|
|
|||
|
SuperNEC Newsletter - Dec 2004 · HAWK 100 simulated using SuperNEC |
|||
|
|
|||
|
|
|||
|
Poynting was approached by Chelton
Avionics to evaluate VHF/UHF (30-420 MHz) communication on the HAWK
Lead in Fighter Trainer (LIFT).
Azimuth pattern comparison Roll pattern comparison
|
|||
|
|
|||
|
|
|||
|
Q: Does Poynting Software offer SuperNEC Training
Courses? A: Yes, Poynting Software does offer training courses for SuperNEC. This consists of a 4 day course that takes the
user form basic concepts to advanced modelling. Courses can be offered
at our premises or at yours as you prefer. Q: How can I optimise an antenna design in SuperNEC? A: SuperNEC has a genetic algorithm optimiser
that can be used to optimise multiple parameter antennas with respect
to gain and VSWR over frequency. Q: i want to create a complex structure like
an aircraft or vehicle, how do I do this? A: The program SIG (Structure Interpolation and Gridding)
is used for this purpose. A detailed example is contained in the SIG
GUI help files. Q: Do I have to interface with SuperNEC through
the GUI? A: SuperNEC
can be accessed fully through a command line interface in MATLAB.
This enables the user to write their own programs and interface to
SuperNEC. |
|||
|
|
|||
|
Tunnel and |
|||
|
|
|||
|
|
|||
|
|
|||
|
|
|||
|
Modelling an array of modified Yagi antennas using SuperNEC The starting point
for this tutorial is the Yagi antenna. SuperNEC has a number of built-in antennas that can be very
easily constructed. To add a Yagi antenna
to the structure, select the menu item Add | Assembly | antennas |
snyagi. A dialog box requesting
the parameters of the Yagi will appear.
The main parameters
of the Yagi are the element spacing, element
lengths and the radii of the wires making up the Yagi.
The above dialog shows the default settings for a Yagi,
which is a Yagi with 5 elements each spaced
0.2 m apart. On pushing the OK button, a segmented Yagi
will appear in the structure editor.
On the bottom left
hand side of the structure editor window is the text ‘Model Freq :’.
The number to the right of this text specifies the frequency at which
the structure is modelled. In this case, it is set to 300 MHz.
You can change this figure to generate a model of the antenna at a
different frequency. Try changing the number to 400 and then push
the ‘Set’ button. Note that the number of segments used to model the
antenna increases. Let us now assume
that we want to connect the centre of the last two elements of the
Yagi with a 45 W transmission line. This is achieved as follows :
1.
Set the group level to ‘low’
so that we are able to select individual segments.
2.
Left click on the centre
segment of the last element of the Yagi
(this should highlight the segment in red).
3.
Hold the shift key down
and left click on the centre segment of the second last element of
the Yagi (you should now have two segments highlighted in red
as shown below).
4.
Select the menu item Add
| Primitive | Network | Transmission Line
5.
The transmission line dialog
box will appear.
6.
Push the OK button and another
dialog asking how the segments should be linked will be displayed.
7.
Push the ‘Pairs’ button
and the transmission line will be added to the structure. We will now put a lumped element load of 3 W
onto the tips of reflector element. This is achieved as follows :
1.
Select the two segments
as shown below:
2.
Call the menu item Add |
Primitive | Load.
3.
Fill in the parameters of
the load. Note that the SuperNEC symbol for a load is a black mark. You can check the
loading of parameters of each of the segments by double clicking on
the loaded segments.
We will now create a stacked array of these Yagi’s.
The stack will be vertically oriented and the spacing between antennas
will be 0.5 m. To do this :
The structure will
now be reflected along the x-axis (y-z plane). To do this :
Note that the reflected
portion of the structure is grey. This grey colour means that these
elements of the structure form an image of the original structure
and that symmetry will be used in the simulation. If you modify the
structure (other than to add transmission lines and excitations),
then the symmetry of the model will be lost. |
