MICROWAVE REPEATER RESEARCH 



205 



ance/^ reflector antennas have difficult tolerance requirements imposed 

 upon them. For example, at 4000 megacycles, the 10-foot reflector must 

 conform to parabolic shape to within d= | inches, and any twist or warp 



1 



Fig. III-4. — Shielded metallic lens antenna. 



of the reflector greater than this would be objectionable. Lenses, however, 

 possess the property that a twist or warp in them does not impair their 



18 See, for example, "Radar .\ntennas", H. T. Friis and W. D. Lewis, B. S. T. /., 

 vol. 26, p. 219, April 1947, Figs. 17 and 28. 



