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BELL SYSTEM TECHNICAL JOURNAL 



further improvement in pattern of this lens over previous wave guide type 

 metal lenses is attributable to the absence of steps, as they tend to introduce 

 diffraction effects. The symmetry of the pattern also indicates a high degree 



l^'ig. 20 — Directional pattern of the lens of Figs. 8 and 16 when fed with a six-inch 

 stjuare electromagnetic horn. 



5 



DEGREES 



V^^ 



Fig. 21 — Directional pattern of the same lens when enclosed with a full horn shield. 



of homogeneity of the dielectric (the lens is 16 inches thick) ; this is a prop- 

 erty not always shared by ordinary dielectrics such as polystyrene. 



When a full horn shield is used, the illumination across the aperture has a 

 very strong taper (somewhat stronger than a cosine taper because of the 

 wide flare angle of the horn). This results in a very effective suppression of 

 the close-in side lobes as shown in Fig. 21. In the vertical plane, the side 



