说明：  基于超声波检测的倒车雷达设计 其原理为:在超声波发射器两端输入10个40kHz脉冲串，脉冲电信号经过超声波内部振子，振荡出机械波，通过空气，介质传播到被测面，由被测面反射，超声波接收器接收
(Based on ultrasonic testing of reversing radar design The principle is: In the ultrasonic transmitter at both ends of input 10 40kHz pulse train, pulse ultrasonic signals through the internal oscillator, a mechanical wave oscillation, through the air, medium spread to the measured surface from the measured surface reflection, ultrasonic receiver to receive)