Multicarrier airborne ultrasound transmission with piezoelectric transducers

Abstract

In decentralized localization systems, the received signal has to be assigned to the sender. Therefore, longrange airborne ultrasound communication enables the transmission of an identifier of the sender within the ultrasound signal to the receiver. Further, in areas with high electromagnetic noise or electromagnetic free areas, ultrasound communication is an alternative. Using code division multiple access (CDMA) to transmit data is ineffective in rooms due to high echo amplitudes. Further, piezoelectric transducers generate a narrow-band ultrasound signal, which limits the data rate. This work shows the use of multiple carrier frequencies in orthogonal frequency division multiplex (OFDM) and differential quadrature phase shift keying modulation with narrowband piezoelectric devices to achieve a packet length of 2.1 ms. Moreover, the adapted channel coding increases data rate by correcting transmission errors. As a result, a 2-carrier ultrasound transmission system on an embedded system achieves a data rate of approximately 5.7 kBaud. Within the presented work, a transmission range up to 18 m with a packet error rate (PER) of 13% at 10-V supply voltage is reported. In addition, the transmission works up to 22 m with a PER of 85%. Moreover, this paper shows the accuracy of the frame synchronization over the distance. Consequently, the system achieves a standard deviation of 14 μs for ranges up to 10 m.

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“…where f 0 = 40 kHz is the resonance frequency of the transducers. In order to obtain the unfocused beamforming vector, in (8) ∆t foc,m is replaced with ∆t foc,m . Subsequently, the spatially filtered analytic spectrum is transformed back into the time domain using IFFT and its envelope is generated by forming the absolute value of each element, that is…”

An Ultrasonic Object Detection Applying the ID Based on Spread Spectrum Technique for a Vehicle

“…However, there is only one chirp pattern, and it cannot be used for indoor ranging systems that need to distinguish multiple sensors. A. Ens and L. M. Reindl [9] applied orthogonal frequency division multiplexing (OFDM) to the ranging system used for localization. This scheme uses multiple subcarrier for transmission, improving the data transmission efficiency and reducing the length of the transmitted wave.…”

“…This scheme uses multiple subcarrier for transmission, improving the data transmission efficiency and reducing the length of the transmitted wave. However, orthogonal frequency division multiple access (OFDMA) is not applied because subcarriers on the transducer in [9] are too narrow to divide into multiple groups.…”