Adaptive compensation of non-ideal transmitter radiation pattern for synthetic transmit aperture 3D acoustic imaging

In airborne acoustic imaging the synthetic transmit aperture (STA) technology is widely used to improve the lateral resolution limited by the aperture of the microphone array. As for an STA system we use multiple speakers in combination as well as the receiver array, knowing the exact radiation pattern of a speaker is the key factor to properly operate the synthesis system. The ultrasonic signals from a transmitter always have uneven signal strength over the imaging space. Phase changes also occur depending on the distance and direction from a transmitter. As a consequence, a non-ideal radiation pattern of a transmitter used for identifying an imaging space degrades imaging results. We propose an effective measurement method for the transmitter´s non-ideal radiation pattern based on new phase only imaging technology of wall-reflected sound wave. We utilize a deconvoluting Wiener filter for compensating the siderobes of receiver sensitivity pattern.