Different Approaches of Signal Processing in HF-Radar Systems
Presented at the PIERS'96, Remote Sensing of Oceans, Paper 3
Klaus-Werner Gurgel and
University of Hamburg, Institute of Oceanography,
Tropolwitzstrasse 7, D-22529 Hamburg, Germany.
Tel: +49-40-42838-5742, Fax: +49-40-42838-5713,
HF radar systems use Bragg-backscattering of electromagnetic decameter waves
from the rough sea to measure surface current, wave height and
wave directional spectra. The systems can be operated at the shore or from
aboard of a ship. System characteristics, such as working range, resolution
and accuracy, mainly depends on radio frequency, antenna approach, sea state
and salinity of the water. Several appliances have been developed during the
last 20 years all over the world. In contrast to airborne or satellite
platforms, HF radar systems are ideal tools for monitoring ocean parameters
in coastal zones, due to their continuous operation.
The background behind this type of HF radar is to measure the amplitude and
doppler shift of the backscattered sea echoes. The algorithms to derive ocean
parameters from these doppler spectra have been described in several papers.
However, there exist different ways to process the radar echo to doppler
spectra at a specific range or azimutal angle. Range resolution can be acheaved
in time domain using short packages of electromagnetic waves at a constant
frequency (pulses) or in frequency domain using a continuously transmitted
linear frequency chirp. Azimutal resolution can be achieved by direction
finding or beam forming techniques. These different techniques and the required
steps in processing the backscattered sea echoes are described and the
advantages and disadvantages of the different approaches are discussed here.
It appears, that no system exists, that can be the ideal solution to all
possible applications, but for a given case, the best compromise can
be selected from the discussed approaches. Also further improvement in
technology, e.g. powerful chips for signal processing or frequency synthesis,
today allows more complex solutions.
This work has been funded by the European Commision DG XII within the MAST-2
programme, project SCAWVEX, ct94-0103.
last update 21-Jan-1998