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Abstract

For some time the Glaciology section of the Australian Antarctic Division has
operated a land-based radar to measure the depth of glacial ice in Antarctica. The
radar was mounted on a sled and towed around the Lambert glacier by bulldozer at
5km per hour. High power radio frequency pulses are transmitted down into the
glacial ice, propagate through the ice and reflect off the bedrock below. The
reflected pulses are picked up by a receiver, amplified and passed on to a signal
processing section. The waveforms from the signal processing section are logged
and displayed. The time taken from pulse transmission to detection, which is
proportional to ice depth, may then be obtained. Signal averaging capabilities were
required to improve the system signal to noise ratio and enable ice depths of over
3km to be observed. The ground based display and logging system used a digital
oscilloscope with signal averaging capabilities to digitise and process incoming
radar return echoes. Up to 256 radar return echo waveforms were averaged, the
result being displayed and downloaded to an IBM PC via an 1EEE488 link. Future
ice depth measurements will involve airborne operations increasing the travelling
speed from 5km per hour to 180km per hour. This speed increase will require
greater data rates of the display, and logging system In addition the airborne
antenna, being carried by a helicopter, is physically smaller than the antenna
mounted on the 60 tonne overland system. A smaller antenna leads to smaller
antenna effective area, which in turn reduces the radar range. The high-speed digital
signal processor (DSP) and high-speed analogue to digital converter (A to D) circuit
board forms part of the ice radar display and logging system, replacing the slower
digital oscilloscope system. The DSP will have sufficient speed to keep pace with
the data rates required for airborne operation and provide improved signal
processing power to compensate for reduced radar antenna gain.
As no suitable 'off the shelf' product was found the new system would utilise a
custom designed high-speed DSP and high-speed A to D converter electronic circuit
board. This document concerns the design of a high-speed DSP and A to D circuit
board for an ice radar application.

Item Type:	Thesis - Unspecified
Authors/Creators:	Brocklesby, Andrew K.(Andrew Kenneth)
Keywords:	Ice sheets, Radar
Copyright Holders:	The Author
Copyright Information:	Copyright 1999 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).
Additional Information:	Thesis (M.Eng.Sc.)--University of Tasmania, 1999. Includes bibliographical references
Item Statistics:	View statistics for this item

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