RE: NEC-LIST: Antenna pattern distortion modelling

   The point about GTD (or UTD) formulations in a code
   is specifically that it will take LESS COMPUTER
   RESOURCES than a strict MoM formulation. (The assumption
   here is that the MoM is the mathematically exact solution
   to the appropriate EM boundary value problem.)

   From a computational viewpoint, this is the specific
   advantage of the GTD (meaning semi-/quasi-analytical)
   formulations, whose accuracy can be shown to increase
   with electrically large scatterers.

   The 1.9 GHz is probably not a magic number; it maybe the
   frequency at which the electrical sizes of the antenna or
   scatterer are such that both GTD and MoM results can be
   obtained and mutually compared with modest resources.
   
   As an example, if there is a lamba/2 dipole at say 1*lambda
   away from a square conducting plate whose size varies between
   10 and 20*lambda, then MoM solutions will take significantly
   more c.p.u time than a pure GTD solution. (This lambda can now
   be the wavelength at 1.9 GHz or 500 MHz or 10 GHz.)

 *******************************************************
              Deb Chatterjee, Ph.D.

       Assistant Professor, ECE Department,
  University of Missouri-Columbia/ Kansas City (UMKC)
  370-H Robert H. Flarsheim Science & Technology Hall
  5100 Rockhill Road, KC, MO 64110-2499
  tel.(816)235-1276 || fax (816)235-1260
  e-mail: chatd_at_umkc.edu

-----Original Message-----
From: KLysiak_at_swri.edu.spam [mailto:KLysiak_at_swri.edu.spam]
Sent: Tuesday, September 21, 1999 8:12 AM
To: nec-list_at_ee.ubc.ca
Subject: re: NEC-LIST: Antenna pattern distortion modelling

>From the desk of Keith Lysiak <KLysiak_at_swri.edu>

        I use NEC regularly to model DF systems in the HF\VHF\UHF
frequency ranges with very good success. I have modeled cellular and
PCS applications up to 1.9GHz with good success. DF applications
typically require both accurate amplitude and phase comparisons.

        There are various distinct advantages of one method (GTD vs
MoM) over the other but both have their applications and practical
uses. With adequate computer resources, both should be able to
provide good results when properly applied in this frequency range.
Received on Mon Sep 27 1999 - 15:49:50 EDT