Design and implementation of a high-frequency software-defined radar for coastal ocean applications
In 1955, Crombie [1] identified that when an electromagnetic wave is transmitted from a shore-based high-frequency (HF) radar, operating at 13.56 MHz, the Doppler spectrum of sea echo yielded a resonant backscatter phenomenon known as Bragg scattering, which results from coherent reflection of the transmitted energy by ocean surface waves (SWs) whose wavelength is exactly half as long as the transmitted radar waves. Around 17 y later, Barrick introduced the first- and second-order theory for deriving the HF ocean radar cross section, paving the way for using HF-SW radar (3–30 MHz) in remote sensing of the sea state [2]–[4]. Since then, design and implementation of classical HF radars have proliferated [5], with Coastal Ocean Dynamics Applications Radar and Wellen/Wave Radar (WERA) probably among the most popular [6], [7]. These radars use traditional, fixed, and dedicated hardware implementations. An outcome is that this approach limits the flexibility of these classical systems and potentially increases their cost.