SuperNEC
UTD Technical Reference Manual
Version 2.7
Document
Status: Release
SuperNEC
UTD Technical Reference Manual
Version 2.7
Document
Status: Release
A1.Table of Contents
2. Computations
specific to plates
3. Computations
specific to cylinders
3.1. Radius of
curvature in the principal planes
3.2. Radius of
curvature in plane of incidence.
3.3. Finding the
length of a geodesic path
4. Computations
specific to diffraction
4.1. The
diffraction transition function.
5. UTD
diffraction off a wedge
5.1.1. The UTD edge diffraction coefficients
5.1.3. The 3D distance parameters
5.1.5. Computing the diffracted wavefront radii
6. UTD slope
diffraction off a wedge
6.1.1. The UTD slope diffraction coefficients
7.1.1. The UTD corner diffraction coefficients
7.1.3. The corner distance parameter for spherical
incidence
8. UTD reflection
off a cylinder
8.1.1. The UTD reflection coefficients
8.1.2. The 3-D distance parameters
8.1.3. The 3D spreading factor
8.1.4. Computing the reflected wavefront radii
9. UTD
diffraction off a cylinder
9.1.1. The UTD diffraction coefficients
9.1.2. The conservation of energy term
9.1.3. The 3-D distance parameters
9.1.4. The 3-D spreading factor
9.1.5. Computing the diffracted wavefront radii
9.1.6. Evaluating the transition function
9.2. The UTD
equation for grazing incidence.
9.2.1. The UTD diffraction coefficients for grazing
9.2.2. Computing the grazed wavefront radii
SuperNEC (SNEC) is an object-oriented version of the FORTRAN program NEC-2. This technical manual is therefore very similar to the NEC-2 manual. In fact, many sections have been copied verbatim from the NEC-2 manual. The reason this document has been produced (as opposed to referring the reader to any readily available NEC-2 manual) is because new theory will be added to SNEC and some features that exist in NEC-2 will not be implemented in SNEC. The easiest way of keeping an up to date reference of the theory implemented in SNEC is to start with the an electronic version of the NEC-2 manual and modify the document as the SNEC code evolves. Many extensions have been made to SNEC in prototype form. These features include hybridisation with UTD, fast iterative solvers, MBPE amongst other features. When these extensions are formally incorporated into the SNEC program, then the theory behind the extension will be added to this manual.
This sections details some of the computations that apply to cylinders.
The principal planes of the cylinder were
chosen such that 
is tangent to the
cylinder in the XY plane and 
is in the direction of
the z-axis of the cylinder. The radius of curvature in the XY plane for an
elliptical cylinder is given by
|
|
(1) |
The plane of incidence is defined as the
plane containing 
.In general the radius of curvature in a plane at an angle 
from the principal
surface axes is given by Euler’s theorem as :
|
|
(2) |
For the cylinder, 
is as given in section
2.1, whilst 
. The angle is computed as :
|
|
(3) |
This details how to find the distance along
the surface of the cylinder from elliptical angle 
to 
in a given direction.
The arc length is given by :
|
|
(4) |
where
is the elevation angle
of the path traversed between and .
The transition function used in both the UTD edge and curved surface diffraction is defined by [ 1]:
|
|
(5) |
For large argument
|
|
(6) |
For small argument
|
|
(7) |
For argument 
, the interpolation scheme used for numerical computation is
:
|
|
(8) |
where the values for the iterative scheme are obtained from :
|
|
|
|
||
|
|
Real |
Imaginary |
Real |
Imaginary |
|
0.3 |
0.0 |
0.0 |
0.5729 |
0.2677 |
|
0.5 |
0.5195 |
0.0025 |
0.6768 |
0.2682 |
|
0.7 |
||||
