Comparisons of a fully coherent and coherent-on-receive marine radar for measurements of wave spectra and surface currents

A new coherent solid state marine radar has been developed for short range coastal ocean remote sensing applications. It has been applied to the measurement of coastal ocean currents and ocean wave spectra, examples of which are reported here. The radar is based on a standard marine radar package, but using a solid state power amplifier incorporated as part of the transceiver subassembly. The solid state transceiver subassembly was developed based on a SMA-connector component prototype that was reported on at the Oceans 2019 Biloxi meeting. A series of parallel tests were run with a prototype coherent-on-receive radar, which is based on modifications to a standard Koden marine radar. For the latter, the leakage signal of the transmitted pulse is used as the reference for realigning the phase of the received echo. Due to the non-coherent nature of magnetron sources used for marine radars, the pulse-topulse stability of the transmitted frequency of such a system creates problems with pulse-pair phase-differencing estimates of Doppler shifts. This effect creates a rather noisy Doppler image, and mean Doppler estimates over many rotations can be in error. Data were collected with the pair of radars during the passage of 2-m waves up to 13-s period at the FRF pier in Duck NC. We report on differences in Doppler estimates for the fully coherent and coherent-on-receive marine radars for data collected during this storm, comparing with FRF measurements of wave spectra and surface currents.