For anti-jamming and anti-countermeasure techniques of the sonar receiver, the response characteristics of the automatic gain control （AGC） circuit and the survivability of the prime circuit under strong interferenc...For anti-jamming and anti-countermeasure techniques of the sonar receiver, the response characteristics of the automatic gain control （AGC） circuit and the survivability of the prime circuit under strong interference are analyzed by simulations and experiments. An AGC simulation model based on the voltage control amplifier VCA810 prototype is proposed. Then static and dynamic simulations are realized with single frequency signal and linear frequency modulated （LFM） signal commonly used in the active sonar. Based on intense sound pulse （ISP） interference experiments, the real-time response characteristics of each module of the receiver are studied to verify the correctness of the model as well as the simulation results. Simulation and experiment results show that, under 252 dB/20 μs ISP interference, the specific sonar receiver will produce sustained cut top oscillation above 30 ms, which may affect the receiver and block the regular sonar signal.展开更多
It is an efficient method to model ship radiated noise as quasi-periodic random sound pulse sequences. Based on the model, this paper discusses the characteristics change of ship noise after through shallow-water wave...It is an efficient method to model ship radiated noise as quasi-periodic random sound pulse sequences. Based on the model, this paper discusses the characteristics change of ship noise after through shallow-water waveguides. Theoretical analysis and numerical simulation show that random waveguides and multi-path effects can bring much additional transmission loss for the noise line spectra, demonstrating the instability of ship radiated noise line spectra to a certain extent, and providing some theoretical support for advanced studies of ship radiated noise.展开更多
A sound pulse scattering from an edge of thick plates is experimentally and numerically investigated. Beside the edge diffracted signal, waves radiated by the plate that are excited from the plate edge are also detect...A sound pulse scattering from an edge of thick plates is experimentally and numerically investigated. Beside the edge diffracted signal, waves radiated by the plate that are excited from the plate edge are also detected in the diffraction process. The phenomena are examined by the elastic plate theory and agrecment is observed. The finite difference method (FDM) is used in the numerical calculation. Field distribution around the plate edge and fields at certain points as functions of time are displayed. Comparison is made with experiments. It is found that the grid size of FDM formulation may affect accuracy of computation significantly, but the results show the same phenomena as that measured in experiments.展开更多
This paper presents a method to control the gain within pulse and accurately measure the amplitude of an underwater sound pulse in a wide dynamic range. In the method a loop composed of a gain controlled unit and a mi...This paper presents a method to control the gain within pulse and accurately measure the amplitude of an underwater sound pulse in a wide dynamic range. In the method a loop composed of a gain controlled unit and a microcomputer is employed.This method also gives satisfactory results when there exist distortion of signal cnvelop and fluctuation of signal amplitude. The basic mathematical model of instantaneous amplitude-gain control and amplitude measurement and its hardware structure are presented. The calibration method of the system for retransmitting (responding) with required sound level is given as well.展开更多
Detachment size determination with an acoustic method has been carried out for two interacting bubble plumes formed at neighboring needles in quiescent water. Two sets of needle pairs, one with 1.5mm and 0.8mm inner d...Detachment size determination with an acoustic method has been carried out for two interacting bubble plumes formed at neighboring needles in quiescent water. Two sets of needle pairs, one with 1.5mm and 0.8mm inner diameters and the other with the equal 1.5mm inner diameters, were separately used as the bubble pair injectors in the experiments. Consequently, four typical patterns of bubble plumes interaction could be observed in the two cases of needle pair matches. Through measuring the pressure pulses radiated by the bubble pairs immediately after their 'pinching-off ' and by making use of a sophisticated relation between oscillation frequency of volume mode and radius of gas bubble, the detachment size of the bubble plumes have been determined from the amplitude/frequency spectrum of the sound pressure pulses. The experimental results demonstrate that the acoustical method is valid in both of the interacting and non-interacting circumstances in bubble field and the bubble size measurements by this acoustical method agree well with the measurements from photographic analysis. Finally, a comparison has been made on the strong and weak points of the acoustical method with the other size determination methods.展开更多
基金supported by the National Natural Science Foundation of China (10974154)the National Innovation Project of China for Undergraduates (101069935)
文摘For anti-jamming and anti-countermeasure techniques of the sonar receiver, the response characteristics of the automatic gain control （AGC） circuit and the survivability of the prime circuit under strong interference are analyzed by simulations and experiments. An AGC simulation model based on the voltage control amplifier VCA810 prototype is proposed. Then static and dynamic simulations are realized with single frequency signal and linear frequency modulated （LFM） signal commonly used in the active sonar. Based on intense sound pulse （ISP） interference experiments, the real-time response characteristics of each module of the receiver are studied to verify the correctness of the model as well as the simulation results. Simulation and experiment results show that, under 252 dB/20 μs ISP interference, the specific sonar receiver will produce sustained cut top oscillation above 30 ms, which may affect the receiver and block the regular sonar signal.
基金supported by the National Natural Science Foundation of China(11174314,11474301,11204345)the State Key Laboratory of Acoustics,Chinese Academy of Sciences(SKLA201502)
文摘It is an efficient method to model ship radiated noise as quasi-periodic random sound pulse sequences. Based on the model, this paper discusses the characteristics change of ship noise after through shallow-water waveguides. Theoretical analysis and numerical simulation show that random waveguides and multi-path effects can bring much additional transmission loss for the noise line spectra, demonstrating the instability of ship radiated noise line spectra to a certain extent, and providing some theoretical support for advanced studies of ship radiated noise.
文摘A sound pulse scattering from an edge of thick plates is experimentally and numerically investigated. Beside the edge diffracted signal, waves radiated by the plate that are excited from the plate edge are also detected in the diffraction process. The phenomena are examined by the elastic plate theory and agrecment is observed. The finite difference method (FDM) is used in the numerical calculation. Field distribution around the plate edge and fields at certain points as functions of time are displayed. Comparison is made with experiments. It is found that the grid size of FDM formulation may affect accuracy of computation significantly, but the results show the same phenomena as that measured in experiments.
文摘This paper presents a method to control the gain within pulse and accurately measure the amplitude of an underwater sound pulse in a wide dynamic range. In the method a loop composed of a gain controlled unit and a microcomputer is employed.This method also gives satisfactory results when there exist distortion of signal cnvelop and fluctuation of signal amplitude. The basic mathematical model of instantaneous amplitude-gain control and amplitude measurement and its hardware structure are presented. The calibration method of the system for retransmitting (responding) with required sound level is given as well.
基金Supported by the Post-Doctorate Science Foundation.
文摘Detachment size determination with an acoustic method has been carried out for two interacting bubble plumes formed at neighboring needles in quiescent water. Two sets of needle pairs, one with 1.5mm and 0.8mm inner diameters and the other with the equal 1.5mm inner diameters, were separately used as the bubble pair injectors in the experiments. Consequently, four typical patterns of bubble plumes interaction could be observed in the two cases of needle pair matches. Through measuring the pressure pulses radiated by the bubble pairs immediately after their 'pinching-off ' and by making use of a sophisticated relation between oscillation frequency of volume mode and radius of gas bubble, the detachment size of the bubble plumes have been determined from the amplitude/frequency spectrum of the sound pressure pulses. The experimental results demonstrate that the acoustical method is valid in both of the interacting and non-interacting circumstances in bubble field and the bubble size measurements by this acoustical method agree well with the measurements from photographic analysis. Finally, a comparison has been made on the strong and weak points of the acoustical method with the other size determination methods.
