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 obser

实现stft变换，输出时域图，频域图，能量谱等信号分析图。-Stft achieve transformation, the output time domain diagram, frequency domain, the energy spectrum and other signal analysis chart.