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Wave Propagation Part 11

Tham khảo tài liệu 'wave propagation part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 342 Wave Propagation This method does not use time-domain discretization unlike the FDTD method. In the case of the FDTD method time evolution of propagating waves in media is converted into frequency spectra. To deal with the wide frequency range simultaneously it is required to perform auxiliary calculation to reinforce the dispersive dependence of the permittivity such as shown in equation 2.2.2 and such a scheme is referred to as frequency-dependent FDTD method which is shown in Section 3.1.3. In our method used here a monochromatic wave at one frequency is assumed in each calculation step with a corresponding and precise value of the permittivity from equation 2.1.2 . In other words the frequency step which we set for searching wave propagation is crucial to assure the entire calculation accuracy. A narrower frequency step will yield a more accurate determination of a propagating wave although more CPU time is required. Using this scheme we calculated band diagrams with 1 m co that is a collisionless case as shown in Figs. 5-9. when 1 m is introduced as a finite value comparable to co and ffi pe note that the resonance-like frequency is searched on the complex frequency for a real wave number like in the cases of the plane-wave expansion method described in Section 3.1.1. If we consider spatial wave damping of the static propagation in a finite region a complex wave number is derived for a real value of frequency. This method enables US to take such a flexible approach. The relation of complex wavenumber and complex wave frequency was well investigated by Lee et al. Lee Mok 2010 . 5 10 15 20 25 X mm Fig. 4. 2D Wave propagation along a chain structure composed of columnar plasams at 6.2 GHz. Inset figures shows assumed configuration with assumed . profile in shape of Oth order Bessel function with peak density of 1.5 X1013 cm-3. 3.1.3 Finite-difference time domain method for dispersive media In Section 3.1.2 we mentioned a different numerical method which saves