Wimpie wrote:

Hello,

Your formula for far field distance (Fraunhofer region) assumes a path
difference between the inner and outer antenna with respect to an
observation point of 1/16 lambda.

Someone has said that the formula I gave is not valid for a phased array.

His comment (about the 2 D^2/lambda) is below:

-----
That estimation does not apply in this case. It can be considered to be
valid for aperture antennas which is not the case here. It would only
require to have the transmitting antenna illuminating the pleased array
within its 3dB mainlobe which of course is by far the case at a distance
of 3000m or even more.
------


I'm not to bothered about the odd factor of two. I have seen a
derivation of the formula, but it was based on a rectangular aperture,
not an array of them. It don't know if that may mean the equation is
just not appropriate at all.


Using that forumal puts the far-field distance at about 10 km in my
case. Using someone elses idea, puts it at only a few hundred meters.
There is at least a factor of 10 difference.
--
Dave (from the UK)

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