Several K a-band spatial-amplifier power combiners and their free-space fee
ds were characterized using a high-resolution extreme-near-held electroopti
c measurement technique. The two-dimensional electric-field amplitude and p
hase maps obtained from several arrays are presented. The usefulness of the
technique for diagnostic purposes during the design and prototyping stages
of the active arrays is discussed, In particular, the electrooptic maps we
re shown to be valuable for making improvements in the bias line design in
one case, and for isolating faulty unit cells in another case.