The charges,currents and near‐field characteristics of the transparent source for the FDTD method |
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Authors: | Ching‐Lieh Li Shao‐Hon Chen Chien‐Wei Liu Chih‐Wei Lin |
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Affiliation: | 1. Department of Electrical Engineering , Tamkang University , Taipei, Taiwan 251, R.O.C. Phone: 886–2–26215656 ext. 2735 Fax: 886–2–26215656 ext. 2735 E-mail: li@ee.tku.edu.tw);2. Department of Electrical Engineering , Tamkang University , Taipei, Taiwan 251, R.O.C. |
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Abstract: | Abstract The electromagnetic characteristics of a transparent source for the finite‐difference time‐domain (FDTD) method are investigated. The approximate formulations for the corresponding electric and magnetic fields at the source are first reported, while the associated charges and current are also demonstrated. The approximate E field and H field are very closely related to the FDTD simulated results. It is shown that the magnetic field is proportional to the temporal derivative of the electric field at the source node, while the electric field is proportional to the temporal integration of the driving function. Static charges may be built up to produce static E fields after the driving function has passed, which are responsible for the dc offset problem in the pulsed FDTD algorithm. The dc offset is verified for the case of Gaussian pulse excitation and is avoided via the use of a bipolar pulse. |
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Keywords: | FDTD transparent source dc offset |
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