Research On The Method Of Waveform Control In Parametric Array Of Transient Signals

It has been more than fifty years when parametric array was fround. It has beenconcerned and used in sub-bottom profiler because of its excellence, such as "small size, wideband, narrow beam, no side lobe". But it have not used in underwater acousticcommunications. The reason is that the secondary waveform is difficulty to control, besidesthe low efficiency of parametric array. so we need to find a way to control the waveform ofsecondary wave in parametric array of transient signals.Based on Moffett’s theory of parametric array of transient signals, this article derives theacoustic field distribution along the acoustic axis direction of the parameter array. Firstly,research on the phase relationship between the difference signal with the primary signal alongthe acoustic axis at a certain point. According to this relationship,we put forward one methodof phase control of secondary wave. Secondly, we calculated the waveform of secondarywave respectively when the envelope of the primary signals are gaussian pulse signal, chirpsignal or gaussian pulse chirp signal. In order to get the second signal which is one of themost common sonar signal, we pretreated the primary signals in theory to achieve the purposeof waveform control of secondary wave.According to the theory in this paper, the computer programme can be written by Matlab.Simulated the waveform of secondary wave, and designed for the excitation signal of primarywave.The experiments on parametric array theory were carried out in the sink. Finally, we gotthe secondary wave which we want. Experimental results coincide well with theoreticalcalculation.