The Frequency-domain Algorithm Of Pulse Track Circuit Based On FPGA

The track circuit is one of the infrastructures for train running to achieve automatic control and remote control,one of the important facilities to ensure the safety of railway transport,it is also an important interlocking equipment of railway communication signal system,at the same time which can detect whether there is a train stop in the interval or the station and reflect the idle condition or occupancy state of track.Because of the strong anti-interference ability,the stable performance and other advantages of the high-voltage asymmetry pulse track circuit,it is widely used in DC,AC electrified railway stations and sections.The operating environment of track circuit is complex,so the pulse signal will be from external or internal pulse,random and periodic interference resulting in errors and even mistakes.Because of the interference effects,the receiving equipment can not accept the asymmetric pulse signals correctly.Therefore,in order to receive the accurate high-voltage asymmetry pulse signal,how to effectively filter out the interference of track circuit is very important for the analysis of the track state.According to the characteristics of the high-voltage asymmetry pulse track signal,this paper has solved the problem of asymmetric shock pulse signal pulse interference using effective methods of adaptive filtering in order to judge the track status information more correctly.Based on the theory of adaptive filtering,this paper has created a new adaptive filter model,and come up with an Least Mean Square(LMS)algorithm which combines the time-domain with the variable step in the frequency-domain algorithm.By the MATLAB simulation of time-domain LMS,frequency-domain block LMS,VSSNLMS algorithm and the improved LMS algorithm in this paper,the analysis results show that the new algorithm has the fastest convergence rate and the highest signal to noise ratio.Its SNR is higher than the VSSNLMS algorithm about 3dB,than the frequency-domain block LMS algorithm and time-domain LMS high about 10 dB and 3dB respectively,has a good filtering effect;and its convergence rate is faster than the time-domain algorithm about 50%,than the frequency-domain block LMS algorithm and the VSSNLMS algorithm about 25%and 16%respectively.Therefore,the improved algorithm has better effect when it was used in filtering the actual signal of the track.Finally,the FPGA simulation of LMS algorithm is completed on the ISE platform according to the parameters of MATLAB simulation,and by frequency-domain analyzing the worked signal on FPGA,the track circuit running status in the high-voltage asymmetry pulse track circuit system has been assessed correctly,and then the results have been uploaded in first bit machine for analysis,preservation and display.The algorithm proposed in this paper can provide a reference for the effective filtering of high-voltage asymmetric pulse signal.