Sonar equipments are widely used. Its application in the military and civilian promotes the research and development of sonar technology. It is a research focus of sonar technology to increase sonar effective range. As so far, it limits the increasing of sonar effective range by various reasons. By using the nonlinear propagation effect in medium, parametric acoustic array theory can produce sound with high directivity. The sound spread a long distance because of its low frequency. Besides, the size of launch array is not much big because of the high frequency of the original ultrasonic wave. The advantages of parametric acoustic array can be used effectively in active sonar system. It can increase sonar effective range and its resolution.This article focuses on the combination of parametric array and the signal of active sonar. The influence mechanism of DSB modulation algorithm and SSB modulation algorithm to CW signal and LFM signal is analyzed. The form of produced sound can be discussed by using the Berktay equation. By researching the frequency domain characteristics and the time domain characteristics of the produced sound, some feasible combination of several parametric array transmit waveform and modulation techniques are discussed.The results show that DSB modulation algorithm and full carrier SSB modulation algorithm can be applied to parametric array sonar. Full carrier modulation algorithm will generate harmonics of which the frequency is twice of the input signal. Low modulation index can be helpful to reduce harmonic distortion. As a result, the amplitude of the valid signal is also reduced. The frequency of produced sound is single if using carrier suppressed DSB modulation algorithm. The produced sound can be used as parametric array transmit waveform.Phased launch technology is an important research content of active sonar. By researching of the control of emitting beam, a design method of transmission array is proposed. The transmission array of parametric sonar is designed. The plane array is designed to a 5*15 rectangle array. There are 15 rows in horizontal direction and 5 lines in vertical direction. The horizontal directional angel is 3.8 degree and the vertical directional angel is 13.1 degree. The direction control method of parametric sonar is researched. By using time-delay beamforming technology, the directional transmission of signal is realized.A hardware processing platform based on FPGA is developed. The signal processing algorithms of parametric sonar are verified which include designing of transmission wave, modulation algorithm and time-delay beamforming technology. An experimental platform is built in the muffler pool. By analyzing the received wave, the feasibility of parametric sonar is verified. And all the algorithms proposed are verified. |