Ultrasonic Distance Measurement Used On Pseudorandom Code

The ultrasonic distance measurement is a kind of tecnique that is not to get in touch with the object,which is make use of the ultrasonic's directional spreading and solid reflectiong characteristic in the air,via receiving the oneself blast-off ultrasonic reflecting signal, according to time difference between ultrasonic sending and receiving and spreading speed , computing to spread the distance, so getting the object's distance.Along with the ultrasonic range finder is widely applied in the daily life, people gradually discovers these range finders exsitting serious blemish:(l) Valid function distance is short, but depending on increasing the blast-off power to increase it is very limited;(2) The measurement distance's accuracy primarily is decided by the Signal-to-Noise of the echo signal.At the certain Signal-to-Noise, only depending on increasing the ex-class enlarge electrocircuit's plus to improve measure accuracy is very limited. In order to solve the above problems, we develop ultrasonic range-finder which is based on pseudorandom code.Pseudorandom binary sequence PRBS(also called pseudorandom binary signal) is a row of period binary sequence.lt has the same characteristic with white noise. The longest shift register sequence(m sequence) is a kind of PRBS, its self- correlation function is similar to the pulse function.lt accords with the measure distance code's necessary condition, especially with a long period PRBS ,we can obtain two purposes which are overcoming the measuredistance mistiness and realizing the well accuracy.PRBS is applied in ultrasonic distance measurement in this article, which resolves some problems existing in it. We are researching more theories of PRBS,and sufficiency exerting the virtue of PRBS and DSP,and integrating software with hardware,then appling them to manufacture,and improving ultrasonic distance measurement system's accuracy from 1cm to 0.5cm, and the distance from 10m to 22m.