Basics of Waveguide Antennas

A waveguide antenna is a type of antenna that channels RF energy from an air medium into a waveguide, or vice versa. Once the RF energy has been captured, it is either conducted through waveguide interconnect, or picked up by a coaxial interface to later be transmitted through a coaxial assembly. The reverse is also true, as waveguide antenna are symmetric systems. The range of frequencies and antenna polarization depend on the size and type of waveguide antenna, of which there are many standard forms. Much like with any antenna, the following parameters are key when selecting a waveguide antenna.

Important Waveguide Antenna Parameters

•  Frequency Range (waveguide band or coaxial bandwidth for broadband waveguide antenna)
• Gain
• Beam Width (Horizontal Beam Width)
• Beam Height (Vertical Beam Width)
• Impedance
• Input VSWR
• Antenna Pattern
• Polarization
• Interface (Coaxial or waveguide)
• Size
• Weight
• Input Power Handling

Waveguide antennas are also limited in frequency by the size of waveguide internal to the antenna, as well as the antennas physical dimensions. In some cases, such as with broadband antenna with a coaxial interface, the frequency range is limited by the design of the antenna and the coaxial interface. In general, the strengths of waveguide interconnect, such as high power handling, enhanced shielding, and low loss, are also shared with waveguide antenna with the exception of waveguide antenna with coaxial interface. Moreover, waveguide antenna frequency operation is also dependent on physical dimensions, and lower frequency waveguide antenna tend to be impractically sized for many applications.

There are several varieties of waveguide antenna, each with their specific advantage for a given set of applications. The commonly available varieties are included in a list below:

Waveguide Antenna Types

• Standard Gain Horn
• Conical Horn
• Conical Gain Horn
• Probe
• Lens Horn
• Sector
• Omni-directional
• Broadband Horn
• Wide Angle Scalar Feed Horn
• Circular Scalar Feed Horn
• Dual Polarized Horn
• Dual Polarized Feed Horn
• Dual Polarized Scalar Feed Horn

Waveguide Standard Horn Antenna, Conical (Circular) Horn Antenna, Exponential (Scalar) Horn, & Sector (Sectoral or Wide Angle) Horn Antenna

A horn antenna is a waveguide antenna with a flaring metal shape that resembles a musical horn, hence its name. Horn antennas are directional antennas that are either rectangular (standard or pyramidal horn) or circular (conical) in nature. These shapes lead to varying polarizations, either linear or circularly polarized. A horn antenna can also be designed with curved sides, which can have a pyramidal or conical cross section. This design allows for minimized internal reflections and near constant impedance over a wide frequency range. Sectoral horns are also possible with one side of a pyramidal horn being parallel instead of flared, which produces a fan-shaped beam pattern.

Waveguide Gain Antenna

The low loss of a waveguide antenna allows for ints directivity to be almost equal to the antenna’s gain. Hence, these antennas may exhibit a high gain if the directivity of the antenna is very narrow, which is determined by the shape and size of the antenna.

Waveguide Probe Antenna

Waveguide probe antennas are generally designed for sampling radiated electromagnetic fields of an antenna under test while only minimally disturbing the incident field. They are often used to measure the near-field of test antenna structures.

Waveguide Lens Antenna

A lens antenna uses the properties of a lens (convergence and divergence) to focus the RF energy captured by a waveguide antenna to a point source, which is typically a coaxial probe (receptor) with a waveguide antenna as the feed antenna. Lens antennas are generally used in applications that require wide bandwidth and highly directive antenna.

Waveguide Omni-direction Antenna

An omni-directional waveguide antenna is designed in such a way that the antenna pattern radiates in 360 degrees, as opposed to a fan-shape or single lobe with horn antennas.

Waveguide Broadband Antenna

A broadband waveguide antenna is designed in such a way to direct RF energy over a wide bandwidth to an interface receptor (typically coaxial) that can handle the desired bandwidth of the antenna. The design consists of exponential sloping waveguide sides and possibly inserts that enable the wide bandwidth operation.

Waveguide Feed Antenna

A feed antenna is used to direct RF energy to another antenna or receptor. Hence waveguide antennas are sometimes called feed antennas or feed horns depending on the type of waveguide antenna.

Waveguide Dual Polarized Antenna

Dual polarized waveguide antenna are designed to support both linear and elliptical polarized waveforms.

Learn more about Pasternack’s Expansive line of Waveguide Antennas