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Paper for the Conference "Millenium 2000 Antennas and propagation" Davos/Switzerland, April 2000 for system simulations
Dr.-Ing. Gerhard Greving
NAVCOM Consult
Bahnhofstr. 4
D-71672 Marbach
navcom.consult@t-online.de
Introduction
The effects of objects/buildings
and of the ground on radio systems (radio navigation (so-called navaids),
landing and radar systems) have to be analyzed in advance before installing
the system or before constructing the object. This kind of technical problems
arises more and more on airports and en-route due to the drastically increasing
air traffic which affects the mentioned systems. Also, more and more large
and high buildings and objects are constructed close to the airports and
close to the navigational and radar systems. These can be e.g.
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real buildings like hangars, terminals
on airports
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singular or assemblies of cranes for
the construction of buildings
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aircraft in the radiation field
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power generating windmills or high voltage
lines in the countryside close to navigational or radar systems
Also, some systems depend on the ground
properties in the radiation field and the ground characteristics has to
be taken into account adequately, like the so-called "humped runways" or
the wet or dry snow layers on top of the ground.
The navigational and radar systems
in question are e.g.
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landing systems like the Instrument
Landing System ILS (110MHz) and the Microwave Landing System MLS (5GHz)
; GPS in future (1.2/1.5GHz)
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radio navigational systems like the
VOR/DVOR (110MHz), DME/TACAN systems (1GHz)
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the primary and secondary radar (ASR,
SSR) (1GHz, 2.7GHz).
The pre-analysis of the system performance
under the effect of the mentioned objects is a "system simulation" problem
where a number of subtasks have to be solved and have to be integrated,
namely the antenna problem, the wave propagation, transmitter/receiver
problem, signal processing (Fig. 1). In any case the decisive "system
parameter" has to be primarily the final result of the simulation
under the realistic system environment. This system parameter (e.g. bearing
angle and its tolerances, range error; existence of ghost tracks in the
radar case) has to be deduced uniquely from the field quantities. The field
quantities may constitute a side result in the best case, e.g. fieldstrength
in certain regions or points as the system coverage parameters. However,
in the context of this conference mainly the antenna and wave propagation
part and its related numerical methods are discussed.
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