摘要
随着铁路技术的高速发展,ZPW-2000无绝缘轨道电路成为了我国轨道交通电路中的主流制式,ZPW-2000轨道移频信号的正确译码是铁路上行车安全的重要保证。目前的译码检测算法主要是基于频谱细化的频谱搜索法(ZFFT、CZT),这些算法都是讨论纯净或高信噪比下的移频信号,随着信噪比的降低,移频信号的谱峰就很容易受到噪声的干扰而出现错误的译码,从而导致频谱搜索法检测失效。对此,本文根据Duffing振子对噪声免疫而对周期微弱信号敏感的特点,给出了基于Duffing振子的低信噪比下移频信号译码及频偏检测新方法,并通过对频偏的检测判定ZPW-2000轨道电路发送及接收设备是否合格。主要研究工作如下：
首先,对Duffing振子进行了分析,了解Duffing振子微弱信号检测原理。总结了混沌判据的常用方法：Lyapunov指数法、Melnikov法、相轨迹法以及阵发性混沌法,并介绍了正弦信号的幅值及频率检测原理。
其次,结合Duffing振子对周期信号敏感的特点,给出了将Duffing振子用于ZPW-2000轨道移频信号译码的新方法。轨道移频信号译码是为了提取移频信号中载频fc和低频fd参数,以获得闭塞分区状态和列控信息。Duffing振子译码移频信号的目的是解决低信噪比环境下移频信号译码能力弱的问题。通过仿真实验验证：该方法可靠性强,能译码出强噪声背景下的移频信号,且具有较低的译码误码率。
然后,将Duffing振子译码移频信号的方法进行改进,实现对ZPW-2000轨道移频信号的频偏检测,以此判定移频电路发送、接收设备是否合格。该方法能实现白噪声及有色噪声背景下的移频信号频偏检测,且40个Duffing振子并行排布,易于硬件实现。
最后,对本论文的研究内容进行总结,找出存在的一些问题和需要进一步研究的内容。
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.
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