Simulating Ionosphere-Induced Scintillation for Testing GPS Receiver Phase Tracking Loops

A simple model is proposed for simulating equatorial transionospheric radio wave scintillation. The model can be used to test Global Positioning System phase tracking loops for scintillation robustness because it captures the scintillation properties that affect such loops. In the model, scintillation amplitude is assumed to follow a Rice distribution, and the spectrum of the rapidly-varying component of complex scintillation is assumed to follow that of a low-pass second-order Butterworth filter. These assumptions are justified, and the model validated, by comparison with phase-screen-generated and empirical scintillation data in realistic tracking loop tests. The model can be mechanized as a scintillation simulator that expects only two input parameters: the scintillation index S ₄ and the decorrelation time tau₀. Hardware-in-the-loop tests show how the model can be used to test the scintillation robustness of any compatible GPS receiver.