This feed was designed and constructed by the Millimeter Wave
Laboratory of the Raman Research Institute. It is of the corrugated horn
type - known for its high aperture efficiency and very low cross-polarization
levels. In any horn, the antenna pattern is severely affected by the
diffraction from the edges which can lead to undesirable radiation not only
in the back lobes but also in the main lobe. By making grooves on the walls
of the of a horn, the spurious diffractions are eliminated. Such horns are
called ``Corrugated horns''. Our feed at 1420 MHz. has fins instead
of grooves, since the whole assembly is made out of brass sheets. The
flare-angle of the horn is . The dimensions of the feed
Radiation patterns, including the cross-polar pattern is shown in Fig 19.16.
The edge taper is dB and the cross-polar peak is dB. The front-end electronics is housed in a rectangular box,on the back side of the horn, forming one integral unit. The entire band is divided into 4 subbands, each 140 MHz wide and centered on 1390, 1280, 1170 and 1060 MHz. There is also a bypass mode in which the entire bandwidth is available.