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Computation of far field

 
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sunil.pulinthitta
Antenna-Theory.com Newbie


Joined: 03 Jan 2011
Posts: 2

PostPosted: Mon Jan 03, 2011 6:16 pm    Post subject: Computation of far field Reply with quote

i saw the equations of near and far field of a horn antenna in the website.....i wish to get matlab code to compute far field from the aperture fields by fourier transform as you have mentioned..

Thank you
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bigSteve
Antenna Wizard


Joined: 14 Mar 2009
Posts: 265

PostPosted: Tue Jan 04, 2011 4:47 am    Post subject: Horn Antennas Reply with quote

I assume you are referring to the final equation on the horn antennas page:
http://www.antenna-theory.com/antennas/aperture/horn.php


To evaluate the equation using Matlab, you can do something like this (I haven't run this script, but it should give you the general idea for evaluating the radiation integral for the horn antenna):

% assume you have the aperture E-field distribution, Ea(x, y) which corresponds to your locations

integralSum = 0; % initalize discrete sum to represent integral
deltaX = A/100;
deltaY = B/100;
for x=-A/2: deltaX : A/2
for y=-B/2: deltaY: B/2
integralSum = integralSum + Ea(x, y)*exp(-j*k*(x*sin(theta)*cos(phi) + y(sin(theta)*sin(phi) )*deltaX*deltaY;
end
end

E(theta, phi) = integralSum*k/4/pi/r*(1 + cos(theta) );


That's basically it. You can declare phi to be constant and have theta a vector (then you have a theta cut), or do vice-versa and you have a phi cut. The trick is to simply write the integral as a discrete sum, and get the result point by point.

For more on Fourier Transforms, see: http://www.thefouriertransform.com
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sunil.pulinthitta
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PostPosted: Mon Jan 10, 2011 4:44 pm    Post subject: Reply with quote

thanks for the reply.....too much to ask but can u tel me what i should sub in place of Ea(x,y).......Emaxhorn*cos(pi*x/A)*exp((-1i)*(k/2)*((x^2/le)+(y(l)^2/lh)))....wil this do?.......im gettin an answer but then i dono if ots right.....128v/m at 10m.....
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kviksand81
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Joined: 18 Dec 2014
Posts: 3

PostPosted: Tue Dec 30, 2014 8:03 pm    Post subject: Reply with quote

sunil.pulinthitta wrote:
thanks for the reply.....too much to ask but can u tel me what i should sub in place of Ea(x,y).......Emaxhorn*cos(pi*x/A)*exp((-1i)*(k/2)*((x^2/le)+(y(l)^2/lh)))....wil this do?.......im gettin an answer but then i dono if ots right.....128v/m at 10m.....


How did the progress with the "project" turn out? I'm a bit curious to know, since I'm doing a similar project myself so I would be happy to know any experiences you've made!

Best Regards,
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