Theoretical Research On Signal Generator And Transmitting And Receiving Circuits Implementation Of Parametric Sub-bottom Profiler

As the development of science research, parametric array sonar based on nonlinear acoustics has been widely used in engineering domain internal and abroad. In this thesis, transmitting and receiving techniques of sub-bottom profiler based on parametric array have been studied, the main work as follows:The first part is about theory. On the basis of the theory of nonlinear acoustics, the theory which makes parametric array generating difference frequency is discussed, then, difference frequency directivity and beam width of parametric array are analyzed, while the relation among them and primary frequency is analyzed. The directivity of primary frequency and difference frequency are simulated by MATLAB software; in addition, gain of the difference frequency of parametric array is analyzed.Then, based on parametric array of double primary frequencies, the wide-band parametric array is studied from the point of waveform design. Its difference frequency gain is analyzed. The difference frequency signals which are formed by several different transmitting signals are simulated. And rotating directional transmission of signal is analyzed theoretically and simulated.In the second part, the design of the hardware circuit of signal source is described. In allusion to the require of wide-band parametric array's primary wave signal and multi-beam, the signal source circuit, whose core is DSP and which use CPLD to control logic circuits, is designed and implemented. The interfaces which communicate with host computer and keep synchronization with other devices are obligated; in allusion to difference frequency signal, based on vector sonar, the four channels receiver, which has function with changing difference signal into non-difference signal, magnifying, filtering and auto gain control is designed and implemented.In the last part, the software algorithm is described. The idea of signal source's programmed algorithm and the program block diagram of transmitting which is real-time are introduced. The algorithm is implemented by assemble language. The algorithm is real-time implemented on the hardware circuit of signal source using the CCS debugger and emulator.