Effects of GNSS Receiver Tuning on the PLL Tracking Jitter Estimation in the Presence of Ionospheric Scintillation

K Guo,S Vadakke Veettil,M Aquino

doi:10.1029/2019sw002362

Abstract

AbstractIonospheric scintillation is an interference characterized by rapid and random fluctuations in radio frequency signals when passing through irregularities in the ionosphere. It can severely degrade the performance of Global Navigation Satellite System (GNSS) receivers, thus increasing positioning errors. Receivers with different tracking loop bandwidths and coherent integration times perform differently under scintillation. This study investigates the effects of GNSS receiver tracking loop tuning on scintillation monitoring and Phase Locked Loop (PLL) tracking jitter estimation using simulated GNSS data. The variation of carrier to noise density ratio (C/N0) under scintillation with different tracking loop settings is also studied. The results show that receiver tuning has a minor effect on scintillation indices calculation. The levels of C/N0 are also similar for different PLL bandwidths and integration times. Additionally, the tracking jitter is estimated by theoretical equations and verified using the relationship with the PLL discriminator output noise, which is calculated using the post‐correlation measurements. Novel approaches are further proposed to calculate 1‐s scintillation index, which enables to compute the tracking jitter at a rate of 1 s. It is found that 1‐s tracking jitter can successfully represent the signal fluctuations levels caused by scintillation. This work is valuable for developing scintillation sensitive tracking error models and is also of great significance for GNSS receiver design to mitigate scintillation effects.

Highlights

Ionospheric scintillation refers to the rapid and random fluctuations in radio frequency signal amplitude and phase
This study investigates the effects of Global Navigation Satellite System (GNSS) receiver tracking loop tuning on scintillation monitoring and Phase Locked Loop (PLL) tracking jitter estimation using simulated GNSS data
The rapid fluctuations caused by scintillation in the incoming carrier phase will increase the Phase Locked Loop (PLL) tracking errors, which lead to a higher probability of cycle slip (Humphreys et al, 2010); when the increased tracking error exceeds the pull‐in range of the discriminator, a loss of phase lock may occur (Kaplan & Hegarty, 2017)

Summary

Introduction

Ionospheric scintillation refers to the rapid and random fluctuations in radio frequency signal amplitude and phase. Knight and Finn (1998) studied scintillation stochastic models and developed an approach to evaluate the scintillation effects on Global Positioning System (GPS) They pointed out that the levels of scintillation required to cause signal loss depends on the receiver tracking loop bandwidth, filter order, and discriminator type. Rougerie et al (2016) studied the effects of GNSS receiver PLL bandwidth tuning on scintillation indices calculation. The cut‐off frequency can affect the shape of the phase spectrum These analyses only focus on scintillation indices estimation with different receivers or receiver tracking loop parameters. This study focuses on (1) understanding the effects of receiver tuning on scintillation monitoring and tracking jitter estimation under scintillation; (2) verifying the relationship between the tracking jitters estimated by theoretical models and calculated by the PLL discriminator output.

Ionospheric Scintillation

PLL Tracking Loop Models and Tracking Jitter Under Scintillation

Experimental Setup and Data Processing Flow

Scintillation Index Calculation With Receiver Tuning

PLL Tracking Jitter Validation Using the Discriminator Output

Conclusions and Remarks