tailieunhanh - Microstrip Antennas Part 19

Tham khảo tài liệu 'microstrip antennas part 19', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | A Practical Guide to 3D Electromagnetic Software Tools 529 Finite or infinite layer structures Although all MoM solvers used an infinite substrate in the simulations FEKO and IE3D are able to model finite substrates. Both finite and infinite substrate models have their advantages and drawbacks. Finite substrate models are supposed to be able to include the effects at the edges. However they enforce the boundary conditions on the top and bottom surfaces of the substrate in a numerical way in this way losing accuracy on these surfaces. Infinite substrate models enforce the boundary condition on the top and bottom surfaces analytically and thus rigorously. However they neglect the edge effects of the finite substrates. A comparison of MoM-based simulation results for both the finite and infinite substrate model is depicted in Fig. 14. The differences are considerable and the conclusion is clear. Accurate modeling of the finiteness of a layer structure is necessary. Since this was not done for the MoM solvers in Fig. 11 this may explain part of the discrepancy. The non-MoM solvers have another issue. They use a box of finite dimensions to contain the structure. However from literature it is well-known that the boundary conditions used on the surface of this box nowadays are of high quality provided that the box is large enough. Fig. 14. Simulation results of GSM antenna for both finite and infinite substrate models. Excitation of the slotline mode in the CPW The topology is clearly not symmetric with respect to the CPW. In particular the signal line of the GSM antenna has a meandered matching line which is short circuited to only one ground plane GP2 in Fig. 5 . This asymmetry may give rise to a radiating slotline mode. In practice the slotline mode is suppressed by connecting the two ground planes of the feeding line with air bridges 64 65 . The ground planes on the test PCB are connected only at the side of the SMA connector. Inevitably the slotline mode