VLSI implementation of real-time motion compensated beamforming in synthetic transmit aperture imaging

Synthetic transmit aperture (STA) has been widely investigated in ultrasound system recently due to its high frame rate and low cost characteristics. Since the high-resolution image (HRI) of STA is formed by summation of low-resolution images (LRIs), it is susceptible to motion between firings. In this work, we propose a low-complexity two-dimensional motion compensation algorithm. The velocity and direction of motion can be evaluated by cross-correlation between specific beams according to geometry characteristics of STA. Compared to the uncompensated image, simulation results which used Field II program show that proposed method can improve the contrast ratio (CR) and contrast noise ratio (CNR) about 8.6 dB and 1.3 dB. The whole imaging system was implemented in TSMC 90nm technology. Operating at 125 MHz, the circuit with 11% hardware overhead for motion compensation can beamform 64 image lines consisting of 1024 complex samples at the rate of 45 frames per second.