Tolerance analysis and apodization processing of medical ultrasonic array transducer wave beams

The directivity function is used for determining the beamforming wave properties of ultrasound array for medical use. It is affected by efficiency loss of elements, amplitude and phase error distribution of array elements. A method is developed by combining amplitude weighting, phase and aperture apodization for improving beam patterns. The computed results show that (1) Phase error and Gauss distribution amplitude error give rise to larger sidelobes, more grating lobes and deteriorating beam quality whose effect to sound field properties was determined by error distribution. (2) Amplitude weighting and phase apodization processing can restrain sidelobes and improve the directivity effectively. (3) In an ultrasound array system with fixed transmitting aperture and changeable receiving aperture, there exists a best receiving aperture, at which sidelobes are the lowest. This conclusion is important for the medical and industrial application of ultrasonic.