Abstract
UM2000 signal is a type of multi-audio frequency-modulated signal which is widely used for railway blocking. Principles of three typical demodulating algorithms are presented in details in this paper. Bit error rates of the three methods at different SNRs are achieved by Monte Carlo simulation experiments. Among the three algorithms, the quadrature demodulation has the best performance at the real working environment. However, the three methods have the same problem of phase hopping when noise is too strong.
Highlights
With the rapid development of high-speed railway in the world, some of the old track circuits have been unable to meet the requirements in terms of speed and safety
UM2000 signal is a type of multi-audio frequency-modulated signal which is widely used for railway blocking
Bit error rates of the three methods at different SNRs are achieved by Monte Carlo simulation experiments
Summary
With the rapid development of high-speed railway in the world, some of the old track circuits have been unable to meet the requirements in terms of speed and safety. UM2000 joint-less track circuit is a new type of digital coding track circuit applying in high-speed railways. The research of demodulating methods plays a vital role in the railway system. Coherent demodulation and non-coherent demodulation are the two traditional demodulating approaches of frequencymodulated signals. We can get the instantaneous phase of the FM signal by coherent demodulation, and directly obtain the instantaneous frequency by the non-coherent demodulation. That is the difference of the two approaches. From this point, the performances of the following three methods are compared. The three algorithms are differential frequency detection, zero-crossing detection and the quadrature demodulation
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