Embedded Software Design Of Extraction Form The Signals Of Track Frequency Shift Feature

With the development of economy in our country, the railway has been thefast development in our country. The railway has speeded for several times, andhigh-speed rails are put into use. Now railway has become the main transport toolfor people. But with the development of railway, making sure the safety ofrailway has become an important issue. Railway signal equipment is the basicequipment of railage, and is the guarantee of safe operation of train on railway.With the development of railway and the growth of train speed, the requirementof the efficient transportation and the accurate signal analysis turns to be moreand more important. So how to detect the railway running signal in real time andaccurately has become an important topic.In this paper, based on the characteristic of the railway frequency shift, wepropose a detecting system, which can detect the characteristic frequency of therailway frequency shift-carrier frequency and low frequency. This system usesOMAPL137which is made by TI company as the hardware platform. The chiphas double chip which are ARM and DSP, it is a fast-running and low power-costchip.It can not only use the digital signal processing ability of DSP to realize thesignal detecting,but also can use ARM to realize the embedded of Linux anddesign of all kinds of drivers.The characteristic of OMAPL137chip satisfies theneed of this design.Linux is a CPU operating system which has been widely usedrecently. The source code of this system is open, which can be used on manyprocessors as long as do cuts and remove to the core according to the need. Thispaper mainly studies the detecting method of the modulated signal frequency ofUM71jointless track signal and transmitting frequency. When the UM71tracksignal is being detected, a big problem is how to reduce the sample frequency.Since the track signal belongs to the characteristic of narrowband signal, weadopt undersampling method to achieve the reduction of sampling frequency instead of the Nyquist sampling method. Meantime we adopt ZFFT to furtherimprove the resolution ratio of the frequency of the low-frequency signal toachieve the detecting of the characteristic frequency of the frequency shift signal.On the other hand, based on Linux operating system,we design the USB drive,LCD drive, GPIB interface drive, as well as the A/D sampling chip ADS1178drive.Through this design, we basically realize the main function of the detectingsystem, which is the detecting of characteristic frequency of the signals and theset up of the software platform of this system.