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The different methods cannot be explained
in greater detail here. The reader is referred to the applicable textbooks
and publications.
The methods available when applied
to the above mentioned objects have to comply with the criteria of giving
valid results, in general the particular wavelength ratio to the size of
the object. It turns out that all methods which are rigorous (e.g. MoM,
FE,FD,FI), cannot solve the problem due to the extreme computer storage
and computer time requirements. The most suitable methods are the ray method
(GTD/UTD) for general cases and the current integration method (PO) for
simpler cases. However, these are approximate methods and this application
has to be controlled very carefully within the range of the approximation
and its applicability, even though numbers and curves are generated. If
not applied correctly, wrong results may be achieved.
The most capable numerical realizations
(tools, computer programs) are relatively difficult to handle and require
personnel with a high level of engineering know-how on
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Antennas (antenna characteristics, radiators,
arrays, polarisation, tolerances)
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RF-technology (receivers, transmitters)
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Wave propagation
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Numerical techniques
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System know-how and experience with
the system to be analyzed.
If these numerical analysis tools in
general and in particular in a simplified and approximate version, are
distributed for public use some conditions should be met strictly. A detailed
manual should be available for the user explaining in detail the
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theory and approximations implied
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applicability and limits for different
objects and ground
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expected range of accuracy.
In any case, the user should be trained
adequately before applying the numerical methods being aware of the above
mentioned conditions and assumptions. The user must be able to identify
and interprete numerical artefacts uniquely for the applied method, e.g.
the mentioned discontinuities for the GTD/UTD-method.
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