With a LENS ANTENNA you can convert spherically radiated microwave energy into a plane wave
(in a given direction) by using a point source (open end of the waveguide) with a COLLIMATING LENS.
A collimating lens forces all radial segments of the spherical wavefront into parallel paths. The point
source can be regarded as a gun which shoots the microwave energy toward the lens. The point source is
often a horn radiator or a simple dipole antenna.
The WAVEGUIDE-TYPE LENS is sometimes referred to as a conducting-type. It consists of
several parallel concave metallic strips which are placed parallel to the electric field of the radiated energy
fed to the lens, as shown in figure 3-10A and 3-10B. These strips act as waveguides in parallel for the
incident (radiated) wave. The strips are placed slightly more than a half wavelength apart.
Figure 3-10A.Waveguide lens.