Tham khảo tài liệu 'microstrip antennas part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 290 Microstrip Antennas scheme and Courant s maximum stable time-step FIT results in the same set of equations as the Finite-Difference Time-Domain FDTD technique Gustrau Manteuffel 2006 . The TS calculates the broadband behaviour of electromagnetic EM devices in a single simulation run with an arbitrarily fine frequency resolution thus without missing any resonance peaks Vasylchenko et al. 2007a . Time-domain solvers are particularly suitable for designing wideband antennas and passive microwave systems such as waveguide components filters couplers and connectors. For active microwave design co-simulation is required between the EM solver and a non-linear circuit simulator such as Agilent Advanced Design System or APLAC . TSs like CST MWS can easily handle exotic materials such as frequency-dependent dispersive and ferri ferro-magnetic materials. The ability to naturally include such difficult materials in models is one of the main strengths of TSs over FEM- and MoM-based solvers although the two latter have recently improved their material-handling capabilities Vasylchenko et al. 2007b . A spatially non-uniform adaptive hexahedral mesh discretized the objects and the solvable space in between. The mesh was refined four-fold near the edges of Perfect Electric Conductor PEC objects and inside the substrate to capture the large gradients of the E-field. Tetrahedral meshing is possible through Floquet modes only when FIT is applied in the frequency domain in which case the technique results in the Finite Element Method FEM . Nevertheless the FIT engine used here employs the Perfect Boundary Approximation PBA technique Munteanu et al. 2010 Weiland et al. 2008 and therefore the hexahedral mesh did not result in any object staircasing whatsoever. A wideband Gaussian pulse excited the structures its spectral content ranged from DC to GHz. The simulator stopped when the initial system energy decayed by 50 dB. This was a good trade-off between simulation speed and .
