Quad-ridged dual-polarised square horn antenna
Image of the Quad-ridged dual-polarised square horn antenna.

Horn antennas occur in a variety of shapes and sizes, allowing them to be used in a wide range of applications. Some of these applications require dual-linear orthogonal polarisation with minimal interference between polarisations.

The horn antenna designed here makes use of quad ridges with two orthogonal feeds to achieve this dual polarisation. The feeding structure has the advantage of being able to support a fundamental propagation mode polarised in either of two orthogonal directions. This ability in turn supports a mode in virtually any polarisation (left hand circular, right hand circular, slant-linear, and dual-linear etc.).

Manufacturing of the ridges can be costly due to the tolerances required to obtain UWB operation. The antenna designed here is a more cost effective and simpler construction, while still achieving all of the above mentioned polarisation specifications. The trade-off, however, is that the operational bandwidth does not achieve the specification set out by the UWB definition.

A good reflection response and isolation between ports is achieved over a 25% bandwidth. This can be increased by tuning the ridged feed structure within the waveguide.

The polarisation-specific boresight gain varies between approximately 11 and 14 dBi across the band while maintaining a minimum cross polarisation of 15 dB. Good radiation pattern symmetry over the band is observed.

Total polarisation-specific gain at the minimum, centre and maximum frequency
Typical reflection and transmission coefficients versus frequency