volume | PIER Journals

Abstract

An FDTD methodology is provided herein that allows for TEM excitation and detection of signals associated with N-port network analysis. The scheme is based upon the numerical solution of Laplace's equation in the context of the standard Yee grid. The invocation of both equivalence and orthogonality of modes principles assures that the TEM mode of interest is both exclusively excited and detected. Electric and magnetic surface currents are employed to render zero backward radiation from the source plane. Orthogonality is utilized at the terminal plane to extract the TEM mode from a multi-mode signal, provided that the spectrum of the guiding structure is discrete. The advantage of this approach is found in the placement of both the terminal and source planes — both can be placed as close to each other and to the network as necessary, thus alleviating the computational and memory burdens of the simulation. Examples pertaining to this methodology include stripline structures and the monopole strip antenna. The microstrip patch antenna is also considered to demonstrate the difficulties associated with the excitation and detection of quasi-TEM signals in the midst of radiation terms.

1. Collin, R. G., Field Theory of Guided Waves, 2nd edition, 1991.

2. Sheen, D. M., S. M. Ali, M. D. Abouzahra, and J. A. Kong, "Application of the three-dimensional finite-difference time-domain method to the analysis of planar microwave circuits," IEEE Trans. Microwave Theory Tech., Vol. 38, No. 7, 849-856, 1990.
doi:10.1109/22.55775

3. Luebbers, R. J. and H. S. Langdon, "A simple feed model that reduces time steps needed for FDTD antenna and microstrip calculations," IEEE Trans. Ant. Propagat., Vol. 44, No. 7, 1000-1005, 1996.
doi:10.1109/8.504308

4. Buechler, D. N., D. H. Roper, C. H. Durney, and D. A. Christensen, "Modeling sources in the FDTD formulation and their use in quantifying source and boundary condition errors," IEEE Trans. Microwave Theory Tech., Vol. 43, No. 4, 810-814, 1995.
doi:10.1109/22.375228

5. Piket-May, M., A. Taflove, and J. Baron, "FD-TD modeling of digital signal propagation in 3-D circuits with passive and active loads," IEEE Trans. Microwave Theory Tech., Vol. 42, No. 8, 1514-1523, 1994.
doi:10.1109/22.297814

6. Swanson, D. G. and W. J. R. Hoefer, Microwave Circuit Modeling Using Electromagnetic Field Simulation, Artech House, 2003.

7. Harrington, R. F., Time-Harmonic Fields, McGraw-Hill, 1961.

8. Railton, C. J. and J. P. McGeehan, "The use of mode templates to improve the accuracy of the finite difference time domain method," 21st European Microwave Conf., 1278-1283, 1991.

9. Celuch-Marcysiak, M., A. Kozak, and W. K. Gwarek, "A new efficient excitation scheme for the FDTD method based on the field and impedance template," IEEE Antennas and Propagat. Soc. Int. Symp., Vol. 2, No. 7, 1296-1299, 1996.

10. Craddock, I. J., D. L. Paul, C. J. Railton, P. N. Fletcher, and M. Dean, "Applications of single mode extraction from finite difference time domain data," IEE Proc.-Microwave and Ant. Propagat., Vol. 146, No. 2, 160-162, 1999.
doi:10.1049/ip-map:19990562

11. Gwarek, W. K. and M. Celuch-Marcysiak, "Wide-band S-parameter extraction from FDTD simulations for propagating and evanescent modes in inhomogeneous guides," IEEE Trans. Microwave Theory Tech., Vol. 51, No. 8, 1920-1927, 2003.
doi:10.1109/TMTT.2003.815265

12. Alexópoulos, N. G., "Integrated-circuit structures on anisotropic substrates," IEEE Trans. Microwave Theory Tech., Vol. 33, No. 10, 847-881, 1985.
doi:10.1109/TMTT.1985.1133145

13. Zhao, A. P. and A. V. Räisänen, "Application of a simple and efficient source excitation technique to the FDTD analysis of waveguide and microstrip circuits," IEEE Trans. Microwave Theory Tech., Vol. 44, No. 9, 1535-1539, 1996.
doi:10.1109/22.536601

14. Pozar, D. M., Microwave Engineering, 2nd edition, 1998.

15. Silver, S., Microwave Antenna Theory and Design, McGraw-Hill, 1949.

16. Van den Berghe, S., F. Olyslager, and D. De Zutter, "Efficient FDTD S-parameter calculation of microwave structures with TEM ports," IEEE Ant. and Progat. Soc. Int. Symp., Vol. 2, 1078-1081, 1999.

17. Elliot, R. S., Antenna Theory and Design, Revised edition, 2003.

18. Maloney, J. G., G. S. Smith, and W. R. Scott, "Accurate computation of the radiation from simple antennas using the finite-difference time-domain method," IEEE Trans. Ant. Propagat., Vol. 38, No. 7, 1059-1068, 1990.
doi:10.1109/8.55618

19. Schneider, J. B., C. L. Wagner, and O. M. Ramahi, "Implementation of transparent sources in FDFD simulations," IEEE Trans. Ant. Propagat., Vol. 46, No. 8, 1159-1168, 1998.
doi:10.1109/8.718570

Dr. Jeffrey Young

Dr. Ryan Adams