| High frequency sonar transducers and arrays are devices that transmit and receive high frequency acoustic waves,and are the key core of high frequency sonar systems.They have the characteristics of high frequency operation,small size,compact structure,and complex technology.Common high-frequency sonar transducers and arrays include planar transducers,arc transducer arrays,linear transducer arrays,cylindrical transducer arrays,and spherical cap transducer arrays.Currently,high-frequency sonar transducers and arrays face technical challenges such as easy coupling of vibration modes,bandwidth to be broadened,large directional fluctuations,and complex outgoing lines of multi-channel receiving array elements.With the support of projects such as the National Natural Science Foundation of China and the Shanghai Municipal Natural Science Foundation,this paper conducts research on key manufacturing technologies such as high-frequency sonar transducers and arrays’ vibration mode decoupling,broadband response,directional optimization of multibeam transducers,and integration of receiving array elements and preamplifiers.It aims to improve the electroacoustic performance of high-frequency sonar transducers and arrays,and optimize manufacturing processes,Provide a new method for the design and fabrication of highperformance high-quality high-frequency sonar transducers,and provide technical support for the development of high-frequency sonar such as high-frequency multibeam bathymetric sonar,image sonar,and so on.Firstly,aiming at the decoupling technology of high-frequency vibration modes,the thesis carried out theoretical research on the thickness vibration of piezoelectric discs,simulated the thickness vibration modes of piezoelectric discs,calculated the thickness vibration frequencies,higher order radial vibration frequencies,and various coupling vibration frequencies,and clarified the coupling effect of radial higher order frequencies on the thickness vibration frequencies.This paper proposes a method to reduce the influence of radial higher order modes on thickness vibration modes by adjusting the size of the center hole to decouple the radial higher order modes.For the decoupling of rectangular array elements of high-frequency sonar receiving transducers,the paper reduces the coupling effect on the thickness vibration modes by adjusting the width size or fine tuning the length size of the rectangular bar to make the higher-order vibration frequency of the length far away from the thickness vibration frequency.The paper also studied the coupling vibration of large anisotropic piezoelectric ceramics,explored the coupling effect characteristics of large anisotropic piezoelectric materials,developed a low coupling high frequency sonar transducer with large anisotropic piezoelectric ceramics,and conducted experimental verification.The results show that the method of size adjustment has a decoupling effect on the thickness vibration of high-frequency transducers,which can improve the emission ability of circular plate transducers,improve the directivity of high-frequency sonar receiving arrays,and utilize the anisotropy of piezoelectric materials to reduce the impact of lateral coupling of low-voltage electrical oscillators on the thickness vibration modes,thereby optimizing the manufacturing process of high-frequency transducers.Secondly,aiming at the broadband response technology of high-frequency sonar,the thesis has carried out research on piezoelectric composite broadband technology,matching layer broadband technology,acoustic impedance gradient matching layer technology,and backing broadband technology.The effects of the aspect ratio of piezoelectric ceramic particles and the material parameters of the polymer in the cutting gap on the broadband performance of the transducer were studied and analyzed.The matching layer 1-3 piezoelectric composite ceramic volume ratio was optimized,and the matching layer 1-3 piezoelectric composite transducer was fabricated.The transmission voltage response bandwidth of the transducer was tested,and the test data showed that the bandwidth was greater than 50%.For the acoustic impedance gradient matching layer technology,the paper introduces the manufacturing process of the acoustic impedance gradient matching layer in detail.The matching layer mold is made using 3D printing technology,and the equivalent gradient change of acoustic impedance is achieved by filling a hollow cone material with a fluid mixture.In this paper,an acoustic impedance gradient matching layer was developed,and the acoustic impedance parameters of the gradient matching layer material were tested.A high-frequency broadband transducer with a bandwidth greater than 110% was fabricated.For the backing bandwidth technology,the paper proposes a preparation device for producing an acoustic backing material.Using this device,an acoustic backing material was fabricated,and the acoustic attenuation coefficient of the backing material was measured,with an average attenuation of about 9 d B/cm.A broadband acoustic backing transducer was fabricated,and the transmission voltage response of the transducer was tested.The test data showed that the bandwidth was greater than 10%.Thirdly,aiming at the directivity optimization technology of high-frequency sonar transducer arrays,the acoustic materials,array structure,and manufacturing process are studied around the arc emitting transducer array,with emphasis on important parameters such as operating frequency,radius of curvature,the center angle corresponding to the emitted ceramic particles,and the directivity fluctuations within the horizontal beam range,as well as their mutual constraints.This paper proposes an arc-shaped array scheme for arranging piezoelectric ceramic particles along an ellipse.By adjusting the spacing of ceramic particles in the arcshaped emission transducer array,the spikes on the horizontal directional edge can be reduced,and the beam fluctuation can be reduced.The horizontal directional fluctuation can be reduced from 6 d B to less than 3 d B,and the transmission voltage response level of the arc-shaped emission transducer array can also be improved.For the directivity of the receiving array,the amplitude consistency,spacing,sound barrier plates,boundary conditions,and other factors between the array elements have an important impact on the directivity of the array element.This paper uses the sound barrier plate method to expand the directivity angle of a single array element.Through comprehensive design and optimization of various parameters,it can effectively achieve a horizontal beam angle of the array element greater than 120 °,making the beam angle meet the requirements of a wide beam scanning range of high-frequency sonar.Finally,aiming at the integrated manufacturing technology of receiving array elements and preamplifier circuits,the thesis has carried out the optimization of receiving sensitivity of high-frequency receiving array elements,the development of preamplifier circuits,and the integrated manufacturing of receiving array elements and preamplifier circuits.The optimization of the electro-acoustic performance of the array elements is carried out through theoretical calculation and simulation.The voltage reception sensitivity of the array elements of different piezoelectric materials is compared.The sidelobe level is simulated and analyzed using finite element software.Based on the simulation results,a prototype transducer is developed and its underwater performance is tested.The test data show that the difference in voltage reception sensitivity of different piezoelectric materials at the anti resonance point is smaller than the difference in low frequency voltage reception sensitivity.The paper also studied and manufactured a preamplifier circuit,and tested its circuit power consumption,input impedance,signal bandwidth,signal waveform,channel consistency,etc.The test results show that the single channel circuit has a power consumption of about 0.02 W,an input resistance of about 100 k Ω,a gain of 20 d B,and an amplitude uniformity relative error of less than ± 0.4%.The preamplifier circuit is suitable for matching and amplification with high-frequency sonar receiving transducer arrays.In this paper,the preamplifier circuit is integrated with the receiving array element to shorten the signal lead-out line of the array element.The input of the preamplifier circuit corresponds to the output number of the array element one by one,solving the technical problem of complex lead-out lines and loss of output signal-to-noise ratio caused by the number of channels in the receiving array element,optimizing the manufacturing process of the receiving transducer array,and improving production efficiency.In this paper,an integrated prototype of high-frequency sonar receiving transducer array has been fabricated,and the reception sensitivity level of the single channel array element tested is about-193 d B,fully meeting the overall performance requirements of high-frequency sonar. |
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