July 2004 Newsletter

SuperNEC Newsletter - July 2004

Simulation of UAV using SuperNEC

Study Guide for Electromagnetics and Antennas

Frequently Asked Questions (FAQ)

2 - 3 GHz Grid Dish Antenna

Simulation of UAV

Poynting Innovations was contracted by Denel Aerospace Systems to do a study on their Unmanned Aerial Vehicle (UAV). As part of the project the technology was transferred to their client in conjunction with SuperNEC training.

A number of antennas are used for communication on the UAV seeker. The performance of these antennas may be influenced by the structure of the UAV as well as by the antennas' proximity to one another.
As a first exercise Poynting engineers did RF measurements on samples of the material that was used in the UAV. Experience has shown that suppliers of composite materials such as carbon fibre, glass fibre, etc. can very seldom provide electrical material property information for higher frequencies. A material analysis for higher frequencies was therefore done on the carbon fibre, glass fibre and honeycomb glass fibre that is used in the UAV. The results of this study were used to predict the influence of the materials on the antenna's performance. The low frequency numerical model of the UAV was constructed using Method-of-Moment wire segments. A high frequency model was constructed using UTD plates and is a representation of the entire surface of the UAV. A 20:1 and 4:1 copperscale model was constructed to validate the low frequency and high frequency numerical models respectively. The comparisons between simulated and measured results on the copper scale models showed a typical pattern deviation of 2 dB for the low frequency model and 3 dB for the high frequency model.

During this project training was provided on the analysis and evaluation of the currently installed antennas of the UAV. The validated numerical models were used to simulate the performance of the directional antenna, omni directional antenna and two monopoles in SuperNEC. These simulated results were then used to evaluate the signal strength between the base station and UAV over a number of flight profiles using ASEP (Antenna Simulation and Evaluation Package).

From the analysis of the antennas mounted on the UAV airframe and the ASEP simulations, the following points could be deduced:
- The nose section or canopy has the greatest effect on the antennas' radiation pattern introducing nulls of up to - 25 dB.
- The tail section does not have a significant effect on the antenna radiation patterns
- The antennas on the UAV do not influence the radiation pattern of one
another significantly

ASEP shows that distance plays a significant role in reducing signal strength along with nulls introduced by the UAV airframe.
It was suggested that the antennas be mounted underneath the UAV to reduce the effect of the airframe on the radiation pattern. This is especially significant when the UAV is close to the base station or when banking.
Once established and qualified, the electromagnetic model provides a cost effective tool to determine the optimal placement of antennas on an airframe and to aid with the evaluation of antenna performance when antennas are added or moved. In addition, the Radar Cross Section of an airframe can be predicted with the same model, provided the model has been qualified over the required frequency range.

Study Guide for Electromagnetics and Antennas

A study guide for electromagnetics and antennas is now available from Poynting Software. The Study Guide for Electromagnetics and Antennas has been developed and written by Prof Alan Clark from the University of the Witwatersrand, in conjunction with Prof Andre Fourie and engineering students.
Prof Clark is an Associate Professor, lecturing third year Electromagnetics at the School of Electrical and Information Engineering. Prof Fourie lectures a fourth year Antenna course.
They have consulted widely in the industry, designed many antennas and associated electronic devices and have also published several papers.
This Study Guide consist of a 148 page, soft cover book, printed in full-color on high quality paper and a CD ROM with SuperNEC simulation software.
This book and CD set has arisen from the need to provide students with a "Virtual Laboratory" where they can perform EM and antenna experiments on the computer. SuperNEC allows the simulation of EM structures using MoM and GTD/UTD theory. SuperNEC also makes use of the excellent visualisation offered by MATLAB to display output as well as constructing and viewing input geometries.
The study guide provides some background theory on each topic, but its real value is in the tutorial like examples through which it leads the student. Starting in each case with some step-by-step SuperNEC examples, it also contains some open ended questions which can be examined with the aid of the SuperNEC simulator. SuperNEC allows for MATLAB Assemblies which predefines antennas or EM Structures using the m-file script language. Special assemblies were written to accompany the examples in the study guide and makes it easy for the student to investigate the EM/Antenna problem rather than spending time on the computer models.
Over the many years of teaching electromagnetics at an undergraduate level, lecturers have tried many forms of visualisation to get complex concepts across, but none is as effective as the use of SuperNEC.
Prof Clark believes that this book will be an aid to the student of electromagnetics: it is purposefully not pitched at any particular textbook of electromagnetics and it not meant to be one. Chapters include the following (Please note that this is not a comprehensive list):
- Transmission lines,
- Matching,
- Waves,
- Basic Antennas,
- Array Theory,
- Complex Antennas.
The SuperNEC EM Simulation Software includes student tutorials and animated help. The animated help was added in the latest version of SuperNEC and this allows the novice student to familiarise themselves with the software in a short period of time.
We think that students and lecturers will benefit greatly from this Teaching Aid.
We will be launching the SuperNEC Student Teaching Aid during a tour to the USA in June and would like to arrange a meeting with you should you find this of interest. We will be at:
- IEEE MTT-S Symposium in Fort Worth Texas from 8 - 10 June 2004
- 2004 IEEE APS Symposium in Monterey California from 20 -23 June 2004
An example from the Study Guide can be seen here. Please contact supernec@poynting.co.za for more info on this product.

Frequently Asked Questions

Q: I want to use the study guide and I am not a student. Can I do this?
A: Yes. Even though the student guide was developed with students in mind, it is ideal for anyone who wants to learn the basics of antennas or simulation.
Q: For which applications can SuperNEC be used?
A: Full 3-D wire antenna analysis and design.
Antenna placement studies on complex structures (e.g. like aircraft)
Genetic Algorythm optimisation.
A teaching aid or virtual laboratory.

Q: What is the difference between the trial SuperNEC Licenses?
A: There are 2 trial licenses:
Free Academic License:
Duration - 1 year
Limitation - 300 segments
Cost - Free
Requirements - You must be a student or lecturer and fax or e-mail proof (normally a University Card) to +27 11 262 5156.
You must have MATLAB v 6.0 or higher.
Demo License:
Duration - 30 days
Limitation - 300 segments
Cost - Free
Requirements - None. This demo license includes a MATLAB runtime License.

Q: What is the MATLAB runtime license and what does it have to do with SuperNEC?
A: The SuperNEC User Interface was written in MATLAB and therefore MATLAB is required to run SuperNEC. To accommodate users that do not have MATLAB we include a MATLAB runtime license at a nominal fee. Please remember that you can not write scrypt files to interface with SuperNEC if you have the MATLAB runtime license.

Q: What SuperNEC products can be purchased:
A: There are basically 4 SuperNEC products available:
- SuperNEC Lite (300 segments)
- SuperNEC (no limits)
- SuperNEC Parallel (for problems to large for single pc's)
- SuperNEC Study Guide (Teaching Aide with software limited to 500 segments)
There are different pricing structures for commercial and academic users. More info can be found here.

Q: What licensing options are available for SuperNEC products?
A: We can control access with a:
- Hardware Key (This is a dongle that you plug into the parallel port of the machine you want use SuperNEC on)
-Single PC license (This is a software file, supplied by us, that you have to copy onto the machine where you want to use SuperNEC on)
-Floating license (This is a software file, supplied by us, that you copy onto the server on the network. The number of people that can use SuperNEC simultaneously depends on the number of floating licenses that was bought. If 2 floating licenses were bought, a possible 10 users might have the software installed, but only 2 will be able to use it simultaneously.

2 - 3 GHz Grid Dish Antenna

Poynting is proud to announce a new grid dish antenna that covers the 2 - 3 GHz range. This forms part of their range of antennas for wireless applications.
This high gain, broad band, grid dish is ideal for the WLAN, WISP, MMDS bands and any other licensed band in the 2 - 3 GHz range. The gain of 22 dBi is higher than competitive products of the same size.
This robust antenna is galvanised and powder coated to make it corrosion resistant. It has a low wind resistance due to its design, which makes it ideal for high mast installations where wind loading is a problem.
The antenna is ideal for any point to point wireless application, but is especially suitable for use on light-duty masts and poles. The dish is supplied with a sturdy tilt, swivel bracket and hardware to mount it on a 50 mm pole and it is easy to install. Please contact our sales department at sales@poynting.co.za for more info or for a quotation for any of our products