Fractional Fourier Transform with Pulse Inversion for Second Harmonic Pulse Compression

In ultrasound harmonic imaging with chirp coded excitation, harmonic matched filtering (HMF) is required on the receiving side to perform second harmonic pulse compression to recover signal axial resolution. In the compressed signal, peak sidelobe levels will grow and the mainlobe width may increase under mismatched or overlap harmonic conditions. In this paper, fractional Fourier transform (FrFT) with pulse inversion is proposed for the second harmonic pulse compression. Experimental results are presented which show a, 13.5%, improvement in the mainlobe width, with comparable peak sidelobe levels, when compared with the conventional HMF technique.