Test system of laser ultrasonic directional transmission channel characteristics

摘要

In order to enhance the transmission efficiency of laser ultrasonic signal and realize laser ultrasonic directional transmission, a channel characteristic test system based on double sliding window algorithm is designed in this paper. This paper analyzes the principle of laser ultrasonic directional transmission, selects the double-sided band modulation mode, and obtains the differential frequency wave sound pressure generated by the nonlinear interaction according to the Lighthill sound scattering principle; obtains the laser ultrasonic directional transmission efficiency parameters by calculating the differential frequency sound intensity after the air nonlinear interaction, and creates the preconditions for the construction of the system; and through the channel impulse response detection algorithm.The CIR vector is obtained by using the local PN sequence and the peak value generated by the received signal, the threshold value is determined based on the double sliding window algorithm, the end position of the interval is determined, the accuracy of channel estimation is improved, and the error code performance of the system is improved; the full digital DQPSK is demodulated by using FPGA and DSP devices, and the channel characteristic test system is constructed by using the analog-to-digital conversion plate and the interface plate. The simulation results show that the designed system can effectively improve the transmission accuracy of the laser ultrasonic audio channel, and the system has a high efficiency of data reception, strong practicability and robustness.