C/N0 Inversion for soil moisture estimation using land-reflected bi-static radar measurements

Soil moisture can be processed with the difference of power between a direct and a nadir GNSS signal reflected by the soil. The estimate carrier to noise ratio C/N₀ is a classical measure of power for the GNSS signals. We show in this paper that the classical estimate of C/N₀ processed for one satellite depends on the carriers, code and phase delay of the visible satellites. This dependence decreases the reproducibility of the measurements. In this paper we propose a non-linear model that links the power of the satellites with the observations of correlation obtained for the in phase component of the prompt local code. This expression takes into account the parameters of the GNSS signal and allows to improve the reproducibility of measurements. Unfortunately the expression is non linear and a particle filter is used to recover the signals amplitudes from the observations of correlation. In the experimentation the proposed approach is assessed on synthetic signals in the dynamic and static case.