A waveguide horn, or waveguide horn antenna, is an aperture antenna that uses a gradient transition of the conductive inner wall of the waveguide to the end of the horn in such a way that the waveguide port undergoes an impedance transition that matches with free space. This of course is frequency dependent, and the gradient of the waveguide horn has an impact on the antenna performance. A waveguide horn antenna can be made for every type of waveguide, square, circular, or elliptical.
The horn shape of a waveguide antenna can also be varied depending on the desired performance, namely directivity, gain, and antenna pattern. The purpose of the horn is to transform the planar electromagnetic (EM) wave within the waveguide to a curved wavefront better suited to free space propagation. The way in which a horn is flared impacted the directivity/gain, antenna pattern, and bandwidth of the waveguide horn. A horn can be flared out as a single slope, curved, or even a nonlinear flare (soft horn) with corrugations or other features. Typically, a wider flared horn will have a wider beamwidth, but will sacrifice gain/directivity to achieve this.
Modifications to a horn flare are to correct for undesirable antenna performance, such as pyramidal/rectangular horns producing significant sidelobes as a result of the phase error associated with the horn transition. Additional dielectric structures or conductive features can be added to a waveguide horn shape to modify the impedance and bandwidth properties of the horn. An example of this is a broadband waveguide horn antenna, which can be made to have a significantly higher bandwidth than a typical pyramidal or conical horn antenna.
Dielectric lenses can also be added to the end of the waveguide to transform the planar wavefront to a curved wavefront. These horn lens antennas can demonstrate higher gain/directivity than typical horn designs.
Waveguide Horn Antenna Types
- Standard Gain Horn
- Conical Horn
- Conical Gain Horn
- Lens Horn
- Broadband Horn
- Wide Angle Scalar Feed Horn
- Circular Scalar Feed Horn
- Dual Polarized Horn
- Dual Polarized Feed Horn
- Dual Polarized Scalar Feed Horn
- Omnidirectional Horn
- Probe (Probe Horn)
Waveguide horn antennas exhibit high gain and directivity, as well as high power handling and relatively high efficiency. This is why waveguide horn antennas are often used in high power applications and at very high frequencies. Waveguide horns are often found in test and measurement facilities, as well as deployed in sensing and satellite communication applications. Example use cases of waveguide horns include dielectric free space characterization, electromagnetic compatibility/electromagnetic interference (EMC/EMI) conformance testing, over-the-air (OTA) antenna testing, and more.