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SuperNEC Newsletter – Feb 2005 |
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· Australian Navy Patrol boat simulated using SuperNEC · Assembly competition |
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In 1993 CEA Technologies won a contract to provide the communications
system for a new fleet of Patrol Boats for the Australian Navy. Supernec
was used extensively during the development phases of this project
as both a design and analysis tool. 1. Introduction The antennas used on the boat were either systems
that CEA had designed previously or units bought of the shelf. The
main aim of the design phase was to work out the best locations for
all of the antennas with consideration of system priority, interference,
radiation hazard and coverage. This
proved to a challenge given the small size of the platform, the number
and variety of systems used and the radiated power levels required.
The systems range from HF Transmit through to L band satellite services.
The first vessel of 14 vessels entered the water
in January 2005 and has commenced harbour
trials. Some recent pictures are shown below. The vessels are built
by AUSTAL in 2. Scope This
document provides a snapshot of the simulations carried out using
Supernec. Examples of Radhaz,
Interference and coverage are provided with pictures of the models
and some of the plots obtained. 3. Radiation Hazard The
example given is of the HF transmit radiation. There are two high
power HF systems that use canted 10 meter whips mounted forward of
the bridge on opposite sides of the deck. The model used is a wire
grid style. The purpose of the simulations was assist in the placement
of the whips by examining the extent of the radiation hazard regions. Figure 1 Wire Grid Model . Figure 2
Field at Figure 3 Near field at 2 MHz, HF
transmit 4. Simultaneous
Operations One requirement on the RPB is that the HF transmit
and HF receive operate simultaneously. A field analysis was carried
out to determine the best locations for the HF receive antennas (actives)
to meet this requirement. The plot shown below shows the electric
field due to one of the HF transmitters. By examining the strength
of the field at various locations using this type of plot suitable
positions for the active HF receive antennas were found. 5. Coverage Some antenna coverage examples are provided below,
they are for one HF whip and a selection of VHF and UHF systems. 5.1 HF System A wire grid model was used of the boat. Note the
affect the mast structures have on the radiation pattern at the frequency
simulated. The forward and aft masts act as directors or reflectors
depending on the frequency in use. Figure 4 3-D Coverage Plot for HF Transmit Figure 5 HF Transmit Azimuth Patterns at Horizon
for Various Frequencies 5.2 Coverage
for VHF AERO, VHF IMMB, UHF CIVIL and UHF MIL Line of Sight. A plate and wire grid model was used for in the
simulation. Antennas are wire models and the boat used UTD plates. Only those parts of the vessel which impacted
the patterns at these frequencies where included in the model. UTD
interactions were set to account for reflections and diffraction from
the mast surfaces. The UTD model was used because of the large electrical
size of the structure. The mix of wire structures for the antenna
and UTD for the vessel worked well. Figure 6 Model Used for VHF and UHF Simulation Figure 7 VHF AERO for various frequencies Azimuth plots at theta =88 deg Figure 8 UHF Civil for various freqs, Azimuth plots at theta=88 deg Figure
9 UHF MIL LOS 3D Plot Figure
10 UHF MIL LOS Elevation Plot Figure 11 UHF MIL LOS Azimuth Plot for various elevation angles |
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Q: I am writing SuperNEC under
Windows XP but the SuperNEC interface does
not display correctly. How can I fix this? A: The version of MATLAB being used was released before
Windows XP. The problem can be solved by either upgrading your versions
of MATLAB or setting your windows display to classic mode.
Q: Do you sell complex grid structures such as aircraft
structures? A: We have a number of wire grid models available. These
include the C-130, HAWK, Puma, Boeing and
Q: I need to manipulate some of the simulated data in
SuperNEC. How do I do this? A: To manipulate simulated data in SuperNEC, select the data set, such as Excitation under Parameters vs Frequency and click on the
workspace button. This will put the data to the MATLAB workspace to
be manipulated and plotted as required. |
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A
unique feature of SuperNEC is the use of
assemblies to simplify the modeling process for the user. Assemblies
are pre-defined (or user defined) antennas or structures that can
be re-used when modeling communication systems. In your current version
of SuperNEC you will find a wide variety
of assemblies including yagi’s, helices,
spheres, dipoles, LPDA’s and many others.
In
2005 we would like to encourage our users to create their own assemblies
using SuperNEC. The best ones will be added
to the next version of SuperNEC where all
users can benefit. If
you have never written an assembly in SuperNEC
please keep in mind that you need MATLAB to write an assembly. Please
have a look at the Input URM (User Reference Manual) under section
1.12 “Writing your own assemblies” for assistance
in doing this. (The manuals can be found in the Help Menu of SuperNEC). Please
e-mail the assembly (*.m file) to support@poynting.co.za with the subject Assembly
Competition. We will publish the best assembly that we received, in
our next newsletter and send the winner an AMAZON gift voucher of
USD 50.00. At the
end of the year we will select the best assembly of 2005. This person
will receive a full SuperNEC license for
one year worth USD 5340. |
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Modern technology not only brings along the freedom
to communicate with whom you want, when you want, and ease of use,
but very often also its technical problems as well. Cell phones are indispensable - but only if
you are able to use them. Nobody
escaped the very often “dropped calls”, bad signals and low voice
quality during that all important emergency, business or private phone
call. Poynting
Antennas (www.poynting.co.za)
has developed various special GSM cell phone “range extender” antennas
to help you overcome those typical “low signal” problems. You need
a full-scale signal for operating GPRS, MMS or if you want to gain
web access via your cell phone. The
company offers a complete range of antennas that will allow you to
experience good solid cellular communications – isn’t that what cellular
communications is intended to provide? This LPDA the first of a new range of robust,
compact, high performance Cellular high gain antennas designed specifically
for end users battling with bad reception in remote areas and for
business applications, such as least cost router (LCR) systems and
cellular payphone installations. The
product features new advances in manufacture and design which translate
to real benefits for the user. Wide band operation over the entire
Cellular band, including full GSM, 3G, and other global cellular standards
means that the antenna can be used anywhere in the world for any type
of Cellular installation. High gain (at least 11dBi) operation and
excellent matching (VSWR lower than 2:1) over the entire band ensures
that irrespective of which network the user is connected to, this
antenna will always work as promised, delivering at least 16 times
the power of most cellular handset antennas. More power equals longer
battery life, better signal quality, fewer dropped calls and more
money saved. The
antenna addresses the growing least cost router market by allowing
even more cellular devices to be connected to a single antenna via
our comprehensive cellular splitter range. Multitudes of badly interacting
unreliable stub antennas connected to filing cabinets and door frames
are a thing of the past! Its high gain directionality also reduces
the effects of multi-path interference, making LCR installation much
more reliable and consistent. The
CellLPDA range is manufactured using light-weight
aluminium and hardy polycarbonate plastic, making it compact,
strong and light for more cost effective shipping, easier installation
and a hugely extended lifetime, even under the harshest conditions
of UV and weathering. It is fully operationally rain and weather proof. Please
contact sales@poynting.co.za
or 0800 443 443 should you want more information or a quotation.
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