Ship detection by maritime and coastal surveillance radars ? Signals and processing

Radar applications for maritime and coastal surveillance are numerous. First and foremost, there is the detection and localization function, and sometimes a ship classification function based on the radar signature. This second section is dedicated to the detection function, the basic function of surveillance.

The specific features of radars for maritime and coastal surveillance are mainly: the targets of interest and the environment in which these targets are perceived. Targets of interest are different types of craft or ships. Their main characteristic, as seen from a radar, is the SER (Radar Equivalent Surface). After a precise definition of the concept of SER, the article outlines the physical mechanisms contributing to its mean value and fluctuation modes, including phenomena specific to marine targets, such as sea reflection and wave masking. It also indicates:

• general principles of SER calculation for marine targets ;

• their usual values for different types of vessels;

• the main fluctuation models used.

The specific environment for maritime surveillance radars is sea clutter. The main characteristics of sea clutter influencing performance and design choices are :

• the mean sea reflectivity level σ ₀ ;

• the statistical characteristics of the clutter signal ;

• the characteristics of its Doppler spectrum.

The physical phenomena influencing these characteristics are presented, along with models for predicting their values, depending on the observation context and the characteristics of the radar architecture. The various mechanisms involved in the detection process are then described. The notions of :

• optimal detection ;

• suitable filter ;

• coherent and incoherent integration ;

• automatic false alarm control systems (Constant False Alarm Rate or CFAR systems).

The main principles involved in sizing a maritime surveillance radar system are described using concrete examples. For each of them, we present in particular :

• space scanning modes ;

• the characteristics of the emitted waveform ;

• processing of the receiver's output signal to optimize the probability of detection on the target class in the environment under consideration, while guaranteeing the False...