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can power radiated be measured in the near field?

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kae_jolie

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A dipole array is boxed in a rectangular box similar to radiation boundary box in HFSS. It radiates at 915MHz. The wavelength at 915MHz is 32cm. The far field is > 16cm. Can the power radiated be measured, say at 10 cm (in the near field) right outside the rectangular box assuming rectangular box is 10cm wide and long?

Would the power radiated measured at 10cm (near field) be different than power radiated at 20cm (far field)? I know the radiation pattern would be different but would the power radiated be different, as well?

Thanks.
 

Yes the radiated power would be different this is due to close in coupling of your probe (capacitance coupling and what not). However if you scan over the entire volume in the near field it is possible to extract the far field radiation patter as well as how much power is being radiated in a specific direction.

Here is a good paper from Agilent explaining how near field and far field radiation are different:
http://www.home.agilent.com/upload/cmc_upload/All/NSI-near-far.pdf

Hope this helps
 
kae_jolie said:
The far field is > 16cm.
Click to expand...

Far Field > 2D*D / lambda; where D is the largest dimension of antenna. This far field distance is also called Fraunhofer's distance I suppose.

The near field can be measured for sure using a 2 port VNA.
 

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