Research and experimental verification of broadband beam pattern design method for compact transmitting transducer array

The broadband compact transmitting array has more complex amplitude and phase characteristics as well as array element consistency compared to the narrowband transducer array, resulting in limited broadband transmitting performance. To solve this problem, the space-frequency response matrix is proposed to design broadband beam patterns of the compact transmitting array. First, since the broadband signal can be decomposed into the superposition of narrowband signals, the broadband space-frequency response matrix can be derived after expanding the spatial response of the compact transmitting array accordingly. Then, the radiated acoustic field of the transducer array can be equivalent to a generalized channel, therefore, orthogonal frequency division multiplexing signals are used to quickly measure the space-frequency response matrix of the compact transmitting array in an anechoic water tank. Finally, the constant beamwidth beamforming method that can suppress side lobes has been developed according to the measured space-frequency response matrix, and the designed broadband transmitting beam patterns are also measured in an anechoic water tank. The experimental results show that the proposed method can significantly reduce side lobe levels and improve the broadband transmitting directivity of the compact transducer array.