说明：  多普勒计程仪作为一种导航仪器出现并发展了很长时间，但是传统的声 学多普勒导航仪使用的还是简单的窄带信号，由于窄带信号时间带宽积没有 增益，
(Doppler log as a navigational instrument appeared and developed for a long time, but the traditional sound Simple narrowband signals are still used in Doppler Navigator because the time-bandwidth product of narrowband signals is not available. Gain, which enables traditional DVL to measure velocity accurately, range resolution, operating distance and velocity.)