Abstract
A new method for the characterization of the sea clutter in high-frequency surface wave radars is presented. The method is applied for the bistatic and the monostatic case. This method is based on the discretization of the sea surface in multiple patches. The fields diffracted by each patch are determined. Subsequently, the voltage that the diffracted fields induce on the receiving antenna is calculated. The sum of the voltages induced by all the patches is the sea clutter to be characterized. The fields diffracted by the sea patches are characterized in the form of field charts on a Huygens surface surrounding each patch. Field charts are modeled by analytical expressions. The current induced on the receiving antenna by the diffracted fields is calculated by means of the Lorentz reciprocity theorem. The feasibility of the method of characterization of the sea clutter is verified by means of the characterization of the fields diffracted by a single patch. The calculation of the induced current is done using the diffracted fields that are reconstructed from the analytical expressions that model them. It is also verified that the transmitting and receiving antenna can be replaced by plane wave sources, in order to simplify the calculations of the radiated fields that take part in the Lorentz reciprocity theorem. As a validation of the proposed method, the Doppler spectrum of a moving sea surface is calculated for the monostatic case.
Highlights
F OR the maritime surveillance of the Exclusive Economic Zone (EEZ) of France, up to distances of 370 km from the coasts, high-frequency surface wave radars (HFSWR) are used [1]
We find the Kirchhoff approximation, the small perturbation method (SPM), the two scale method (TSM), and the small slope approximation (SSA)
The objective is to demonstrate the feasibility of using analytical expressions to approximate the field charts on each of the faces of the Huygens surface and to calculate the voltage induced on the receiving antenna from the reconstructed charts, by means of the Lorentz reciprocity theorem. With this objective in mind, the field charts for the four lateral faces and the top face were interpolated as described in the previous section, for 20 frequencies spaced between 9 and 20 MHz
Summary
F OR the maritime surveillance of the Exclusive Economic Zone (EEZ) of France, up to distances of 370 km from the coasts, high-frequency surface wave radars (HFSWR) are used [1]. The high-frequency (HF) band is chosen for these radars because at this frequency band, the radio range is greater. In HF, the interference due to the sea clutter is greater as well. It is important to appropriately characterize the magnitude of the sea clutter. The characterization of the sea clutter has been done through the calculation of the radar cross section (RCS) of the sea surface. Statistical and analytical methods have been employed
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