Improved Ultrasonic Phased Array Based on Encoded Transmissions for Obstacle Detection

In this paper, a new signal processing algorithm for ultrasonic sensory systems in airborne transmission is presented. The proposal is based on a phased array (PA) where the excitation signals are loosely synchronous (LS) sequences, often used in code division multiple access communication systems. Hence, by setting a different LS sequence for each steering angle, it is possible to simultaneously acquire all the information of the scanned area with a single fire, in order to detect possible reflectors in front of the sensory array. The use of these LS sequences combined with PA techniques allows to simultaneously steer the main beam in different directions with low interference. Simulation results reveal that this approach does not only provide longer distance inspection, but also noise robustness. Furthermore, this algorithm provides higher image rate than conventional PA techniques even for high-quality images, since the image rate does not depend on the number of steering angles to be explored.