GPS Carrier Phase Spectrum Estimation for Ionosphere Scintillation Studies

GPS signal carrier phase spectrum is an important measure of ionosphere scintillations. The conventional means of obtaining the carrier phase spectrum is performing FFT of detrended carrier phase estimation generated by the carrier phase lock loop (PLL). The PLL is a feedback system whose outputs are influenced by the system parameters and are not the true representation of the input phase. In this paper, we use simulated GPS signals to demonstrate the distortion of the input carrier phase spectrum by the PLL and receiver noise. An inverse filter and high frequency receiver subtraction method are cascaded following the PLL to restore the original input carrier phase spectrum. The carrier phase spectrum restoration method performance is evaluated using both simulated and real scintillation signals.