Real-Time Noncrosstalk Sonar System by Short Optimized Pulse-Position Modulation Sequences

Ultrasonic crosstalk is one of the main causes of false distance measurements that reduce the work efficiency of sonar sensors in mobile robots. To enhance the real-time performance of sonar systems, short digital pulse-position modulation (PPM) sequences are used to trigger ultrasonic transducers. Due to their properties of sharp autocorrelation and flat cross correlation, chaotic and pseudorandom number series are used to modulate pulse positions. A genetic algorithm is adopted to optimize the range of duration between pulses. Real experiments using Polaroid 600 series instrument-grade electrostatic transducers validate the suitability of the proposed method.