富里叶变换 PW PW Transmitter Receiver Pw PW=10~50uS T=4s Freq range 2 Pl =200,000-400,000Hz 7=4=0.25Hz 2021/2/202021/2/20 富里叶变换 Pw 1  T 1 T PW PW Transmitter Receiver PW=10~50μs T=4s Freq.range P W 1 2 =200,000~400,000Hz T 1 =4 1 =0.25Hz