an efficient propagation simulator for high frequency signals and results from hf radar experiment

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

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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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Lower path – Extraordinary waveRight-hand circular

polarisation

Upper path – Ordinary wave

Left-hand circular polarisation

Polarization Fading Model

Faraday rotation due to O and X wave interference

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Polarization Fading Model

Perturbation techniques to ascertain the change in phase path due to irregularities

dgdsPdunperturbedunperturbe

Use of frequency offset method to take into account of the magnetic field

Hxo fff cos2

1,

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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):

0),(2 22

Utgkt

U

g

Ukj oo

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

Dual-polarization receiver in Darwin

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Experimental Results

Finding the signal component along each sweep

FMCW Radar signal

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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:

)),(cos(),( tftfAVH )),(sin(),( tftfAkVV A - amplitude component

- phase component Therefore:

H

V

Vk

Vtan )tan1( 222 HVA

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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 single-mode 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