SEC: UNCLASS NEC-LIST:Modeling a conductive surface in NEC2

Scott ...

        There is a paper in the ACES Journal of Winter 1990 that addresses
this aspect of NEC:
        "Selecting Wire Radius for Grid/Mesh Models" written by L.A.
Oyekanmi and J Watkins.

        This goes on to discuss the "equal Area Rule", different proponents
giving the surface area of the bounding wires as:

* = surface area of modelled surface (Moore and Pizer "Method of
Moments in Electromagnetics" Research Studies Press 1984)
*

        * 2 X surface area of continuous surface (K.H.S. Lee, L. Martin and
J.P Castillo, "Limitations of wire grid modelling of a closed surface" IEEE
Trans Electromagnetic Compatability, Vol EMX-18, No 3, pp 123-129, August
1976)
* (parallel to one polarisation) = surface area of modelled surface
(G.J. Burke and A.J. Poggio "Numerical electromagnetic code (NEC) - Method
of Moments", Naval Ocean Systems Centre, San Diego, CA, NOSC Technical
Document 116, Jan 1981)
* 2 X surface area of a closed surface, or 2 X surface of an open
surface (P.G. Elliot and S.T. McBride, "Wire grid moment method (NEC) models
of a patch antenna" ACES Journal special issue 1989.)

    I have been using the "= surface area of modelled surface" of Burke and
Poggio for some time on helicopter fuselage modelling, and the odd checks I
have done give internal fields are well down (typically 15-20dB), indicating
that the mesh is behaving like a surface. Assigning diameters for arbitrary
mesh for this criterion is not a trivial task, and I developed an iterative
procedure which works well with triangular meshes.
 
    The same ACES Journal also has an excellent paper from Chris Trueman of
Concordia University entitled "Verifying wire-grid integrity with program
"Check". This discusses the NEC modelling guidelines in detail, and makes
good reading to both the novice and experienced NEC modeller.
 
    Perhaps a reprint of both these papers is in order, together with others
on similar coverage.
 
    On another subject, do any of our NEC-Listers have definitive writings
on the using the "Average Power Gain" to "fine tune" computed antenna gain
data??? On the RP card, setting the "D" of XNDA equal to 1 or 2 requests
computation of the average power gain over the region coverd by the field
points.
 
Cheeeeeeeeeeeeeeeeeeez
 
 
 
Alan Nott.

Alan Nott BEE, CEng, MIEE
Senior Technical Specialist Engineer
Electromagnetic Effects
Communications Command and Control Systems
Land Engineering Agency
Tel + 61 3 9622 2835
Fax + 61 3 9622 2959
email: alan.nott_at_defence.gov.au

-- 
The NEC-List mailing list <nec-list_at_gweep.ca>
http://www.gweep.ca/mailman/listinfo.cgi/nec-list