Measuring the Directional Ocean Spectrum from Simulated Bistatic HF Radar Data

Abstract

HF radars are becoming important components of coastal operational monitoring systems particularly for currents and mostly using monostatic radar systems where the transmit and receive antennas are colocated. A bistatic configuration, where the transmit antenna is separated from the receive antennas, offers some advantages and has been used for current measurement. Currents are measured using the Doppler shift from ocean waves which are Bragg-matched to the radio signal. Obtaining a wave measurement is more complicated. In this paper, the theoretical basis for bistatic wave measurement with a phased-array HF radar is reviewed and clarified. Simulations of monostatic and bistatic radar data have been made using wave models and wave spectral data. The Seaview monostatic inversion method for waves, currents and winds has been modified to allow for a bistatic configuration and has been applied to the simulated data for two receive sites. Comparisons of current and wave parameters and of wave spectra are presented. The results are encouraging, although the monostatic results are more accurate. Large bistatic angles seem to reduce the accuracy of the derived oceanographic measurements, although directional spectra match well over most of the frequency range.

Measurement of Sea Waves

“…HF radars can be roughly divided into two categories: direction-finding and beam-forming (or phased array, for a recent assessment of the performance of both kinds of systems see [65]). In order to exemplify the potential of a coastal HF radar for measuring waves, we will look at results obtained with systems belonging to the first group, and in particular with SeaSonde ones, manufactured by CODAR Ocean Sensors (where CODAR originally stands for Coastal Ocean Dynamics Applications Radar [66]), which are compact radars that compare phases and amplitudes of backtransmitted signals using direction-finding inversion algorithms.…”

Sea Echoes for Airborne HF/VHF Radar: Mathematical Model and Simulation

“…For backscattering, the angle of reflection θ s is identical to the angle of incidence θ i , i.e., θ i = θ s . As mentioned in [14,15], when L is very big, i.e., L → +∞ is assumed, the integration interval of the Stratton-Chu integral can also be set…”

“…For the SPM, Hisaki [14] considered the effect of finite illumination area to derive the NRCS for shore-based monostatic HF radar. More recently, Hardman et al [15] also presented the shore-based bistatic NRCS utilizing the SPM. Besides that, Srivastava and Walsh [16,17] proposed a generalized function method (GFM) to analyze the scattered field from the sea surface and derived the NRCS for the shore-based monostatic HF radar.…”

Vessel Velocity Estimation and Tracking From Doppler Echoes of T/R-R Composite Compact HFSWR

“…However, limited by the coarse bearing resolution due to reduced aperture size, compact HFSWR system operated in monostatic mode is difficult to provide accurate target position information. Plenty of researches have demonstrated the effectiveness of a bistatic HFSWR in both sea state estimation [13][14] and target detection [15], but similar problems exist if a compact system is used.…”