DESIGN OF WEIGHTS BASED ON THE VIRTUAL ARRAY TRANSFORMATION OF UNIFORM CIRCULAR ARRAY FOR ULTRASOUND IMAGING

In applications such as endoscopic ultrasound imaging, uniform circular arrays (UCAs) are attractive since they are naturally suited to offer 360 degrees of coverage in azimuth. The design of aperture weights for beamforming is a crucial step in the development of ultrasound imaging system. However, the conventional weighting functions, known for their interference rejection capabilities, are mostly suitable for uniform linear arrays. They are not optimal for UCAs. In this paper, a virtual array transformation technique is proposed to design the weights for the beamformer of UCAs. The main idea is transforming UCAs into virtual nonuniform linear arrays. By using the positions of the virtual linear array elements, suitable weights of the UCA are obtained from conventional weighting functions. And the process has very low complexity. The simulation results demonstrate that the designed weights have a better performance than the conventional weighting functions on the aspects of the sidelobe control of beampattern and the contrast of image.