Abstract
Currently, shore-based HF radars are widely used for coastal observations, and airborne radars are utilized for monitoring the ocean with a relatively large coverage offshore. In order to take the advantage of airborne radars, the theoretical mechanism of airborne HF/VHF radar for ocean surface observation has been studied in this paper. First, we describe the ocean surface wave height with the linear and nonlinear parts in a reasonable mathematical form and adopt the small perturbation method (SPM) to compute the HF/VHF radio scattered field induced by the sea surface. Second, the normalized radar cross section (NRCS) of the ocean surface is derived by tackling the field scattered from the random sea as a stochastic process. Third, the NRCS is simulated using the SPM under different sea states, at various radar operating frequencies and incident angles, and then the influences of these factors on radar sea echoes are investigated. At last, a comparison of NRCS using the SPM and the generalized function method (GFM) is done and analyzed. The mathematical model links the sea echoes and the ocean wave height spectrum, and it also offers a theoretical basis for designing a potential airborne HF/VHF radar for ocean surface remote sensing.
Highlights
The sea echoes of HF or VHF ocean radars contain rich information about the sea surface since the length of the HF/VHF radio wave is very close to the wave length of gravity wave at the ocean surface [1]
The objective of this paper is to investigate the interaction mechanism of HF/VHF electromagnetic waves scattering from the ocean’s surface, and this should provide a theoretical basis for designing novel airborne HF/VHF radars for ocean remote sensing
The sea surface wave height has been expressed as the superposition of two Fourier series which represent linear and nonlinear wave heights
Summary
The sea echoes of HF or VHF ocean radars contain rich information about the sea surface since the length of the HF/VHF radio wave is very close to the wave length of gravity wave at the ocean surface [1]. Along with the development of electronic technology, airborne radars have been widely used for ocean remote sensing [7,8,9]. An airborne VHF radar has been developed for forest remote sensing [10]. All these developments make it possible to design and develop an airborne HF/VHF radar to monitor the sea surface. The objective of this paper is to investigate the interaction mechanism of HF/VHF electromagnetic waves scattering from the ocean’s surface, and this should provide a theoretical basis for designing novel airborne HF/VHF radars for ocean remote sensing
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