Sharpening directivity of ultrasonic range sensor using multiple transmitters by different amplitude and pulse width method

It is necessary to increase detectable length of ultrasonic range sensor for autonomous land vehicles. This means that we must radiate the powerful ultrasonic waves whose directivity is sharp. However sound waves have the characteristic that small attenuation in propagation and sharp directivity are incompatible with each other. In order to decrease attenuation rate for distance, the authors used multiple ultrasonic transmitters whose frequency is 40 kHz although their directivities are not sharp. We tried to sharpen the directivity by using plural transmitters and by exciting multiple transmitters whose individual outputs are different from each other. This paper describes how to get sharp directivity by ultrasonic transmitters array and its design method. The effectiveness is confirmed by simulations and experiments.