New baseband pulse compression for chirp coded excitation

Abstract

In ultrasound medical imaging, the signal-to-noise ratio (SNR) improvement can be achieved by utilizing the code excitation. To preserve the axial resolution, a pulse compression (PC) is performed by applying a matched filter based on the transmit code. However, the conventional PC method requires a few hundred filter coefficients when compressing elongated code (e.g., chirp) into a short pulse, yielding to considerably high computational complexity. In this paper, an efficient PC method of chirp coded excitation is proposed to lower the complexity burden. In the proposed method, the PC is conducted with the decimated complex baseband data instead of a beamformed radio-frequency (RF) data. Although compression is applied with the complex data, a total computational complexity is reduced by a factor of 4 L2 since L-fold decimation is performed to reduce both data and the number of filter coefficients. The proposed method was evaluated with the phantom study. For quantitative comparison, the -6dB axial resolution for 15 wire targets and the clutter-energy-to-total-energy ratios (CTRs) at a hypo-echoic region were measured. CTR were 27.6 dB and 27.4 dB for the conventional and proposed PC methods, respectively. These results indicate that the proposed method can maintain the performance of pulse compression of chirp coded excitation while substantially reducing computational complexity.