摘要
多普勒效应是发射机与接收机相对运动时，接收讯号频率fg对发射讯号频率fT产生频偏fd的现象，频偏大小与两者相对速度v成正比，即：
This article details an efficient method applied on the principle of Doppler effect to fish detection and navigation instruments-color current indicator,electronic scanning sonar,satelite navigator,etc.
