First-order Radar Cross Section Research Articles

Using a second-order bistatic cross-section of the ocean surface for bistatic shipborne HFSWR

ABSTRACTThe second-order radar cross section (RCS) of ocean surface is analytically derived for the case in which the radar transmitter is located inland and the receiving antenna is mounted on a shipborne platform. With our previously derived first-order RCS result, the total RCS of ocean surface is simulated for a variety of radar operating parameters and sea states. According to simulation results, it is seen that the relative effect on the second-order spectra due to the platform motion is much smaller than that on the first-order. For the conditions of the radar working with a high operating frequency or a high sea state, the increase of the second-order spectral energy may contaminate the first-order component severely. The obtained results may be useful for setting appropriate limits on the use of radar operating parameters or the bistatic site geometries, from which condition the ocean surface parameters can be effectively extracted from the radar data.

A First-Order HF Radar Cross-Section Model for Mixed-Path Ionosphere–Ocean Propagation With an FMCW Source

A theoretical model of the first-order high-frequency (HF) radar cross section (RCS) for the ionosphere–ocean propagation involving a frequency-modulated continuous wave (FMCW) source is presented in this paper. Based on previous modeling involving the scattering of HF electromagnetic radiation from the ocean surface, an expression for the first-order electric field with an FMCW source is derived for the mixed-path case in which scattering occurs from both the ionosphere and the ocean surface. Then, this field is Fourier transformed and the frequency distribution of the demodulated electric field indicates range information of the ionosphere–ocean propagation. Subsequently, the first-order RCS is developed by assuming the ocean surface and the ionosphere are stochastic processes. To investigate the power spectrum of this ionospheric-clutter mode and its relative intensity to that of the ocean clutter, a normalized ionospheric-clutter power is simulated. Numerical simulation results are first compared with that of a pulsed radar for the same ocean scattering patch. Subsequently, it is shown how the ionosphere velocities and wavelengths, and wind directions affect the power spectrum for this ionosphere–ocean propagation.

Bistatic High Frequency Radar Ocean Surface Cross Section for an FMCW Source with an Antenna on a Floating Platform

The first- and second-order bistatic high frequency radar cross sections of the ocean surface with an antenna on a floating platform are derived for a frequency-modulated continuous wave (FMCW) source. Based on previous work, the derivation begins with the general bistatic electric field in the frequency domain for the case of a floating antenna. Demodulation and range transformation are used to obtain the range information, distinguishing the process from that used for a pulsed radar. After Fourier-transforming the autocorrelation and comparing the result with the radar range equation, the radar cross sections are derived. The new first- and second-order antenna-motion-incorporated bistatic radar cross section models for an FMCW source are simulated and compared with those for a pulsed source. Results show that, for the same radar operating parameters, the first-order radar cross section for the FMCW waveform is a little lower than that for a pulsed source. The second-order radar cross section for the FMCW waveform reduces to that for the pulsed waveform when the scattering patch limit approaches infinity. The effect of platform motion on the radar cross sections for an FMCW waveform is investigated for a variety of sea states and operating frequencies and, in general, is found to be similar to that for a pulsed waveform.