Jitter Analysis of QPSK and BOC(n,n)GNSS Signals

摘要

This paper analyzes the effects of jitter on thernGPS and Galileo navigation signals. Jitter effectsrnhave usually been modelled as additive noise,rnbased on a sinusoidal input signal, and limits thernachievable Signal-to-Noise Ratio (SNR). Analysisrnshows that psec-level jitter specifications arernrequired in order to keep jitter noise well belowrnthe thermal noise for software radio satelliternnavigation receivers. However, analysis ofrna BPSK system shows that large errors occur ifrnthe jittered sample crosses a data bit boundary.rnQuadrature Phase Shift Keying (QPSK) modulationrnachieves greater bandwidth efficiency thanrnBPSK. The new GPS L5 signal is QPSK modulated.rnThe Binary Offset Carrier (BOC) spreadingrnmodulation has recently been recommendedrnby GPS-GalileoWorking group on Interoperabilityrnand Compatibility for adoption by Europe’srnGalileo program for its Open Service (OS) signalrnat the L1 frequency and by the United Sates for its modernized GPS L1 Civil (L1C) signal.rnBOC signals have more transitions and hence jitterrncreates more woes. The aim of this paper isrnto derive expressions for noise due to jitter takingrninto account the transitions probability in QPSKrnand BOC systems. Both simulations and analysisrnare used to give a better understanding of jitterrneffects on Software Radio GNSS receivers.