Open boundary quad ridged horn
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Image of the Open boundary quad ridged horn. |
The open boundary quad ridged horn is popular in EMC compliance measurements, and is often used when measuring radiation patterns of test antennas in an anechoic chamber.
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Total gain 3D patterns at (a) fmin, (b) 2 x fmin, (c) 3 x fmin, (d) 5 x fmin and (e) 9 x fmin. |
Although the antenna may be seen as a variation of the Quad ridged pyramidal horn, the propagating mode supported by the quad-ridged structure changes from TE (with sidewalls) to quasi-TEM when the sidewalls are removed. The operation mechanism or the antenna is therefore better understood by considering two planar Vivaldi antennas placed orthogonally to each other with co-located feed points.
A major advantage of removing the sidewalls is that the on-axis gain dips prevalent in classic quad-ridged horns with sidewalls are eliminated - though the overall gain is generally reduced.
The designed antenna achieves a VSWR below 3:1 over a 9:1 bandwidth with a relatively stable on-axis gain, especially considering its compact nature. At the upper end of the band the pattern shape does degrade to some extent. The gain typically varies between approximately 8 and 14 dBi across the 9:1 band.
The antenna may be divided into two distinct sections — a coaxial-to-ridged-waveguide transition as well as a flared ridge section. The feed section aims at proving a good return loss for both vertical and horizontal polarization.
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Typical VSWR behaviour versus frequency. |