  In this publication we continue our previous work on extending the angular
scan range of phased arrays using metasurfaces. We consider in detail scan
enhancement using a single metasurface lens in the near-field of a source and
provide analytical expressions for source excitation to obtain a desired beam.
We show that such a device suffers from the same directivity degradation as in
the case of far-field lens placement. Moreover, we discuss in detail that this
approach has limitations, and one cannot place the lens arbitrarily close to
the source array. We then propose a two-lens near-field scan enhancer which is
not subject to the same limitations, although still subject to the same
directivity degradation. Finally we propose a binary metasurface concept which
theoretically achieves desired scan enhancement without directivity
degradation. Some theoretical claims are then verified via full-field
simulations.
