Research And Implementation Of Improved TVM430 Signal Based On TMS320C6722 Platform

TVM430 is a digital coding track circuit signaling system, which imported from France. TVM430 can transfer a maximum of 21 bits train control information with multi-tone FM signal, so it can well meet the requirement of railway development on the amount of control information. But the flaws are equipments expensive and long decode cycle.2.5-3s decode cycle is much longer than ZPW2000. Long system response time limits the application of TVM430 in high-speed railways, so decode cycle reduction is the oriented of our system design in this paper.Two methods can be used to reduce decode time. First, improve the signal design and optimize the decode algorithm, both of them can reduce the computation. Second, improve the hardware performance.Improved TVM430 reduces the unnecessary redundant information while ensuring the information of China's railway required. TMS320C6722 is a new generation of TI's high-performance floating-point DSP chip, which has optimized system architecture, powerful parallel processing capabilities and Rich on-chip peripheral. All of these features make it a perfect solution of improved TVM430.This paper is based on the TMS320C6722 floating-point DSP platform to research and develop the improved TVM430, including two parts:Tx and Rx.DDS solution is used to implement signal transmission. The process of Tx include three steps. First, CRC encode to get code word; second get modulation signal sampling sequence in the method of look-up table; third, calculate the instantaneous frequency of multi-tone FM, then write the frequency control word to frequency registers of DDS. Rx can be divided to three steps to achieve. First, demodulate the FM signal get Modulated signal. We use across-zero detection method in this paper to do FM demodulation, which can effectively avoid the interference caused by the parasitic amplitude modulation. Then, analyze the spectrum of modulated signal. The spectrum of modulated signal by directly FFT cannot meet the frequency resolution of signal analysis. So ZFFT is used to enlarge the frequency resolution. Finally, get code word of Tx by analyze is the peak exist in the low-frequency corresponding the information bit.