“…However, a drawback of non-coherent MRs is the need for a modulation transfer function (MTF) to calibrate the radar spectrum and get a reliable estimation of the sea state parameters (significant wave height, period, and wavelength) [17], [22], [23]. Differently from non-coherent MRs, coherent systems take into account also the phase of signal or the target radial velocity (Doppler shift), from which it is possible to retrieve the significant wave height and 2D directional spectra, and quantify some physical characteristics of the sea wave [24], [25]. Moreover, coherent MRs do not require the calibration of the radar spectrum needed by non-coherent systems [24].…”