introduction of the traditional FDTD method can be directly utilized.Numerical results demonstrate the effectiveness, accuracy, stability, and convenience of this hybrid algorithm.
文摘对已有的Z变换时域有限差分法(Z-transformation Finite Difference Time Domain,Z-FDTD)在电磁波与非均匀磁化等离子体中的传输特性分析的计算误差问题进行了研究,并探讨了一种修正计算误差的Z变换时域有限差分方法(Modified Z-transform Finite Difference Time Domain,MZ-FDTD),以提升Z-FDTD方法对非均匀磁化等离子体的适用性。对MZ-FDTD和Z-FDTD之间的计算误差问题,通过严格的公式推导求得该误差的计算公式,并引入误差分析因子,对比分析了该误差受空间步长和非均匀磁化等离子体的物理特性的影响特征,在充分的误差分析与网格参数对比后,以电磁波在非均匀磁化等离子体中的传输特性为分析目标,举例说明了MZ-FDTD的优越性。研究结果表明,相比于经典Z-FDTD,通过MZ-FDTD方法计算得到的数值结果具有更高的计算准确度,较低的运行时间和较少的运行内存占用。此外,对电磁波在非均匀等离子体中传输特性分析的举例说明也证明了相比于Z-FDTD,优化的Z-FDTD方法无论是在较低频段还是较高频段都保持较好的稳定性。在今后的工作中,使用MZ-FDTD方法研究非均匀磁化等离子体问题将会获得更好的计算结果,这项工作中的误差分析方法也将对某些计算电磁学在等离子体中的应用与优化工作起到一定的帮助作用。
基金supported by the Shanghai Leading Academic Discipline Project (Grant No.S30108)
文摘The micro-genetic algorithm (MGA) optimization combined with the finite-difference time-domain (FDTD) method is applied to design a band-notched ultra wide-band (UWB) antenna. A U-type slot on a stepped U-type UWB monopole is used to obtain the band-notched characteristic for 5 GHz wireless local area network (WLAN) band. The measured results show that voltage standing wave ration (VSWR) less than 2 covers 3.1-10.6 GHz operating band and VSWR more than 2 is within 5.150-5.825 GHz notched one with the highest value of 5.6. Agreement among the calculated, HFSS simulated and measured results validates the effiectiveness of this MGA-FDTD method, which is efficient for UWB antennas design.
文摘High Q inductors are the important elements for RF circuit design. In this paper, the FDTD method is applied to explain the crowding effect of the spiral inductor , which can never be accurately analyzed by analytical solutions. The experimental results verify the FDTD simulation. The micro genetic algorithms and FDTD are combined to design the high Q of the inductor, the results show the efficiency of this exploration.
基金the National Natural Science Foundation of China (No. 60271012)Research Foundation of ZTE Corporation.
文摘A new method to reduce the numerical dispersion of the three-dimensional Alternating Di-rection Implicit Finite-Difference Time-Domain (3-D ADI-FDTD) method is proposed. Firstly,the numerical formulations of the 3-D ADI-FDTD method are modified with the artificial anisotropy,and the new numerical dispersion relation is derived. Secondly,the relative permittivity tensor of the artificial anisotropy can be obtained by the Adaptive Genetic Algorithm (AGA). In order to demon-strate the accuracy and efficiency of this new method,a monopole antenna is simulated as an exam-ple. And the numerical results and the computational requirements of the proposed method are com-pared with those of the conventional ADI-FDTD method and the measured data. In addition the re-duction of the numerical dispersion is investigated as the objective function of the AGA. It is found that this new method is accurate and efficient by choosing proper objective function.
