| Summary: | 碩士 === 國立臺灣科技大學 === 電機工程系 === 101 === Compared with conventional single-frequency counterpart, dual-frequency harmonic imaging (DHI) , can effectively use the system bandwidth for enhancement of contrast-to-noise ratio (CNR) by frequency compounding. Though particular Chirp-encoded excitation can achieve high signal-to-noise ratio (SNR) for penetration together with wide signal bandwidth for resolution, it suffers from the central side-lobes because of the mutual interference between two imaging bands. In this study, we take advantage of the phase encoding of complementary Golay pairs to alleviate the mutual interference. Particular Golay combined with the original Golay code to suppress the range side-lobes from second-order interference. To maintain the frame rate another side-lobe suppression technique is also developed using the orthogonality between Golay pairs. Hydrophone experiments show that, the Golay waveform improves the compression quality in DHI as compared to the Chirp counterpart by 13.9% and 11.3%. B-mode phantom imaging show that, the proposed Golay waveform can improves the SNR by 10 dB and effectively eliminates the Side-lobes magnitude (SLM) by 7.5 dB.
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