Designing an optimal digital bandpass filter for 3D USCT II

3D-USCT-II is a novel imaging method aimed at detecting breast cancer at an early stage by using Synthetic Aperture Focusing Technique (SAFT). The excitation signal (Coded Excitation), used as an input signal, goes to the receiver transducer, and is then fed into a signal processing chain where a digital filter is used with a bandwidth from 1.66 MHz to 3.33 MHz, which is also defined as its digital bandwidth. The analog bandwidth of the signal, however, begins below 1.66 MHz. Therefore, there is considerable loss of bandwidth with the usage of this digital filter. A solution presented here makes use of modulation to assist the bandwidth increase of the digital filter. Results are then compared with metrics defined by SNR, increase in bandwidth, and increase in signal fidelity. The results show an increase in bandwidth by 15.06%, increase in SNR by 7.72% and increase in signal fidelity by 5.76%.