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Far Field of Array with Parabolic Reflectors

 
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TUD
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Joined: 11 Feb 2010
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PostPosted: Thu Feb 11, 2010 3:33 pm    Post subject: Far Field of Array with Parabolic Reflectors Reply with quote

Dear All,

if I have an array of 4 Parabolic Reflectors with elements spacing of 100lambda, where starts Far Field of this array?

in the far field of each parabolic antenna or in the far field of array?

thanks in advance.
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admin
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Joined: 03 Jan 2007
Posts: 203

PostPosted: Fri Feb 12, 2010 4:29 am    Post subject: Reply with quote

The far field is where the radiation from each antenna falls off as 1/r^2 and the phase appears linear.

Your application is quite odd, so you probably won't find the answer in a textbook. I actually think the exact answer is open to interpretation.

But for me, the far field of that array is the region where you are in the far field of each antenna. This means the far field region will not be a simple region, but one with holes centered around each antenna.

The very conservative answer is you should be in the far field assuming the antenna is the size of the array, but I think the array will act like an array even between the elements, given the large spacing.
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TUD
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PostPosted: Fri Feb 12, 2010 12:28 pm    Post subject: Reply with quote

Thank you for your answer.

For example, if we take reflect array. In the far field formula "D" is a maximum dimension of an array (the largest side of array) and it doesn't matter if the size of the patch is equal to the cell size (fit in the cell) or is smaller than the cell. If smaller we have also "holes" but this fact doesn't play any role for the far field calculation.

but the difference is that the patches reradiate the received power and the parabolic antennas only reflect it and dont reradiate.

I don't know, does this difference play a role for the FF calculations?
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Schubert
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Joined: 08 Apr 2009
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PostPosted: Tue Feb 16, 2010 5:52 am    Post subject: Reply with quote

Your comment:
"ut the difference is that the patches reradiate the received power and the parabolic antennas only reflect it and dont reradiate. "

- doesn't make any sense.
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TUD
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Joined: 11 Feb 2010
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PostPosted: Tue Feb 16, 2010 7:56 am    Post subject: Reply with quote

Schubert wrote:
Your comment:
"ut the difference is that the patches reradiate the received power and the parabolic antennas only reflect it and dont reradiate. "

- doesn't make any sense.


Tnaks for your comment.

Do you mean that there is no difference?
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