首先讨论了舰船辐射噪声的产生机理、构成和频率特性，指出螺旋桨噪声的振幅存在周期性调制。

First, the generation mechanism, components and frequency characteristic of radiated noise of naval ships are studied. There exists periodical modulation for the amplitude of propeller noise.

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对载波中的信息进行压缩的编码方式可以是载波或周期的频率调制或振幅调制。

The coding used to impress information on the wave can be a function of the frequency (the number of waves or cycles per second) or amplitude of the waves or cycles.

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因此，若将重复周期参差调制方式融合到频率编码信号中，可使信号具备时-频调制双重随机性。

So, the modulation of irregular pulse repetition interval may be employed in FCP that the randomization of signal modulation would be obtained in both time and frequency domains.

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