This paper describes in detail an acoustical array structure with four elements that have cosine directivity function over a certain frequency range. The acoustical axis directions of these elements are orthogonal to ...This paper describes in detail an acoustical array structure with four elements that have cosine directivity function over a certain frequency range. The acoustical axis directions of these elements are orthogonal to each other, so their beams cover all bearing angles within 360° . By use of the amplitude bearing method, it is easy to detect the bearing of incident acoustic signal. A special sound reflection foam rubber is designed as a back baffle of the array. It has been shown, in practice, that the constant beam-width has been obtained for a multiple frequency band of the ratio of 8:1. The paper also gives a mathematical model for the array structure. The theoretical values are consistent with the measured results.展开更多
A novel wideband beam-forming structure with constant beam width based on complex coefficients (FIR) digital filters used in underwater acoustic communication is proposed. First,the received signals are compensated wi...A novel wideband beam-forming structure with constant beam width based on complex coefficients (FIR) digital filters used in underwater acoustic communication is proposed. First,the received signals are compensated with integer sampling period by using delay line. Then their complex envelopes are calculated by using frequency shift method. Finally,the envelopes are weighted by using complex coefficients FIR digital filters whose coefficients are optimized. Simulation results show that,in the communication band,the maximum difference between the designed beam and desired beam is less than 0.3 dB when the ratio of communication band to carrier frequency is 0.85.展开更多
文摘This paper describes in detail an acoustical array structure with four elements that have cosine directivity function over a certain frequency range. The acoustical axis directions of these elements are orthogonal to each other, so their beams cover all bearing angles within 360° . By use of the amplitude bearing method, it is easy to detect the bearing of incident acoustic signal. A special sound reflection foam rubber is designed as a back baffle of the array. It has been shown, in practice, that the constant beam-width has been obtained for a multiple frequency band of the ratio of 8:1. The paper also gives a mathematical model for the array structure. The theoretical values are consistent with the measured results.
基金Sponsored by the project supported by the National Natural Science Foundation of China(60672046)the Natural Science Foundation of Fujian Province of China(2010J05139)
文摘A novel wideband beam-forming structure with constant beam width based on complex coefficients (FIR) digital filters used in underwater acoustic communication is proposed. First,the received signals are compensated with integer sampling period by using delay line. Then their complex envelopes are calculated by using frequency shift method. Finally,the envelopes are weighted by using complex coefficients FIR digital filters whose coefficients are optimized. Simulation results show that,in the communication band,the maximum difference between the designed beam and desired beam is less than 0.3 dB when the ratio of communication band to carrier frequency is 0.85.
