Researches On Evaluation Methods Of Correlation Domain Characteristics For Multiplexing MBOC Signal

In recent years,the Global Navigation Satellite System(GNSS)has been developed rapidly.With people's increasing demand for location-based service,the application of diversification and high precision has become a trend.A single BPSK modulation has been unable to fully meet the users' needs,and navigation signals' compatibility and interoperability among systems are becoming increasingly prominent.To design the signal with more excellent performance is the indispensible way to modernize the development of satellite navigation system.The Multiplexed Binary O ffset Carrier(MBOC)modulation meets the demand of the new generation of GNSS with another feature that it uses the constant envelope multiplexed technique.The modern GPS?GALILEO and BDS all adopt the MBOC modulation and multiplexed with other signals in the same carrier,Great changes have taken in the MBOC modulation signal compared with multiplexing before,such as severe bending in the second linear region of the filtered correlation curve,difficultly calculating the correlation loss due to power allocation and S-curve having more than one zerocrossing and so on.To carry out the MBOC signal quality evaluation is conducive to timely reflect the distortion of the navigation signal and monitor the working status of satellite payload.In order to be able to accurately and reliably assess the signal quality,it is particularly important to study the signal evaluation method.The thesis studies the evaluating methods of characteristics of correlation domain about multiplexed MBOC signal,the research achievements are as follows:1? The slope and asymmetry o f correlation curve have been analyzed.Because the limited sampling rate and external interference will lead to code phase deviation of correlation peak,Three-point Reconstruction are proposed to calculate the code phase deviation of correlation peak.Power factor compensation methods are proposed to the correlation loss estimation of multiplexed signal,which is difficult to calculate because of mixed correlation loss between power allocation and code-chips mismatch.The experimental results verify the feasibility of the algorithms.2?In the various DLL discriminator algorithms,the S-curve has more than one zero-crossing,and the linear region at the equilibrium point has the very narrow and small slope value,which leads to inaccurate problems for S-curve bias and S-curve slope.The thesis comes up with two detection line methods of Equal-weight Estimation and Randomized Hough Transformation(RHT).The former,including two-point connection and interpolation fitting algorithms,are using two or more points to fit straight line;the latter is to map multiple lines extracted by S-curve to multiple points in the parameterspace,then use K-means and Threshold method s to calculate center-point so as to reckon the S-curve bias and slope.The experimental results verify the feasibility of the algorithms.The RHT has more robust than Equal-weight Estimation.3?Some facts such as coherency,carrier phase bias,baseband signal waveforms are used to evaluate the multiplexed signal quality.O n the basis of the stochastic characteristics that the long time average value of navigation message symbols is zero,The method called Multi-periods C umulative Average is adopted to solve the twine problem that baseband code-chips are difficultly obtained by demodulation due to the same frequency and phase.The thesis aims to carry out the research on the key methods of characteristics evaluation of correlation domain about multiplexed MBOC modulation signal,simulation and actual results verify the correctness and feasibility of the algorithms.Research results and application software from this thesis have performed some services for space signal quality evaluation and provided the support for downlink signal quality evaluation of GNSS.