Testing Technique and Verification of ChaoWei Antenna Group
The feed systems we always see can be divided into four types:Front feed, Offset feed,Cassegrain and Gregorian.(Red part stands for reflecting surfaces; Green stands for
feed antenna; Blue stands for typical supporting structures; and Black stands for a few typical rays.). The details of them are as below:
1. Front feed(or Axial feed): This type of feed always locates at the center of the dish, which is on the beam axis and at the focal
point of antenna. It is the most common type, but has a disadvantage that the feed and its supports will block the beam patially.
Please refer to the Fig.1 below:
2.Offset feed(or off-axis feed): This type of feed is located at one side of the reflector, not with symmetric primary reflector. As it
is outside the beam area, it can avoid obstructions to the beam. It is always used in home satellite dishes. Please refer to the Fig.2
below:
3. Cassegrain design: This kind of feed is located on or behind the dish. At the dish focus, the beam illuminates a small hyperboloidal
secondary reflector, which reflects the beam back to the parabolic dish. It is often used in large antennas or antennas with complicated
feeds, such as satellite ground antennas and radio telescopes. Please refer to the Fig.3 below:
4.Gregorian design: This kind of feed looks like the Cassegrain type. Their difference is Gregorian has a concave ellipsoidal shape on
the second reflector.Please refer to the Fig.4 below:
Reference: Diagram showing the most common types of parabolic antenna feeds. (https://commons.wikimedia.org/wiki/File:Parabolic_antenna_types2.svg)
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