Figure 3-11.Delay-type lens.
Loaded Microwave Lens
The LOADED MICROWAVE LENS, shown in figure 3-12, is a multi-cellular array of thousands of
cells. Each cell contains a slow-wave (delayed), serrated-metal, plastic-supported waveguide element
which acts as a phase-controlling device. A loaded lens can focus microwave energy in much the same
way as the waveguide type. The reason is that the speed of propagation is higher in the region between
parallel plates than in free space. The parallel plates support the cells.
Figure 3-12.Loaded lens.
The lens shown in figure 3-12 has an egg-crate appearance because it is really two lenses occupying
the same volume. Vertical plates make up a lens that focuses a vertically polarized beam, and horizontal
plates handle beams which are horizontally polarized. In other words, this type of construction can be
used in multiple-beam applications where the polarization of the beams is different.
Q-12. What is the purpose of a collimating lens?
Q-13. How does a waveguide-type lens focus spherical wavefront microwave energy?
Q-14. What type of lens decelerates a portion of a spherical wavefront?