Experimental validation of numerical models for packaged MTL networks in non-plane wave external fields

Results are presented of recent efforts to develop and experimentally validate numerical algorithms for analysing the coupling of electromagnetic energy into printed circuit boards (PCBs). In the experiments, the PCBs contain multiconductor transmission lines (MTLs) and are placed in a perfect electric conductor (PEC) enclosure. Both full-field models, using the finite difference time domain (FDTD) and transmission line matrix (TLM) methods, as well as quasi-TEM models, using the MTL equations with forcing function terms, are investigated. Various test cases are considered in which a radiating monopole and a PCB, containing a microstrip, as the susceptible circuit, are placed inside a perfectly conducting box. Comparisons with experiment are made by first obtaining the numerically calculated response, at the near-end and far-end of the microstrip line resulting from the impulse excitation of the monopole. The experimental excitation pulse is then convolved with each of these responses to obtain a more accurate estimate of the induced voltage. As would be expected, the quasi-TEM approach requires considerably less computational resources but produces less reliable results for the complicated field distributions existing around the packaged PCB. Nevertheless the quasi-TEM approach has the advantage of being more easily interfaced with circuit simulators. This would be necessary if a complete circuit board were to be simulated