|
:: Thin-wire Reciprocal Multiradius
Implementation of the Electromagnetic Moment Method
by Mark A. Tilston, PhD Dissertation, Dept.
Elec. Eng., Univ. Toronto, 1989
Abstract
The original version of the uniradius
thin-wire frequency-domain moment-method program developed by J.H.
Richmond has been re-formulated to suppress the computation of
non-physical asymmetric fields. Two alternative new versions are
described, termed the point-charge version and the bridge-current
version. The original program and the two new versions are
compared with each other and with simplified theory, where applicable,
on the following symmetrical structures: a rectangular wire loop, a
two-wire transmission line, a coaxial-cage transmission line, and a
log-periodic dipole antenna. The bridge-current version is shown
to be the most accurate, and the most invariant with respect to
variations in segmentation for the above structures. It is noted
that this version is particularly advantageous for structures that
include close-spaced parallel wires connected by short wire segments.
An implementation of the moment method for electromagnetic analysis of multiradius thin-wire structures,
including multiwire, multiradius junctions is presented. It is an
extension of the uniradius bridge-current reformulation of J.H.
Richmond's uniradius thin-wire theory described above. The method
features an exactly symmetric mutual impedance matrix ensuring
reciprocity between sources, it is unconstrained with respect to both
the length ratio and the radius ratio of adjoining segments, and it
permits the self-consistent inclusion of coaxial-cable sections in the
configuration under analysis. The method is validated (a) through
comparison with simplified theory and an alternative moment-method
analysis on both an electrically small rectangular loop and a short
coaxial cage transmission line, (b) through comparison with
transmission-line theory for a two-wire line and a coaxial cable, (c)
through comparison with measurements on a folded monopole antenna, a
sleeve monopole antenna, and a log-periodic dipole antenna, and (d)
through comparison with the uniradius bridge-current moment method and
transmission-line theory for a bazooka-balun-fed dipole antenna.
Comparison is made between the presented moment method, the NEC
(version #1) moment method, and the MININEC moment method, on the
analysis of a detuning stub used to minimize the reradiation of AM
broadcast signals from a sounded tower, and on the analysis of a bent
two-wire transmission line whose dimensions are typical of what one
would find on a printed circuit board. In these two specific
problems, the presented moment method is shown to be a significant
improvement over the NEC and MININEC moment methods.
Download:
Mark's PhD Thesis (2.2 MB) - I had to scan it as
I only have a hard copy.
|
|
