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时频分布作为现代信号处理研究的热点,它能同时描述信号在频率域和时间域内变化。移频轨道电路信号是一种相位连续的移频键控(FSK)信号,它的载频和低频信息通过FFT可以很容易的检测出来,但上下边频的高精度检测,一直是比较棘手的问题。本文提出了一种基于时频分布的FSK信号的解调方法,这种方法可以克服单一时域或频域FSK信号解调时的缺点,实现对FSK信号的上下边频的可靠、高精度的解调。文中对FSK信号的WVD、PWVD和SPWVD结果作了比较,选择了基于SPWVD来估计FSK信号的上下边频,并给出了具体的算法步骤。计算机仿真表明,采用SPWVD可准确地解调出移频信号的上下边频,与FFT相结合,可实现移频信号的完整解调。这为研制高精度的FSK信号检测仪器奠定了理论基础。
As a hotspot in the field of modern signal processing, time-frequency distribution can simultaneously describe the signal changes in the frequency domain and time domain. Frequency-shift track circuit signal is a phase-continuous frequency shift keying (FSK) signal whose carrier frequency and low-frequency information can be easily detected by FFT. However, it is always tricky to detect the upper and lower side frequency accurately problem. This paper presents a time-frequency distribution based on the FSK signal demodulation method, this method can overcome the single time-domain or frequency domain demodulation of FSK shortcomings, to achieve FSK signal up and down frequency of reliable, high-precision demodulation. In this paper, the WVD, PWVD and SPWVD results of the FSK signal are compared, the upper and lower side frequency of the FSK signal is selected based on the SPWVD, and the specific algorithm steps are given. Computer simulation shows that the use of SPWVD can accurately demodulate the frequency of the signal shifted up and down, combined with the FFT, the frequency shift can be achieved complete demodulation. This laid the theoretical foundation for the development of high-precision FSK signal detection instruments.