Frequency-shifted array data: Improving beam resolution in underwater acoustic beamforming and enabling separation of pulse sources with the same azimuth

• The definition of the frequency-shifted array data and its physical characteristics in multi-source beamforming. • The extension of frequency-shifted array data to other high beam-resolution beamformers. • The application of frequency-shifted array data to the separation of multiple sources with the same azimuth in shallow and deep water. Affected by beam broadening and splitting, underwater acoustic high-resolution beamforming algorithms may struggle to achieve their theoretical beam resolution capability. Unlike the frequency-fixed (FF) array data used in traditional frequency-domain beamforming, this paper explores the application of frequency-shifted (FS) array data to enhance beam resolution. Frequency-shifted array data is generated through data selection along the element-frequency domain interference striations formed by array signals with different source ranges. This process is equivalent to enhancing the consistency of array signals, thereby avoiding beam broadening and splitting. Such a change at the data level enables the FS array signal processing method to be easily extended to other high-resolution algorithms (e.g., subspace-based algorithms, compressed sensing algorithms) while ensuring their theoretical beam resolution capability. In addition, by leveraging the differences in arrival times of pulse sources with the same azimuth but different positions, beamforming based on FS array data can create differences in beam positions, thereby achieving separation of sources with the same azimuth in the beam domain. The above research content is verified through experimental data and simulation data in shallow-water and deep-water scenarios.