The character of FSK spectrum is centrosymmetric, spectrum peaks spread with an interval of the modulation frequency, so the right frequency cannot be got by FFT spectrum.

• 移频信号的频谱特性是谱峰以新出现的边频频率为中心，以低频频率为间隔向两边展开，通过FFT谱分析不能得到精确的结果；