Design And Implementation Of FPGA-Based Six-Channel Non-Crosstalk Sonar System

In order to solve the common defects of traditional sonar systems, includinginterference among transducers (i.e. crosstalk) and low accuracy, this thesisintroduces the design and implementation of a field programmable gate array(FPGA)-based six-channel non-crosstalk sonar system.In the non-crosstalk sonar system, the pulse compression technique is applied inthe ultrasonic transducer excitation and receiving process. Gold sequence combinedwith binary frequency shift keying modulation, owing to the outstandingcomprehensive performances in both correlation and energy characteristics after theassessment of different codes and modulations’ combination, is chosen as theexcitation sequence. Meanwhile, correlation-matching method is used to identify theecho of the transmitted ultrasound. To reduce the correlation computation’scomplexity and save the hardware resources, the system adopts cross-zero polaritycorrelation method to process the echo signal and to capture the time-of-flight (TOF)of ultrasound.A six-channel ultrasonic ranging hardware platform is designed, in which everytransducer acts as both transmitter and receiver. Based on the platform, the sonarsystem uses the FPGA chip to control the emission and receiving of thecode-modulation sequences as well as to achieve the ranging results, using thecross-zero polarity correlation method. Finite state machine and flow line are appliedto make the most of the FPGA’s storage and speed up the computation.Experiments are conducted with6SensComp600series electrostatic transducers.Results show that this sonar system achieves an accuracy of15mm in the rangebetween20cm and6m without crosstalk. The designed six-channel non-crosstalksonar system could be applied to assist robot navigate in identifying360°environmentinformation.