3-D Ultrasonic Sensing in Air with a Narrowband Transmitter and a Receiver Microphone Array

This paper leverages phased array techniques to determine the positions of multiple reflectors in 3-D space using ultrasonic sensing. The design of a low-cost sensor, consisting of a single narrowband ultrasonic transducer and a receiver array consisting of a small number of MEMS microphones, is discussed. Aspects of system design related to the sensor, analog signal chain, and digital processing are presented. A processing algorithm is described to simultaneously determine the 3-D positions of all the reflectors present in the sensor’s workspace. Further, the processing algorithm is implemented on a low-cost microcontroller and requires low memory resources (64-70 kilobytes). Experiments demonstrate the performance achieved and the detection of multiple objects in the sensor’s workspace. A computation cost analysis is performed exhibiting the rapid execution of the algorithm. High processing throughput (20-45 Hz) is achieved making the sensor suitable for applications such as workspace mapping and the tracking of multiple reflectors.