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BELL SYSTEM TECHNICAL JOURNAL 



beam-forming properties, and, with the development of metal lenses for 

 microwaves, ^^ this type of antenna appeared to lend itself very well to re- 

 peater applications. The "shielded" type lens, which is a lens in the mouth 

 of a short horn, is shown in Fig. III-4. This antenna, which was developed 

 for the New York-Boston circuit,* possesses the property of excellent 



Fig. III-5. — Internal view of lens for the shielded metallic lens antenna. 



crosstalk suppression both side to side (85 db) and back to back (125 db). 

 Within the horn, the small amount of energy reflected back from the lens 

 is directed away from the feed by tilting the lens, a procedure which does not 

 noticeably affect the I'adiation characteristics, but which results in a fairly 



i» W. E. Kock, Metal Lens Antenna, Proc. I. R. £., vol. 34, p. 828, November 1946. 

 * Developed by W. E. Kock and R. W. Friis. 



