A robust doppler ultrasonic 3D imaging system with MEMS microphone array and configurable processor

In ultrasonic imaging, the Doppler effect, which is caused by the movement of the target, causes a frequency shift on the reflected sound, and results in object detection failure. We have constructed an experimental system for ultrasonic imaging. By utilizing a log-step multicarrier signal as the transmitter wave, we succeeded in obtaining 3D imaging of a moving object. The system comprises of a number of MEMS sensors and an FPGA configured to capture signals from the sensors and store them in the memory device for sufficient duration. We show the imaging results using a log-step multicarrier signal as well as using a traditional log-swept chirp signal and a linear-step multicarrier signal. The results exemplify the possibility of Doppler 3D imaging using the system, and the validity of log-step multicarrier signals.