ZPW-2000 Frequency-Shift Signal Decoding And Frequency Offset Detection Based On Duffing Oscillators

With the rapid development of the railway, ZPW-2000 track circuit has become the mainstream of rail circuits; ZPW-2000 frequency shift signal decoding FSK signals is an important guarantee on the railway traffic safety. Currently, decoding detection algorithm is mainly based on the spectrum of refined search method (ZFFT, CZT), almost all discussion of pure or high signal to nosie rate(SNR) frequency shift signal, with the lower SNR, spectral peak frequency shift is very susceptible to interference noise decoding error. Spectrum detected by the search will fail. Therefore, based on the characteristics of Duffing oscillator noise immunity and sensitivity to cycle weak signal, the thesis was given ZPW-2000 frequency shift signal decoding and frequency offset detection based on Duffing oscillator to judge the qualification of devices to send and receive. Key tasks:First, the Duffing oscillator is analyzed to understand the Duffing oscillator weak signal detection theory. Summarizes the criteria for chaos common methods:Lyapunov exponent method, Melnikov, the phase locus method, the intermittent chaos method, and introduced the sine signal amplitude and frequency detection principle.Second, The Duffing oscillator with a strong sensitivity to the periodic signal is presented for the frequency shift signal decoding based on Duffing. Orbital frequency shift signal decoding is to extract frequency-shift signal carrier frequency fc, and low frequency fd to get the block section status and Train Control information. Duffing oscillator signal decoding purpose is to solve the problem what frequency shift signal is weak decoding in the low SNR environment. The method is reliable, able to decode orbit frequency shift signal in a strong background noise, and have lower decoding error rate.Then, the Duffing oscillator frequency shift signal decoding method to improve, achieve ZPW-2000 frequency shift signal offset detection to judge qualification of frequency shift circuit sending and receiving device. This method can realize low SNR frequency shift signal detection in white noise and colored noise, the 40 Duffing oscillators arranged in parallel, easily implemented in hardware.Finally, content of the thesis is summarized, research the existing problems and need to study content further.