非平稳信号泛指具有时变能量谱的确定性信号和具有时变功率谱的随机信号。幅度调制是非平稳性的一种表现形式。调幅信号分析主要任务之一是提取幅度随时间变化的规律。在希尔伯特变换平方解调方法的基础上，提出了利用适用于非平稳信号的希尔伯特变换低通滤波器，提取调幅信号的包络，实现非平稳调幅信号的分解。数值算例验证了方法的有效性。

Non-stationary signals generally refer to deterministic signals with time-variant energy spectrum or stochastic signals with time-variant power spectrum. Amplitude modulation is one of the forms of non-stationarities. The main objective of amplitude modulated signal analysis is to obtain the rule of amplitude variation. Based on the Hilbert square demodulation method and the “Hilbert Lowpass Filter” suitable for non-stationary signal recently discovered, the envelop is extracted from an amplitude modulated non-stationary signal. Numerical examples are given to illustrate the efficiency of this method.