Link Budget Analysis for GNSS-R Sea Surface Return in Arbitrary Acquisition Geometries Using BA-PTSM

Abstract

In this article, we present a link budget analysis for Global Navigation Satellite System (GNSS) signals scattered off the sea surface in arbitrary acquisition geometries. The aim of our study is to investigate the reliability of the Geometrical Optics (GO) scattering model, which accurately describes sea surface scattering at and near the specular reflection direction, in properly modeling the sea surface return in far-from-specular acquisition geometries, which are of interest for maritime surveillance purposes and where GO is expected to fail. To this end, we adopted the recent Bistatic Anisotropic Polarimetric Two-Scale Model (BA-PTSM), which revealed good agreement with advanced scattering models, such as the second-order Small Slope Approximation (SSA2), regardless of the acquisition geometry, with the advantage of a reduced computational complexity. Numerical results have been derived for both circular polarization channels and for both spaceborne and airborne GNSS-Reflectometry (GNSS-R). It has been shown that, as long as conventional GNSS-R processing is assumed, GO can be safely adopted for simulation and analysis of spaceborne GNSS-R data regardless of the acquisition geometry and sea state, whereas more accurate scattering models, e.g., BA-PTSM, should be used for airborne receivers in far-from-specular configurations.

Dual-Frequency Signal Enhancement Method of Moving Target Echoes for GNSS-S Radar

“…Since the signals of the two frequencies f c1 and f c2 are transmitted by the same satellite, the bistatic angle α is same, and the phase difference in the echoes of the two frequency signals is mainly caused by the difference in wavelength. The phase scaling factor k is defined as shown in Equation (12).…”

“…In order to realize the phase difference correction of the dual-frequency signal, it is very necessary to correct the slope and initial phase of the two frequency echo signals to be consistent. For the correction of the signal phase slope, the correction coefficient k is calculated according to Equation (12). Then, the phase of the B3 signal is multiplied by the correction coefficient k for correction.…”

“…A maritime target detection test was carried out in references [10,11], which verified the feasibility of using GNSS signals for target detection. In reference [12], the system link budget using GNSS signals for detection was analyzed, and it was pointed out that when limited by the signal power of GNSS, the realization of target detection requires longterm integration. In reference [13], a signal processing architecture for GNSS-based radar was proposed that utilizes correlation operations between direct signals and reflected signals to improve the processing gain of reflected signals.…”