| 摘要 |
In performing tissue-generated harmonic imaging using coded excitation, the transmit waveform for acquiring the N-th harmonic signal is biphase (1,-1) encoded using two code symbols of a code sequence, the portions (i.e., chips) of the transmit waveform encoded with the second code symbol each being phase-shifted by 180°/N relative to the chips encoded with the first code symbol. This is implemented by time shifting the portions (i.e., chips) of the transmit sequence which are encoded with the second code symbol by ½N fractional cycle at center frequency relative to the chips of the transmit sequence encoded with the first code symbol. During reception, the desired harmonic signal is isolated by a bandpass filter centered at twice the fundamental frequency and enhanced with decoding.
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