HF Bistatic Ocean Doppler Spectra: Simulation Versus Experimentation

We simulate the Doppler spectra that can be obtained under experimental conditions from bistatic high-frequency oceanic radar. For this, we combine the bistatic second-order theory with the characteristics of the full radar system, such as antenna patterns, range attenuation, and postprocessing of the received signal. Because of the sharp variation of the bistatic geometry at short range, we show that it is crucial to take these effects into account for the correct interpretation of the first-order Bragg peaks. The second-order spectrum is more robust to the system characteristics but can under some conditions also suffer from its artifacts, especially in the vicinity of the secondary peaks. A comparison is made with experimental spectra acquired recently with a Wellen radar system on the Mediterranean coast. The Wave Watch III model is used to simulate directional wave height spectra after a preliminary validation with in situ buoy measurements. Experimental and simulated Doppler spectra agree generally well, except in the case where the directional wave spectrum has little energy in the line of sight of the radar.