信号与线性系统的时频域分析：观测已知方波信号、正弦波信号的频谱；观测实时模拟信号的频谱；加深理解时域周期信号的各频率分量在振幅频谱图上所占的比重；观测相位在波形合成中的作用；LTI系统的频域分析，LTI系统对周期性输入信号的响应。-Signals and linear systems with time-frequency domain analysis: observation known square wave signal, sine wave signal spectrum　observation of the spectrum in real-time analog signal　a deeper understanding of time-domain periodic signal component in the amplitude of each frequency spectrum chart the proportion of　 observation phase in the waveform synthesis　LTI system frequency domain analysis, LTI system response to periodic input signals.