Re: Need Near Field equations problems
From: Roy Lewallen (w7el_at_eznec.com)
Date: 11/14/04
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Date: Sun, 14 Nov 2004 17:59:24 +0000 (UTC)
curiousjohn4 wrote:
> Could someone please provide a correct near field equation that a
> computer programmer can understand? I'm using the following equation
> in a simple simulation but it's not working in all cases.
>
> E = a * sin(theta) * q / ( 4 * pi * e * c^2 * r )
I don't know where you got that equation, but I'm not surprised it's not
giving the right answer. In the near field, there are components
inversely proportional to r, r^2, and r^3. The equations are too complex
to easily write in ASCII, and the terms require some definition. But you
can find the relevant equations in Jordan & Balmain, _Electromagnetic
Waves and Radiating Systems_, eq. 10-41 and 10-42; Kraus,
_Electromagnetics_, eq. 13-49 and 13-50; Johnk, _Engineering
Electromagnetic Fields and Waves_, eq. 11-41a and 11-41b; or most other
electromagnetics and some antenna texts. Note that two equations are
given, one for the radial component and another for the circular (theta)
component, which decay at different rates as the distance from the
current element increases.
Roy Lewallen, W7EL
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