Planar Wave

Hi

What shuould be distance(in landa) of a source to an receiver antenna, to become impinging waves planar?

hello,

isn't this the same as the far field condition used in e.g. antenna measurements?

best regards

for far field condition:

L ≈ 2D2/λ

L is the measure distance , D is the antenna dimension

λ is the wavelength .

Hi

Length of antenna(monopole) is 1 meter and wavelength is 2 meter, so according to your formula L is less than 1 meter.
I think it is wrong.:D

this depends on the size of receiver.

Hi

What do you mean by size of receiver?

the formula could be found in electromagnetic book ,

I think it mentions that if L is large enough , and it could be

identified a far field.

L >> 2D2/λ

Well, you can not achieve a real plane wave. But you can create an approximation to it. What you need is an electromagnetic wave whoose amplitude and phase does not vary over a certain area. So the distance required to obtain such an approximation does depend on the size of the antenna or the aperture of the antenna.

Thanks irfan1

Suppose i have a 1m monopole antenna on top of a car, transmitter frequency is 140MHz and the eviroment is reflection free, what should be the distance from transmitter to receiver?

thnks in advance.