An Inverse Diffraction Technique for Scaling Measurements of Ionospheric Scintillations on the GPS L1, L2, and L5 Carriers to Other Frequencies

To predict the impact of ionospheric scintillations on communications, navigation, and space radar systems it can be useful to simulate the RF conditions under which these systems must operate. GNSS satellites broadcast radio signals that can be monitored by receivers on the ground to specify scintillations at multiple frequencies in the L band range. In this paper, we describe an inverse diffraction technique for mapping the deterministic structure of GPS scintillations measured at the L1, L2, and L5 frequencies to other frequencies. In the case of weak scatter, a statistical theory that describes how the S4 index scales from one frequency to another is well established (Rino, Radio Sci., 14, 1135, 1979). However, this statistical scaling breaks down when the S4 index at either frequency saturates due to multiple scatter effects. The inverse diffraction technique can be used under both weak and strong scatter conditions, and it works as follows. The complex signal fluctuations on the ground are backpropagated up to ionospheric altitudes to infer an equivalent phase screen. Forward-propagation through a wavelength-scaled version of this screen provides a realization of the complex fluctuations at the desired operating frequency. Using 50 Hz