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Risk Reduction - Quantified Performance - Cost Benefits

Installed Performance Prediction - risk reduction by calculating propagation, system, environmental and platform losses for rf systems

Installed Performance Prediction - What Is It?

With any Radio Frequency (RF) installation, all aspects of that system can be tested to ensure that they meet their individual design specification.

However, this does not guarantee that when the equipment is fitted together and installed, that the installation will work as expected. Moreover, potential problems are exacerbated by one or both ends of the RF system being fitted to a mobile platform.

Only by specifically addressing the installed performance can potential problems be anticipated and the required performance be demonstrated.

Mathematical modelling can evaluate the degree to which RF transmitters and receivers can communicate with each other. It can highlight system limitations, quantify expected performance and aid in recommending improvements.

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Types of RF Systems

FanField has developed and used installed performance models to predict virtually all types of RF system. These include:

  • Weapon systems
  • Radar
  • Communication links
  • Navigation aids
  • Avionics
  • Broadcast
E3D - Airborne Early Warning

RF systems can be fitted to fixed or mobile ground platforms, aircraft, ships or satellites. Any or all of these links can be analysed using installed performance modelling.

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Cost Benefits

There are many benefits associated with modelling and installed performance predictions - not least those associated with minimising costs.

The cost of modifications to an installed system rises as the development and production programme progresses.

Modelling can quantify and guarantee installed performance early in the procurement cycle thus saving development, installation and retro-fitting costs.

Performance proving trials are very expensive to conduct and are limited to incomplete performance evaluation. Modelling can highlight potential problem areas and recommend changes to proposed trials plans thus making trials more cost effective. For example, by modelling prior to its occurrence, we were able to show that a particular proposed trial would not have exposed any installed performance shortcomings, as the problem aspect angles were not being assessed.

Trials can also be used to validate existing models. If such a validated model is used, a higher degree of confidence can be placed in the expected installed performance, even if the number of trials is considerably reduced.

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Further Benefits

Quantifying expected installed performance has many benefits. Existing systems can be analysed and any limitations examined. Changes in procedures and system operation can sometimes overcome limitations resulting in more effective system performance.

The effects of hostile environments can only be assessed by modelling.

There is a danger that new systems can be over designed to ensure adequate performance. This can result in more expensive and possibly more unreliable equipment. Modelling can eliminate this risk and ensure that equipment meets its requirements.

Modelling can answer many what if questions relating to system performance. If new concepts require investigation or if modifications to existing systems are proposed, the benefits can be quantified by modelling prior to the cutting of metal.

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Types of Predictions

FanField has developed numerous installed performance models of RF systems. Some of these have included delivery and support of the software in order that our Clients can perform their own what if assessments. Alternatively, FanField offers a complete service and produces reports on predictions of installed performance. Such predictions can include the following:

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Polar plot output - showing installed performance variation with aspect angle of the platform

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Power distribution of RF link - showing the statistical variation of the link

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Pie chart of degradation factors - defining the effect of individual aspects on the overall installed performance

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3-d charts of probability of successful link - for example, probability against both range and azimuth aspect angle

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Effect of variation of system parameters - for example, sensitivity of system performance with transmitter power

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Comparison of predictions with specific measurements or other models

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Computer demonstration of the changes with time in installed performance for a dynamic platform

Whatever your requirement, FanField will work with you to produce the solutions to your specific problem.

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Modelling Techniques

FanField applies a variety of techniques to installed performance modelling problems. These techniques consist of the following, or combinations of the following:

Statistical: This uses analytical processes to give a precise statistical result.

Deterministic: This denotes a process, the resulting effect of which is entirely determined by the inputs and initial state.

Monte Carlo: This generally applies to the introduction of random variables into a predictable (statistical or deterministic) simulation. Many runs of a Monte Carlo simulation will give a meaningful statistical result.

Whatever your requirement, FanField will work with you to produce the solutions to your specific problem.

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Aspects Included in Installed Performance Modelling

RF Power Budget

The RF power budget is fundamental to the installed performance of RF systems.

FanField usually makes use of PatternMaster to accurately predict the installed antenna pattern, taking into account any structure close to the antenna. Full 3D patterns can then be used in the performance predictions.

System parameters such as transmitter power, receiver sensitivity and all losses, are required for the model. These can consist of specified values or a spread of typical or measured data can be included in the statistical analysis.

If one end of the RF link is a mobile platform, then the manoeuvre characteristics of the platform should be analysed. They can be included as a time stepping track, giving position and attitude of the platform or can be modelled as a statistical distribution. There are benefits associated with both methods.

In certain circumstances the effect of multipath from ground or sea can severely affect installed performance and is therefore another significant factor in the RF power budget analysis.

The physical characteristics of the land surrounding ground based antennas affect the propagation and can be included in the analysis.

For radar and similar RF systems, clutter may also be important.

System Aspects

When modelling a specific RF system there will always be some aspects that are unique to that system. An example is the Global Positioning System (GPS). Unlike most other RF systems, details of the positions of the GPS satellites are required for installed performance predictions to be made.

Equipment Reliability

Any system is only as good as it is reliable. The system's reliability can be modelled.

If the mean time between failures of the system components is known, then its expected operation can be determined. Some items of equipment, such as transmitters, are expected to degrade over its operational life. Other equipment, such as a phased array antenna consisting of many elements, can operate with only a slight degradation in performance even when one part of that equipment fails. The effect of all these aspects on installed performance can be modelled.

Operator Effects

How operators use the RF system can be important, particularly for older systems which have a higher degree of manual input. Operator effects are difficult to simulate as there can be variation between people. However, these effects can be quantified by estimates or measurements for inclusion in the modelling.

Timing Considerations

All RF systems will have some timing aspects relating to them. They can be divided into two types - correlated and uncorrelated. For example, glint, which affects a target's Radar Echoing Area (REA), is uncorrelated over a timing interval of 1ms, which corresponds to the typical time between radar pulses. On the other hand, a platform can normally be considered stationary over the same time frame.

Therefore, the models must consider the time frame that is important for the system. For a communication link, the important time frames are the lengths of the message bits and the overall message length which constitute the transmitted RF signal.

Interference Effects

Interference from other emitters can sometimes only be considered by modelling, as the effect of many interfering sources cannot easily be included in a trial.

Modelling can include the effect of interference from similar systems to the one being considered. Other interfering sources can be friendly systems operating on the same frequency band. Furthermore, enemy emissions, such as jamming, can be easily modelled.

A multiple emitter environment can be analysed for electromagnetic compatibility (EMC) considerations.  The resultant field strength can be determined for a volume of space and all desired frequencies.

FanField's installed performance modelling can include analysis of many different aspects. The degree to which they are implemented is matched to our Clients' requirements.

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Validation

Comparison of Predicted Signal to Noise

Validation of any mathematical model is extremely important. FanField has developed a distinguished reputation for high quality software in the specialised field of installed performance modelling of RF systems. Our models have been extensively validated against equipment specifications, results from trials and measurements as well as independent models developed in the UK and in other NATO countries.

Consequently, our clients can be assured that a high degree of confidence can be placed in the predictions from FanField's installed performance models.

FanField is accredited to BS EN ISO 9001 with ISO 9000-3 (Software). Therefore all software is fully documented, tested and validated.

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Preferred Solution

Different types of installed performance models, producing various predictions can be performed by FanField.

The aspects to be included in the installed performance models are individually tailored to our Clients' needs, as are the modelling techniques incorporated in the software.

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FanField Ltd., Oxley House Cottage, Oxley Hill, Tolleshunt d'Arcy, Maldon, Essex, CM9 8EN
Tel: 01621 810095 Fax: 01621 810095
e-mail:
sales@fanfield.co.uk