| In order to meet the needs of multi field applications,various satellite navigation systems are committed to upgrading and technological innovation.The new generation of satellite navigation systems mostly use multiplexed signals,which puts forward higher requirements for signal design and signal quality evaluation technology.In modern navigation signal design,transmission channel distortion impact analysis and signal envelope research are one of the key problems to improve navigation performance.Signal quality evaluation technology is an important guarantee for navigation system to provide normal application services.This paper focuses on the influence of transmission channel distortion on the quality of constant envelope and non-constant envelope signals and the analysis method of signal anomaly based on the results of signal quality evaluation.The main results are as follows:(1)The generation mechanism and characteristics of constant envelope and nonconstant envelope signals are deeply studied to realize the simulation generation and analysis of constant envelope and non-constant envelope signals of Beidou B1 signal.It is proposed to take the multiplexed signal as the research object of channel distortion,which improves the deficiency of traditional analysis methods that only analyze the influence of transmission channel distortion on single system signalStarting from the definition and characteristics of constant envelope and nonconstant envelope signals,the specific implementation methods of constant envelope multiplexing based on Phase Optimized Constant Envelope Transmission(POCET),Asymmetric Constant Envelope Binary Offset Carrier(ACE-BOC)and Dual Quadrature Phase Shift Keying(Dual QPSK)technology and non-constant envelope multiplexing based on Tricode Hexaphase Modulation(THM)are studied and given.POCET and THM technologies are used to realize the multiplexing and synthesis of B1 constant envelope and non-constant envelope signals of Beidou navigation satellite system(BDS),which provides an important basis for subsequent research.(2)This paper studies the characteristics of satellite navigation signal transmission channel,establishes linear and nonlinear distortion models based on the whole link transmission channel,and realizes the design and development of simulation model softwareBased on the full link transmission channel,the nonlinear distortion factors are refined,and the combined model of pre power amplifier filter and high power amplifier is established;The linear distortion factors are refined,and the models of band limited distortion,amplitude ripple distortion,amplitude asymmetric distortion,phase ripple distortion,quadratic phase distortion and cubic phase distortion are established.Design and develop the analysis software of the influence of transmission channel distortion on signal quality.The software can realize the simulation analysis of the influence of single distortion and combined distortion on signal quality,and can provide important technical support for the research of transmission channel distortion.(3)The influence of single and combined distortion of non-ideal characteristics of common channels on the quality of constant / non constant envelope signal is studied,and the influence degree and variation law of various distortions on signal quality are clarified.By analyzing the measured data,the L1C/A signal performance comparison between new satellite and old satellite in the global positioning system(GPS)system and the interoperability signal performance comparison between BDS B1 Cd and GPS L1 Cd are realizedThe performances of constant / non constant envelope signals under the influence of nonlinear distortion and linear distortion are compared,and the measured data of GPS and BDS are evaluated and analyzed.Under nonlinear distortion,the research results show that the filtering effect before power amplifier will destroy the constant envelope characteristic of signal;Under the parameter setting in this paper,it is suggested that the optimal bandwidth of the filter before the power amplifier of the constant envelope signal is 50 MHz and the optimal bandwidth of the non-constant envelope signal is 40 MHz.Under linear distortion,the results show that the constant envelope signal has smaller ranging deviation under the influence of amplitude distortion;Under the influence of phase distortion,the non-constant envelope signal has smaller ranging deviation.The analysis results of measured data show that in GPS system,new satellite L1C/A signal can achieve better ranging performance;The ranging performance of GPS L1 Cd and BDS B1 Cd signals is equivalent.(4)The feasibility of combining the distortion model with the measured signal quality is established,and a method of combining the distortion model with the measured signal quality is proposed to verify the effectiveness of the proposed data baseIn view of the problem that the current signal quality evaluation results can only judge the quality of the signal and can not directly reflect the cause of the signal abnormality,this paper proposes an effective signal abnormality cause analysis method,evaluates the quality of the measured data of B1 signal for six months,analyzes the distortion cause of the abnormal signal by using the method proposed in this paper,and preliminarily judges the distortion range.After repeated simulation analysis and demonstration,The effectiveness and feasibility of this method are verified. |
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