[MLB-WIRELESS] Circular waveguides (cantennas)

[Julian Featherston]

G'day all

I've used the calculations in the ARRL Antenna book 19ed. To generate
the theoretically optimum and the acceptable range of dimensions (for a
plain tube with one closed end) - available in simplified form here
http://www.concentrate.com.au/misc/circular_waveguide_optimise.xls in
excel 97-2000 format.

Next task is making one at the optimum dim's
If one requires a larger aperture (and more gain) it seams best to mount
a conical horn to the end of this optimum "can".

There is also the possibility to add a disc for unifying the "amplitude,
relative to unity on axis" for TE and TM planes. In English that is - if
the illumination is not uniform for TE and TM planes, one can broaden or
narrow the TM plane by adjusting the spacing of this disc to the
aperture (open end).
A disc 229.1mm in diameter is enough. If you were using a 90mm diameter
can you would remove a 90mm hole from the middle of the disc and mount
to the outside of the can. This is only going to make a 1 to 2 dB
difference.


Jules
 


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