The Model for Studying Surface Waves

We shall next study surface waves on active arrays with a finite FSS ground-plane. Our model will be similar to the one used in the previous section—except that in order to properly study surface waves, the model must be considerably wider. 

The fundamental problem is now that all finite periodic structures may exhibit strong presence of surface waves at least at some frequencies as discussed in Chapter 4. We may envision that the finite FSS groundplane alone shows surface waves in one frequency band and the active array possibly in another. However, when the active array is placed adjacent to the FSS groundplane, we would expect both of these frequency bands to change and, possibly, to degenerate into a single frequency band. From a practical point of view, it is of course the surface waves on the combined structure that are most important. 

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