Various types of antennas are used in various RF, microwave, and millimeter wave applications. One commonly used antenna in microwave and millimeter wave systems is the horn antenna, which has been in use since the early 20th century.
Essentially, a horn antenna is a rectangular or circular waveguide device with one end being small and the other end being large, either as a waveguide or coaxial port.
Horn antennas have the advantages of low voltage standing wave ratio (VSWR), wide operating bandwidth (for horn antennas, 10:1 or even 20:1 can be achieved), relatively simple construction, low manufacturing cost, and moderate directionality.
In addition, because the gain and VSWR curves of the horn antenna are very flat within the bandwidth range, it is very suitable for testing the performance of other antennas.
Horn antennas are commonly used as directional antennas in radar and microwave radiometers, as feed horns in large antenna structures such as parabolic antennas, and as calibration and test tools in testing other antennas. In addition, many new 5G test platforms and concept verification prototypes use horn antennas for their structural simplicity, and horn antennas are often used in channel measurements and other field test equipment. The horn antennas used in the above applications belong to different types and have different structures.
Conical horn antenna
This type of horn antenna is a common one, with the appearance of a rectangular or square (usually a rectangle) pyramid structure with the waveguide port as the end.
Sectoral horn antenna
The structure of this type of horn antenna has one side aligned with the end wall of the terminal waveguide port, and the other side gradually widens outward. Depending on the orientation of the widened side and the aligned side, the sectoral horn antenna can be divided into E-plane and H-plane sectoral horn antennas.
Conical horn antenna
Unlike the rectangular pyramid structure of the conical horn antenna and other horn antennas, the conical horn antenna is usually a conical or elliptical cone with a circular or elliptical end. The end of some conical horn antennas can also be rectangular.
Scalar horn antenna or exponential horn antenna
Unlike typical conical, sectoral, or conical horn antennas, this type of exponential horn antenna has side surfaces that gradually narrow in size in an exponential manner, forming a curved surface extending from the antenna opening to the waveguide end. This construction method maximizes the reduction of internal reflections and can maintain consistent impedance and electrical performance over an extremely wide bandwidth.
Corrugated horn antenna
The inner surface of the side wall of a corrugated horn antenna has transverse grooves perpendicular to the axis of the antenna. In electrical terms, the size of these grooves is smaller than the operating wavelength, which can achieve extremely low sidelobe levels and cross-polarization levels within the bandwidth of the antenna. This type of antenna is usually used for satellite and radio telescope applications.
Gain horn antenna
A standard gain horn antenna is a horn antenna that has a high gain that is relatively consistent over a wide bandwidth. This type of horn antenna is usually used to test other antennas in radar, satellite, and space applications.
Feed horn antenna
The waveguide feed horn is an antenna that is used to send and receive signals between RF and microwave electronic devices, satellite antennas, and radio telescopes.