Feed and subreflector alignment in a Gregorian compact range [radar]

A dual-chamber Gregorian compact Experimental Test Range (ETR), which is currently in use with a 16-ft blended rolled-edge main reflector has been built. The Gregorian system adds complexity to compact ranges already sensitive to alignment criteria. The task of creating a procedure for aligning and focusing a subreflector system is addressed. The following sequence was realized: (1) alignment of the prober with the main reflector; (2) prime focus-fed adjustment for main reflector focal point location; (3) coarse feed-subreflector alignment; (4) backward and forward scattering measurements with a 1-in sphere at the subreflector focus to finely tune the feed location; (5) coarse subreflector-main-reflector alignment based on results from (2) and (4); (6) cross range alignment; (7) system focusing; and (8) an optimal main reflector illumination adjustment