Feed horn

The feed horn minimizes the mismatch loss between the antenna and the waveguide.

When used with a offset, parabolic or lens antenna, the phase center of the horn is placed at the focal point of the reflector.

The feedhorn then connects via a short waveguide to the "low-noise block downconverter" (LNB), a small housing containing a part of the reception electronics (also called the "RF front end").

This LNB converts the high satellite microwave downlink frequencies to lower frequencies, so the TV signals can be more easily transmitted through coaxial cables to receivers located anywhere inside a building.

Feedhorns are also used in applications like radar, line-of-sight microwave transmission or radio astronomy.

Feed horn with concentric rings (left) and LNB (right) on a Hughes DirecWay home satellite dish.
An LNBF ( LNB with integrated feed horn) that has been cut into two. Visible is the scalar horn antenna (the funnel with concentric rings), which couples the microwave beam into a short waveguide (the tube connecting the feed horn to the LNB electronics part of the LNBF).
Feed horn (right) on a military radar antenna. The feed horn must be shaped to produce a radiation pattern tailored to adequately illuminate the reflector.