The Design Of Constant Envelope Of Navigation Signals And Assessment Of Navigation Signals

With the accelerated upgrade of GPS and GLONASS navigation systems whichhave been built, the navigation signal system has the rapid pace of change. The newnavigation signal has completely different properties with the BPSK signal. With theimplementation of the GPS modernization, the new military M-code is used on L1andL2frequencies. Galileo system uses the MBOC, ALTBOC, BOC and other BOCmodulations. Due to its good spectral isolation and the advantages of the high trackingaccuracy, BOC modulation makes signal design for global satellite navigation systeminto a whole new stage. It proposed new requirements for constant envelope of signalsand quality assessment of navigation signals under the new navigation system. Based onthe new navigation system, the main contents and contributions of this thesis are asfollows:1) With the expanding necessary of global navigation satellite system in civilianas well as military. Building a transition period of a navigation system which cancompatible with the pre and post signals, more of the downlink signals need to beadvertised to the ground in single frequency. But the navigation payload is a powerconstrained system, a plurality of signals should be modulated on the same frequency.Taking into account the nonlinear characteristics of the high power amplifier,multi-channel signals are need to achieve constant envelope modulation in baseband.This can reduce the nonlinear distortion of the signal through the high power amplifier.In this thesis, simulated the current foreign navigation signal constant envelope whichhas proprietary. Compared the pros and cons of different constant envelope. This thesismakes suggestions for constant envelope under different numbers of signals or differentratio of power.2) At the same time, the signal quality assessment under the new navigationsystem has also become an important issue. This paper focuses on the following threeindicators: correlation-loss, IQ imbalance and code phase consistency. Distinguish thedefinition of correlation-loss between single signal and multi-channel signals, andderived the physical significance of correlation-loss from the definition. Due to the high requirement of IQ imbalancement accuracy, this thesis corrects the measurement of IQimbalancement by code cross-correlation.3) Finally, according to a large amount of simulation results can make the followconclusions: the necessity of constant envelope modulation is verified by thecomparison of correlation-loss results which are get from constant envelope signal andnon-constant envelope signal through high power amplifier; according to the result ofthe constant envelope signal through different channels, when the power of constantenvelope signal is set in saturation point of high power amplifier can improve thecorrelation-loss; according to the result of constant envelope signal through differentfilters, the nonlinearity of the group delay characteristic of the IIR filter will result in thedeterioration of code phase consistency and IQ imbalance.