Radio Frequency Interference Suppression Techniques
Klaus-Werner Gurgel and Thomas Schlick
University of Hamburg, Institute of Oceanography, Bundesstrasse 53, D-20146 Hamburg, Germany
Due to the world wide use of radio frequencies, HF radars need to share frequency bands
with other radio services. Especially in the MF (1 to 3 MHz) and HF bands (3 to 30 MHz),
there is a strong influence of the earth's ionosphere which attenuates and reflects the
radio signals. The ionoshere's conditions depend on the sun's radiation heating the different
layers of the ionoshpere during a day to night cycle. Depending on the day's time, strong
signals can be observed within the frequency band used by the HF radar which have been
reflected from all over the world.
This paper presents a number of techniques which can be applied to HF radar signal
processing to identify and reduce the impact of Radio Frequency Interference (RFI).
By scanning the frequency bands and selecting an optimal center frequency and bandwidth
prior to running a measurement cycle, the distortion of the measured results can strongly
be reduced. The remaining RFI varies with time and after identifying it's structure in the
HF radar backscatter spectra, most of it's impact can be removed.