
332 Microwave Engineering
Figure 9.19. This lens delays or slows down the propagating wave as it
passes through the lens. The phase delay in the passing wave is determined
by the refractive index that is related to the dielectric constant (n = √
ε
) of
the material. In most cases, articial dielectrics, consisting of conducting
rods or spheres that are small compared to the wavelength, are used to
construct delay lenses. Owing to contours of the lens, the inner portion of
the transmitted wave is decelerated for a longer interval of time than the
outer portions. Such a non-uniform delay causes the radiated wave to be
collimate