回波延时  echo delay

长延时回声消除  long time delay echo cancellation

超声波回波测距  ultrasonic wave echo measuring distance

超音波回波图  ultrasonic echogram

迟延回波  delayed echo

海面回波波谱  Spectra of ocean return signal

回波波形  Echo waveform

回波时间  echo time

回波时间预估  Time-estimating of arrival

回波时移  Echo shifts

回波延迟  echo delay

连续波回波信号  contiuous-wave echo signal

脉冲回波波形分析  Laser echo waveform analysis

森林回波波形  waveform from forests

声波回波  sound echo

光波延时  light wave retardation

脉波延时  pulse duration

脉波延时调变  pulse duration modulation

天波时延  sky wave delay; sky-wave delay