How to synchronize the signal is a core issue in discrete short-time Fourier transform (DSTFT) demodulation algorithm for FSK signal. A new synchronous algorithm based on spectrum was proposed by analyzing and comparing the specific relationship between spectrum of 2FSK signal and code shifting, which divides the whole signal reception process into two parts-the capturing process and the tracking process, and different synchronous algorithm is adopted for different process. MATLAB simulation indicates that the character error rate is much lower than one of the other synchronous algorithms when the signal-noise ratio is comparative. Meanwhile, the synchronous algorithm has been used in actual NAVTEX receiver, the sensitivity of which meets the testing standards of NAVTEX: the character error rate is below 4% when the intensity of input signal is -107 dBm, and the receiver successfully received and demodulated the information of international channel.%针对FSK调制信号在离散短时傅里叶变换(DSTFT)解调算法中的同步问题,通过分析比较2FSK信号的谱图与码元偏移之间的特定关系,提出一种基于谱图的同步新算法,即将信号接收过程分为码元起始点捕获过程和码元跟踪过程,针对不同的接收过程采用不同的同步算法.MATLAB仿真结果表明:在相同信噪比的情况下,采用基于谱图的同步算法比其他同步算法解调的误码率更低.该同步算法已用于实际的NAVTEX接收机中,接收灵敏度满足NAVTEX检测标准:当输入信号强度为-107 dBm时,误码率小于4％,并且接收机已成功接收、解调出国际通道信息.
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