METALLIC DELAY LENSES 



69 



This extremely close spacing and the staggered arrangement of strips cor- 

 respond to a heavy capacitative loading and introduced so much delay per 

 unit length that the measured effective dielectric constant of this lens proved 

 to be 225 (i.e. the index of refraction was 15). Because of such a high 

 dielectric constant the reflection losses at the surface of this lens are high, 



"■'W 



Fig. 12— Lens formed by metal-spraying tin directly onto polystyrene foam sheets. 



SO that, for efficient operation, tapered or quarter wave matching sections on 

 each surface would be necessary. 

 (e) Frequency Sensitive Delay Lenses 



When the conducting elements approach a half wavelength in their length 

 parallel to the electric vector, resonance effects occur and the artificial 

 dielectric behaves like an ordinary dielectric near its region of anomalous 



