Analysis and possible mitigation of interferences between present and next-generation marine radars

The maritime traffic is significantly increasing in the recent decades due to its advantageous features related to costs, delivery rate and environmental compatibility. For this reasons it requires a high degree of control and an adequate assistance to the navigation. The related systems are the Vessel Traffic System (VTS), mainly using radar and the Automatic Identification System (AIS). In the recent years a new generation of marine radars with a lower cost of maintenance is being developed. They are based on the solid-state transmitter technology and uses coded "long pulse" in transmission, i.e. high "duty-cycle", with "pulse compression" in reception. The main drawbacks of these apparatuses are the interference effects that they might cause on existing marine radars, becoming critical when the traffic density increases. The AIS data (identity, location, intention and so on) can be useful to estimate the mutual distances among ships and the mean number of surroundings vessels, that is the number of marine radars in visibility. Using suitable models it is shown that the high duty-cycle of solid-state marine radars can generate severe interference to all marine radar sets in visibility with a significant reduction, well below the international regulations, of their detection capability. The mitigation of these damaging effects, not an easy task, can be achieved by changing the radar waveforms, i.e. resorting to Noise Radar Technology.