Various approaches to validating full wave simulations

It is never enough to simply "believe" a model has created the correct answers; engineers must be able to prove it by validating the model. Simulation is usually performed on a computer, and the old phrase "garbage in, garbage out (GIGO)" still applies. Engineers should validate their models to ensure the model's correctness, and to help understand the basic physics behind the model. Models can be validated by a variety of techniques. Which technique is the best to validate a specific model depends on a number of parameters, and must be decided on a case-by-case basis. Measurements can be used to validate modeling results, but extreme care must be used to ensure the model correctly simulates the measured situation. Omitting feed cables, shielding or ground reflections, or different measurement scan areas can dramatically change the results. An incorrect model result might be indicated when, in fact, the measured and modeled results are obtained for different situations, and should not be directly compared. Multiple simulation techniques applied to the same model is a good way to ensure the correct physics are included in the model, and that the appropriate physics are modeled correctly. Care is needed to insure that the modeling techniques are different enough to ensure a meaningful comparison is made. Intermediate results can also be used to help increase the confidence in a model. Using the RF current distribution in a MoM model, or the animation in an FDTD model, can help ensure the overall results are correct by determining the intermediate results are correct. These intermediate results have the added benefit of increasing the engineer's understanding of the underlying causes and effects of the overall problem. There are a number of other possible validation techniques, including using known quantities, model parameter variation, etc. These various possibilities depend greatly on the exact model and the goal for the simulation. The bottom line is that engineers need to understand the physics of the problem at-hand and to ensure the results can be shown to be correct. Regardless of the accuracy of the modeling tool for 'other' models, each modeling exercise must have some level of validation before the simulation results can be trusted. This does not mean that each and every model must be validated, but each group of models or each series of models for similar problems must have some level of validation.