Research And Implementation Of Baseband Signal Processing Technologies In PCM/FM Telemetry Communcation Systems

Aircraft telemetry is a measurement technology for object parameters of high-speed aircraft,missiles,spacecraft and other objects.Data transmission is the core of telemetry.The pulse code modulation / FM(PCM / FM)has a strong anti-noise performance,high emission efficiency and strong anti-tail effect.It have a wide range of applications in aerospace.The paper combines the practical application requirements of PCM / FM telemetry receiver,study the baseband signal processing technology.The focuses is on the analysis,design and implementation for the key technologies such as multi-symbol detection(MSD),Turbo product code(TPC)and time-frequency synchronization of telemetry receivers etc.The main contents include the following aspects:(1)Analysis of Index and Design Requirements for Baseband Signal Processing Technology of Telemetry Receiver Based on Engineering Requirement,Design of PCM / FM telemetry receiver baseband signal processing scheme.According to the general scheme proposed in this paper,study the influence of time-frequency synchronization on system bit error rate.The realization parameters of TPC decoding and MSD demodulation algorithm are analyzed and determined by simulation.(2)For the existing MSD technology on the system symbol synchronization requirements are too high which lead to complex control problems.Propose a simplified method of MSD based on sample sliding.On the one hand,simplifies the MSD implementation structure,while reducing the MSD algorithm for symbol synchronization requirements.On the other hand,provide the necessary conditions for the subsequent study of the timing synchronization algorithm.For the MSD technology to achieve the problem of excessive consumption of hardware resources,According to the characteristics of MSD local waveform,optimized for local waveforms,thus reducing the implementation complexity without compromising performance at all.(3)In order to improve the performance of timing synchronization algorithm in PCM / FM telemetry system,taking into account,popose a timing error detection scheme based on MSD soft information,the scheme utilizes the demodulation gain of the MSD soft information itself.Improve the performance of traditional timing error detection scheme.Aiming at the problem of poor ability of carrier synchronization in PCM / FM system,propose a carrier synchronization scheme based on delay-multiplication frequency offset estimation,to solve the low bit rate when the big frequency is difficult to synchronize the problem.The paper also designs and analyzes the system frame synchronization scheme.(4)Research on key technologies combined with MSD,TPC decode,time and frequency synchronization,completed the PCM / FM receiver system in the baseband signal processing technology design and implementation,and test and verify the baseband signal processing in the system of the indicators.The test results show that the gain of 6.5 d B is obtained in the Gaussian channel compared to the traditional demodulation method to meet the design requirements.It is verified that the baseband signal processing scheme is functional in the whole system and can be stable and reliable.