基于VMD-希尔伯特变换的机车信号解调方法  

Cab signal demodulation method based on VMD and Hilbert transform

作　　者：杨城 刁艳美 刘颂 YANG Cheng;DIAO Yanmei;LIU Song(Nanjing Tech University Pujiang Institute,Nanjing 211200,China)

机构地区：[1]南京工业大学浦江学院,南京211200

出　　处：《铁路计算机应用》2025年第2期76-82,共7页Railway Computer Application

基　　金：南京工业大学浦江学院校级课题专项资金资助(njpj2022-1-19)。

摘　　要：为了提高机车信号的解调精度,提出一种基于参数优化变分模态分解(VMD,Variational Mode Decomposition)和希尔伯特变换的机车信号解调方法。通过最小均方(LMS,Least Mean Square)自适应滤波器对机车天线采集的信号进行滤波;以Pearson相关系数为评价指标优化VMD参数,利用VMD对滤波后的信号作模态分解;将每个固有模态(IMF,Intrinsic Mode Function)作希尔伯特变换,构建复数解析式,计算得出机车信号的载频和低频调制信号频率;通过计算机仿真验证该方法在谐波环境下的可行性及解调精度;最后,基于Cortex-M4内核单片机搭建程序运行硬件平台,基于直接数字合成(DDS,Direct Digital Synthesis)器AD9854搭建机车信号发生电路,在渐变频移键控(Ramped FSK,Ramped Frequency-Shift Keying)模式下,产生正交FSK信号,模拟现场机车信号测试环境。通过硬件测试,在低信噪比条件下,载频和调制低频解调的最大误差分别不超过0.1 Hz和0.05 Hz。试验结果表明,该方法具有较强的抗谐波干扰的能力,能够准确解调机车信号。In order to improve the demodulation accuracy of cab signals,this paper proposed a cab signal demodulation method based on parameter optimized Variational Mode Decomposition(VMD)and Hilbert transform.The paper used the Least Mean Square(LMS)adaptive filter to filter the signals collected by the locomotive antenna,used correlation coefficient as the evaluation index,optimized VMD parameters,and used VMD to perform modal decomposition on the filtered signal,applied Hilbert transform to each Intrinsic Mode Function(IMF),constructed complex analytical expressions,and calculated the carrier frequency and low-frequency modulation signal frequency of cab signals,verified the feasibility and demodulation accuracy of this method in harmonic environments through computer simulation.Finally,the paper built a hardware platform for program execution based on the Cortex-M4 core microcontroller,build a cab signal generation circuit based on the Direct Digital Synthesis(DDS)device AD9854.This circuit generated orthogonal FSK signals in Ramped Frequency Shift Keying(FSK)mode to simulate the on-site cab signal testing environment.Through hardware testing,under low signal-to-noise ratio conditions,the maximum error of carrier frequency does not exceed 0.1 Hz,and the maximum error of modulation low-frequency demodulation does not exceed 0.05 Hz.The experimental results show that this method has strong resistance to harmonic interference and can accurately demodulate cab signals.

关 键 词：机车信号 变分模态分解 希尔伯特变换 直接数字合成技术 渐变频移键控 正交频移键控 

分 类 号：U284.46[交通运输工程—交通信息工程及控制]