Time of Flight Capture in Spread Spectrum Method for Ultrasonic Distance Measurement

Based on the research on digital correlator and spread spectrum technology used in radar system,a method of time of flight(tof) capture in spread spectrum method for ultrasonic distance measurement is proposed.An appropriate pseudo random number is modulated by ultrasonic sensor and transmitted.The time of flight can be got by using digital correlation approach to find the phase difference between transmitting sequence and receiving sequence.The correlation function is computed by parallel digital correlation technology using XOR and addition operation taking place of FFT algorithm using multiplication.This method shortens the processing time and FPGA resource.The system design is based on Aletra's quartusⅡsoftware,and fitted to FPGA chip after logic synthesizing and placement routing.The timing simulation results in placement and routing is also presented.