The Finite Array Case Excited by Generators

To summarize No energy is radiated from the infinite array, only from the finite. Thus, a test antenna located a reasonably large distance from the array will pick up a signal only from the finite array, not the infinite. Furthermore, from the law of reciprocity we may conclude that a signal from the test antenna cannot produce a surface wave on the infinite array but can readily do so on the finite array. 

Because of the lossy component of the scan impedance, the waves on the finite array can be considered as being surface waves for a slightly lossy periodic structure. 

5 THE ELEMENT CURRENTS ON A FINITE ARRAY EXCITED BY AN INCIDENT WAVE 

We now return to our original problem, namely, where a finite array is exposed to an incident field rather than fed by voltage generators at each terminal. 

SURFACE WAVES ON PASSIVE SURFACES OF FINITE EXTENT 

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