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ZPW-2000 signal demodulation method based on nonlinear least square method

A technology of ZPW-2000 and least square method, which is applied in the direction of carrier adjustment, modulated carrier system, frequency modulation carrier system, etc., can solve problems such as offset, difficult to guarantee demodulation accuracy, and shortened effective signal sampling duration

Inactive Publication Date: 2019-04-16
LANZHOU JIAOTONG UNIV
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AI Technical Summary

Problems solved by technology

Since the distribution of the frequency components of the ZPW-2000 signal is relatively concentrated, and the periodogram method has a spectrum leakage phenomenon, the leakage value of the carrier frequency component with greater energy tends to shift the peak position of the nearby side frequency component with less energy. When the duration is small, this offset phenomenon will be more serious. At this time, the demodulation accuracy of the periodogram method will be greatly reduced, and it is difficult to guarantee the demodulation accuracy.
When the train passes through a short turnout section at high speed and the signal is affected by transient impact interference, the sampling duration of the effective signal is shortened, and the demodulation accuracy of the periodogram method will be challenged

Method used

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  • ZPW-2000 signal demodulation method based on nonlinear least square method
  • ZPW-2000 signal demodulation method based on nonlinear least square method
  • ZPW-2000 signal demodulation method based on nonlinear least square method

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Embodiment 1

[0132] Embodiment 1, in order to test the demodulation accuracy of the present invention, in the present embodiment, simulation generates different sampling durations, under 144 kinds of carrier frequency, low frequency configuration scheme, Gaussian white noise signal-to-noise ratio, sampling frequency are respectively 30dB, 8000Hz ZPW-2000 simulation signal. Among them, Gaussian white noise signal-to-noise ratio is defined as σ 2 is the variance of Gaussian white noise. Using the method of the present invention, under-sampling zero-filling method and Zoom-FFT interpolation method to demodulate the simulated signal, the average absolute error of the carrier frequency and the low frequency are obtained as follows: figure 2 , as shown in Figure 3. It should be pointed out that in embodiment 1 and the following embodiments, ω of the present invention rp =2π·(0.0005 / 8000)(rad / sample), meanwhile, through zero padding, the frequency domain sampling interval of FFT in the unde...

Embodiment 2

[0134] Embodiment 2, in order to test the real-time performance of the present invention, in this embodiment, the simulation generates ZPW-2000 frequency shift signals with carrier frequency, low frequency and sampling frequency of 2001.4Hz, 29Hz and 8000Hz respectively under different sampling durations. By adopting the method of the present invention, the undersampling zero padding method and the Zoom-FFT interpolation method demodulate each kind of simulation signal 1000 times respectively, and the average running time is obtained as Figure 5 shown. It should be pointed out that the running time recorded in the simulation does not include the time spent on step A since step A can be completed before the signal is received. It can be seen that although the average running time of the present invention is higher than that of the undersampling zero padding method and the Zoom-FFT interpolation method, it does not exceed 0.32s. Therefore, the present invention can make the re...

Embodiment 3

[0135] Embodiment 3, in order to test the anti-white noise ability of the present invention, in this embodiment, different Gaussian white noise signal-to-noise ratios are generated by simulation, and under 144 kinds of carrier frequency and low frequency configuration schemes, the sampling duration and sampling frequency are respectively 0.3s , 8000Hz ZPW-2000 frequency shift signal. By adopting the present invention, under-sampling zero-filling method and Zoom-FFT interpolation method are used to demodulate the simulated signal, and the average absolute error of carrier frequency and low frequency is obtained as follows: Image 6 , Figure 7 shown. It can be seen that, compared with the Zoom-FFT interpolation method, the present invention requires that the average absolute error of carrier frequency and low frequency estimation tends to be stable after the signal-to-noise ratio is greater than or equal to -2dB. This is because in the present invention, the judgment conditio...

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Abstract

The invention discloses a ZPW-2000 signal demodulation method based on a nonlinear least square method. The method is based on a nonlinear least square rule, and includes the five steps of data preprocessing, coarse estimation, grid searching and exact searching. The method has higher demodulation accuracy. ZPW-2000 frequency shift signals of which sampling duration is greater than or equal to 0.11s in a high-signal-noise-ratio environment can all be correctly demodulated by the method. At the same time, the method has real-time demodulation capability, better white noise resistance capabilityand better single-frequency interference resistance capability.

Description

technical field [0001] The invention belongs to the field of railway signal track circuits, and relates to a ZPW-2000 signal demodulation method based on nonlinear least squares method, which is applied to ZPW-2000 track circuits in trains with ordinary speed and equipped with CTCS-2 train control system. Demodulation of frequency-shifted signals. Background technique [0002] ZPW-2000 track circuit, as a kind of ground-car uninterrupted communication equipment, is widely used in my country's existing lines and passenger dedicated lines. In the ZPW-2000 track circuit section, the vehicle TCR (track circuit reader) antenna continuously senses that the rail is used as the transmission The ZPW-2000 frequency-shifting signal of the medium, the on-board equipment uses the sampling value of the induced voltage to demodulate to obtain the low-frequency code sequence, so as to know the occupancy of the section ahead and guide the safe operation of the train. [0003] Since the ZPW-2...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04L27/14H04L27/10H04L27/00
CPCH04L27/0014H04L27/10H04L27/14
Inventor 武晓春戈壁舟
Owner LANZHOU JIAOTONG UNIV
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