Multi-Frequency Ultrasonic Sensors with Locally Distributed Resonators

Ultrasonic sensors are widely used in automotive applications for surround sensing. A rising number of applications in the field of highly automated and autonomous driving require a more detailed surround sensing performance. This results in an increasing number of applied ultrasonic sensors. To operate a higher number of sensors in parallel or in shorter intervals, it is desired to conduct measurements with two different frequencies to discriminate the sensor signals. Known multi-frequency ultrasonic sensors often use multiple spatial separated electro-mechanical transducer elements to realize different working frequencies. Realizing a multi-frequency ultrasonic sensor with only one electro-mechanical transducer element is less examined in literature. This study investigates how to modify the operational deflection shape in order to obtain two resonance frequencies with similar and appropriate sound radiation. This is done in a generic model for a plate-like structure by modifying the operational deflection shape using locally distributed resonators. In finite element simulation, different resonator configurations are studied. Furthermore, it is investigated whether the effect is caused by resonant behavior or by added mass of the resonators. The results show that locally distributed resonators are a suitable solution to modify the operational deflection shape of a plate-like structure in order to obtain two deflection shapes with similar sound radiation. Based on the investigation, a multi-frequency ultrasonic sensor can be realized with only one electro-mechanical transducer element.