Transcript Slide 1
An Efficient Propagation
Simulator for High Frequency
Signals
And Results from HF radar experiment
Kin Shing Bobby Yau
Supervisors: Dr. Chris Coleman & Dr. Bruce Davis
School of Electrical and Electronic Engineering
The University of Adelaide, Australia
Overview
HF Ionospheric Propagation Simulator
Simulation results
Comparisons with Experimental Results
Discussions
Conclusions
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Introduction
HF radio system is still prevalent
Military Over-the-Horizon RADAR
HF communications
Commercial broadcasting
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Ionospheric Propagation
Simulator
A need for wideband HF propagation
simulator
Focussing on the fading effects of HF
signals
Employ theoretical model of fading
Efficient algorithm based on analytical expressions
Two components of fading model:
Polarization Fading Model
Amplitude Fading Model
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Polarization Fading Model
Faraday rotation due to O and X wave
interference
Upper path –
Ordinary wave
Left-hand circular
polarisation
Lower path –
Extraordinary wave
Right-hand circular
polarisation
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Polarization Fading Model
Perturbation techniques to ascertain the
change in phase path due to
irregularities
ds dg
P
unperturbe d
unperturbe d
Use of frequency offset method to take
into account of the magnetic field
f o, x
1
f cos f H
2
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Amplitude Fading Model
Focussing and defocussing of radio
waves due to movement of large scale
ionospheric structure
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Amplitude Fading Model
Parabolic approximation to Maxwell’s
equation (Wagen and Yeh):
U U
2 j ko
2 ko2 ( g , t )U 0
g t
U is the complex amplitude, is the
refractive index with irregularities
g and t are the local longitudinal and
transverse coordinates
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Amplitude Fading Model
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Simulator Implementation
Numerical ray
tracing is used for
the path quantities
Accurate ray
homing for finding
all possible paths
(Strangeways,
2000)
Fading is
calculated by the
fading models
Ionospheric condition
information
Simulation parameters
Ray Tracing Engine
(RTE)
Polarisation Fading Model
(PFM)
Amplitude Fading Model
(AFM)
Ionospheric Propagation Simulator
(IPS)
Data Display Module
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Simulation Results
Alice Springs to Darwin
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Simulation Results
10.6MHz - = 0.05, L = 350km, v = 200m/s
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Simulation Results
10.6MHz - = 0.05, L = 350km, v = 200m/s
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Simulation Results
10.6MHz - = 0.05, L = 350km, v = 200m/s
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Simulation Results
10.6MHz - = 0.20, L = 350km, v = 200m/s
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Simulation Results
10.6MHz - = 0.20, L = 350km, v = 200m/s
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Simulation Results
10.6MHz - = 0.20, L = 350km, v = 200m/s
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Comparison – Experimental
Results
Signals from
Jindalee
Radar
transmitter in
Alice Springs
Dualpolarization
receiver in
Darwin
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Experimental Results
FMCW Radar signal
Finding the signal
component along
each sweep
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Experimental Results
6:30PM local time – Spectrograms
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Experimental Results
6:30PM local time – Time fading
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Experimental Results
6:30PM local time – Frequency fading
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Experimental Results
7:30PM local time – Spectrograms
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Experimental Results
7:30PM local time – Time fading
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Experimental Results
7:30PM local time – Frequency fading
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Fading Separation
Separate amplitude and polarisation fading
Two orthogonal antennas:
VH A( f , t ) cos( ( f , t ))
VV k A( f , t ) sin( ( f , t ))
A - amplitude component
- phase component
Therefore:
VV
tan
A2 VH2 (1 tan2 )
kVH
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Fading Separation
7:30PM local time – Time fading revisited
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Fading Separation
7:30PM local time – Time fading separation
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Fading Separation
6:30PM local time – Time fading revisited
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Fading Separation
6:30PM local time – Time fading separation
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Fading Separation
Fading separation works well for singlemode case
For multi-mode propagation:
Exploit FMCW radar signals
Separating the modes using Range-gating
techniques
Applying fade separation to each of the modes
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Discussion
Further analyzing with experimental data
Comparisons with ionosonde data
Discover the structure of the ionosphere during
the period of rapid fading
Simulating propagation under realistic
irregularity strctures
Possible applications:
Real-Time channel evaluation
Test-bed for fading mitigation techniques
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Conclusion
Efficient Ionospheric Propagation Simulator
has been developed
Experiment to observe fading of HF signals
was done successfully
Comparisons between experiment and
simulation are promising, especially for
single-path polarization fading
More work to be done on the experimental
data
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Acknowledgements
Defence Science and Technology
Organisation (DSTO)
Dr. Manuel Cevira
Dr. Chris Coleman
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