Ultrasound second harmonic imaging with a weighted chirp signal

In this paper, a new harmonic imaging technique is proposed and evaluated experimentally. In the proposed method, a weighted chirp signal with a Hanning window is transmitted. The RF samples obtained on each array element are individually compressed by correlating with the reference signal defined as the 2nd harmonic component ( 2f₀) of a transmitted chirp signal generated in a square-law system. The proposed method uses the compressed 2f₀ component to form an image, for which the crosscorrelation term should be suppressed below at least -50 dB. Another advantage of the proposed method is that the SNR of 2nd harmonic imaging can be improved without limitation by increasing the duration of the chirp signal