Design a microwave horn antenna and make it by 3D printing
On the microwave bands, horn antennas are the standard antenna for beacons, narrowband links and as feeds for dishes. Signal-Pirat designs the optimum-gain pyramidal horn matching the rectangular waveguide, checks whether the printing process is fine enough for the frequency, and exports the horn as an STL file.
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What the page does
- Bands from 5.7 GHz to 241 GHz with matching rectangular waveguide
- Aperture, axial length and beamwidth for a target gain
- TE10 cut-off, operating range and guide wavelength
- Skin depth, minimum metallisation thickness and extra loss from roughness
- STL file with waveguide section and flange plate
Background
A pyramidal horn reaches maximum gain for a given length when the aperture phase error is about a quarter wavelength in the E plane and three eighths in the H plane; aperture efficiency is then about 51 %. A rectangular waveguide carries only the fundamental TE10 mode between about 1.25 and 1.9 times the cut-off frequency c/(2a). Printed plastic horns need a conductive inner layer of several skin depths; at 10 GHz the skin depth in copper is about 0.66 µm. Measurements of printed horns in Ka and D band show gains up to about 3 dB below metallic reference horns, mainly due to surface roughness.
In practice
How it works: choose the band, enter the target gain and read the dimensions. Then choose printing process and conductive layer: the page shows whether the tolerance suits the wavelength and how thick the metallisation must be. The STL file contains the hollow horn with flange plate; drill the hole pattern according to the flange standard.
Frequently asked questions
Which printing process is sufficient for 10 GHz?
At 10 GHz the wavelength is about 29 mm; filament printing with about 0.2 mm tolerance is sufficient if the inner surface is smoothed and metallised.
What is the D band?
The waveguide range from 110 to 170 GHz (WR-6). It contains the amateur bands around 122 GHz and 134 GHz.
May I transmit with the horn antenna?
Only with an amateur radio licence and in the amateur band under the amateur radio regulations in force. Receiving is possible without a licence.