| ABSTRACT:Currently, railway signal processing equipment of the vehicle uses the TI company’s floating point DSP TMS320VC33as the main processor, but the60MIPS processing capacity is more and more not adapted to the current railway requirement of high speed, reliability and steady, and TI company no longer recommends using this chip so it faces the elimination of VC33. As the constant speed of the train, the demand of vehicle equipment is higher and higher, at the same time requirements of railway signal demodulation is more and more reliable, real-time and accurate. With the development of digital signal processing technology and the increasing maturity of high-performance processor, the study of railway signal detection have abandoned the traditional time domain analysis, generating a lot different kinds of algorithms, such as spectrum analysis method, short time Fourier transform, wavelet analysis, Hilbert huang transform and so on, but because of the limitation of VC33internal resources and operation speed, some algorithm is not widely used, and the traditional DSP application software development is completely controlled by the user’s DSP program, facing high threshold for developers, long software development cycle and poor system reliability. Based on real-time multitasking operating system (RTOS), the design of software can greatly reduce the workload of programming and the possibility of error and it is a tendency in the field of embedded application. Therefore choosing new floating-point DSP, using a real-time operating system and based on this system of railway signal development platform has great practical significance.To solve the above problems and combine previous research results, this paper studies the problem from three aspects.(1) in the aspect of hardware system:comparing several widely used and industrial-grade floating-point DSP processor on the market, this paper selects a new type of floating point digital signal processor OMAPL138,which supports the real-time operating system. The dual-core chip, built-in DSP and ARM, just can replace the current vehicle separation system of DSP and ARM system, which can greatly improve the reliability of the system;(2) in terms of demodulation algorithm:because OMAPL138have practical application in railway signal processing, as the generation CPU chip, it should ensure its reliability and stability. Therefore the paper adopts spectrum identification method widely used in the railway to demodulate shift-frequency railway signal on the system of L138.(3) in the aspect of software design:based on embedded real-time operating system DSP/BIOS, visual configuration tools and a variety of API functions and C language and assembly language, the design makes the signal acquisition, processing and display in the hardware and software interrupts, using task thread pattern of the DSP/BIOS to manage and schedule the program, on OMAPL138hardware platform of railway signal demodulation.Under the condition of no noise, the paper makes two kinds of railway signal analysis. Through the data from the OMAPL138experiment system shows, under ideal condition, the lower-up frequency and carrier frequency’s demodulation error within0.3Hz, modulation frequency demodulation error within the0.02Hz and the improving demodulation speed.Therefore the experiment proves the method is feasible. |
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