In this thesis signal-to-noise ratio improvement method in the ultrasonic synthetic focusing are studied. Compared to the conventional dynamic focusing the signal-to-noise ratio of an image in synthetic focusing is worse, because in synthetic focusing one or two elements transmit the pulse.
Generally, matched filter method gets the highest signal-to-noise ratio. The proposed method is matched filter method is matched filter method with linear FM signal. Transducer element transmit linear FM signal and matched filter coefficients are reverse of received signals.
The computer simulation shows that the proposed method improve signal-to-noise ratio. But, when experiments in a water tank were performed, some unexpected problems occurred. These problems result from non-linearity and distorsion of transducer, power amp, pre-amp, and other systems. These problems occur worse axial resolution. With concerning these system problems, the best waveform is determined for best output signal. By this generated waveform, all experiments are reperformed. And all result images show high signal-to-noise ratio and high resolution.
