|
|
 |
|
|
Ann. Geophys., 18, 1242-1247, 2000
www.ann-geophys.net/18/1242/2000/
© European Geosciences Union 2000
Ground clutter cancellation in incoherent radars: solutions for EISCAT Svalbard radar
T. Turunen1, J. Markkanen2, and A. P. van Eyken3
1EISCAT Scientific Association, SE-98123 Kiruna, Sweden
2EISCAT Scientific Association, FIN-99600 Sodankylä, Finland
3EISCAT Scientific Association, N-9171 Longyearbyen, Norway
Abstract. Incoherent scatter radars measure ionosphere
parameters using modified Thomson scatter from free electrons in the target (see
e.g. Hagfors, 1997). The integrated cross section of the ionospheric scatterers
is extremely small and the measurements can easily be disturbed by signals
returned by unwanted targets. Ground clutter signals, entering via the antenna
side lobes, can render measurements at the nearest target ranges totally
impossible. The EISCAT Svalbard Radar (ESR), which started measurements in 1996,
suffers from severe ground clutter and the ionosphere cannot be measured in any
simple manner at ranges less than about 120–150 km, depending on the modulation
employed. If the target and clutter signals have different, and clearly
identifiable, properties then, in principle, there are always ways to eliminate
the clutter. In incoherent scatter measurements, differences in the coherence
times of the wanted and unwanted signals can be used for clutter cancellation.
The clutter cancellation must be applied to all modulations, usually alternating
codes in modern experiments, used for shorter ranges. Excellent results have
been obtained at the ESR using a simple pulse-to-pulse clutter subtraction
method, but there are also other possibilities.
Key words: Radio science (ionospheric physics; signal
processing; instruments and techniques)
Full Article in PDF (314 KB) |
|
|
