在不增加设备体积重量以及提高发射功率的前提下,为满足高码率遥测数据传输的需求,现有的脉冲编码调制-频调(Pulse Code Modulation Frequency Modulation,PCM-FM)遥测系统广泛使用多符号检测(Multiple Symbol Detection,MSD)算法和Turbo乘积码(TPC)技术.调制指数是PCM-FM遥测系统中的重要参数之一,对系统带宽和误码率有重要影响.本文分析了MSD多符号检测算法原理,通过计算互相关系数及Matlab仿真,分析了调制指数大小对带宽和误码率的影响,指出将调制指数设置为0.715较为合适;分析了调制指数偏差对信噪比损耗的影响,利用MSD算法的相位网格图分析了调制指数偏差对误码和码同步的影响,指出随机数据比连"0"或连"1"数据具有更好的容忍能力.
Effect Analysis of Modulation Index on the Performance of PCM-FM Telemetry System
To meet the needs of high bit rate telemetry data transmission,existing PCM-FM telemetry systems widely use MSD multi-symbol detection algorithm and TPC encoding and decoding technology,without increasing the volume and weight of the equipment and improving the transmission power.The modulation index is one of the important parameters in PCM-FM telemetry systems,which has a signifi-cant impact on system bandwidth and bit error rate.This article analyzes the principle of MSD multi-symbol detection algorithm.By calculating the cross-correlation coefficient and Matlab simulation,thein-fluence of modulation index size on bandwidth and bit error rate is analyzed.It is pointed out that setting the modulation index to 0.715 is more appropriate.The impact of modulation index deviation on signal-to-noise ratio loss was analyzed,and the phase grid diagram of multi symbol detection algorithm was used to analyze the impact of modulation index deviation on error and code synchronization.The fault-tolerant ability of different types of data on modulation index deviation was pointed out.
pluse code modulation frequency modulation(PCM-FM)multiple symbol detection(MSD)modulation indexdeviationrandom datacontinuous"0"data
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