"a" wrote in message
...
Hi "a"
Just a thought -- I think you are concerned with the radiation from
the illuminator adding to (or canceling) the radiation from the
reflector. Normally, the illuminator is designed to establish a pattern
that aims only toward the reflector. But, since you dont wish to shape
the radiation pattern from the illuminator, you might want to consider
that the total pattern from both the illuminator will depend on how big
the reflector is (in wavelengths).
If the parabola is large, the half of the illuminator's radiation in
the "wrong" direction wont seriously effect the total pattern, and can be
ignored. You might assume the radiation from the reflector is
concentrated to be within a 20 degree wide sector (20 dB gain antenna).
The radiation from the illuminator in that 20 degree sector is so weak
that it will not be noticeable.
The fact is - There are many factors that a designer of parabolic
antennas considers. Google
Jerry
Hi Jerry,
Thanks, yes the adding/canceling was what I was trying to address.
I'd Googled on the subject but couldn't find anything that answered that
point. I did come across some interesting sites that described the need to
illuminate the whole of the reflector to make good use of its full dish
size (and hence minimise beamwidth), but I was trying to keep mine simple.
Treating it simplistically, I guess that, for a given diameter, a deep
parabola (ie the focus well inside the paraboloid) will capture more of
the radiated energy and redirect it in the required direction, than a
shallow parabola would.
I was thinking that I would go for a sheet of aluminium bent into a 2-D
parabola, about 2.5 wavelengths across, giving me a beamwidth of around
0.5 radians Presumably a 2-D parabola would only have gain in 2-D, and it
would be about 2*pi/0.5 = 12, (11dB over a whip).
For a 2.4GHz signal this equates to a parabola 31cm across.
Hi "a"
I saw
http://www.nodomainname.co.uk/parabolic/parabolic.htm on Google
and thought it fit your line of interest. It appears that your goals are
realistic and dont require extensive research on the design of parabaloids.
Try Googling again and see if you cant find some data on WiFi, instead of
parabola antenna design. I have seen many WiFi antenna designs that use
kitchen pots and pans as the reflectors.
Jerry