Axial Resolution and Robustness Improvement in Coded Excitation Ultrasound Images Using Fractional Fourier Transform

As the kernels of fractional Fourier Transform (FrFT) are in the form of chirp signals, this transform would be useful for processing and describing linear chirps. In this paper FrFT is used as an alternative for pulse compression of received echo signals in coded excitation ultrasound imaging. Using field II program, axial resolution of match filter and FrFT, as two methods of pulse compression, are compared. Simulation results show that applying FrFT with synthetic transmit aperture lead to about 15dB improvement in discrimination ability of two close reflectors for various depth and central frequency of excitation signals. It is worthwhile noting that, in addition to this improvement, no computational complexity imposed for pulse compression. Using Wigner-Ville distribution, it is shown that the proposed method is more robust than match filter against the frequency dependent attenuation in medium.