Indirect Ionospheric Spread-Doppler Clutter in High-Frequency Surface-Wave Radar

High-frequency surface-wave radar performance is sometimes compromised by spread-Doppler clutter generated by scattering interaction between the radar, the ocean surface and the Earth's ionosphere. In the paper, we show, using computational electromagnetic modelling, a previously unidentified scattering path as a potential spread-Doppler clutter source. This path is when the radar-transmitted signal is scattered from the ocean surface to the ionosphere and back to the ocean surface and then propagates to the radar receiver. This newly identified path has the same elevation of departure and elevation of arrival as surface-wave targets, greatly complicating spread-Doppler clutter mitigation.