Digital-signal-processing techniques for the design of coded excitation sonar ranging systems

The subject of the authors' investigation in this paper concerns how an in-air sonar sensor using correlation techniques can distinguish its own emissions from the emissions of other sonar sensors. Because of the limitations in the time-bandwidth products of transmit signals that can be used with narrowband sonar sensors, coded excitation ranging systems based on the classical theory of pseudorandom or random signals cannot achieve in practice high degrees of rejection between the different emissions. The method the authors present in this paper allows for designing pairs of coded transmit signals with high degrees of rejection, while the high accuracy and good spatial resolution of correlator-based range measurements are retained. The experimental verification of the method is carried out using high-frequency piezoelectric sensors.