Design Of Software Module For Demodulation Of Vector Signal In Digital Oscilloscope

With the rapid development of electronic measurement technology,the current measurement instruments are not only limited to the function of a single measurement signal,but also in the time domain,frequency domain,modulation domain and other multi-functional testing.Therefore,the current oscilloscope has become the direction of multi-functional instruments,and the integration of vector signal analysis function into the oscilloscope is the current research hotspot.This paper takes "high definition digital oscilloscope" as the platform,and uses C# language in visual studio in 2017,a vector signal demodulation software module suitable for MPSK,16 QAM,MAPSK and other modulation formats is designed and implemented.In this paper,the demand analysis,basic theory,mathematical model,basic structure of demodulation and the matching filtering,timing synchronization,carrier synchronization,blind equalization and other functional modules involved in the demodulation process are introduced in detail.Matching filter mainly introduces the principle of simple optimal matching and the code realization process of matching filter in software design.Matching filtering mainly introduces the simple best matching principle and the code realization process of matching filtering in software design.In timing synchronization,Gardner algorithm,which is not sensitive to phase error in timing error detection,is selected as the error detection algorithm.In the aspect of timing error correction,interpolation filter based on Farrow structure is selected as the correction structure,and finally the timing error correction loop is simulated and analyzed.In carrier synchronization,the structure of carrier synchronization and the applicability and advantages and disadvantages of phase error detection algorithms such as decision-oriented(DD)algorithm,simplified constellation(RC)algorithm,polarity decision algorithm,frequency discrimination phase(PFD)algorithm are analyzed.Finally,the frequency discrimination phase algorithm is selected as the error detection algorithm in carrier loop,and the implementation structure of carrier loop is designed The carrier synchronization is simulated and analyzed.In blind equalization,the theoretical analysis of blind equalization is mainly introduced,including the least mean square error(LMS)algorithm,constant modulus blind equalization(CMA)algorithm and multi-mode blind equalization(MMA)algorithm.Finally,the paper tests the above function modules and the whole function of the demodulation system,the test results show that the timing synchronization module can accurately capture the symbol points,and the loop convergence performance is good;the carrier synchronization module can quickly capture the phase error and accurately track to the convergence state,and realize the frequency offset acquisition range of-1MHz~1MHz;the blind equalization can make the symbol points between Finally,the results of various demodulation parameters show that the performance of the demodulation system is good and meets all kinds of design indicators,which shows the effectiveness and feasibility of all kinds of algorithms described in the paper.