ULTRASOUND HARMONIC GOLAY-CODED EXCITATION WITH DIFFERENTIAL PULSING

摘要

Harmonic imaging using harmonic Golay-coded excitation that encodes the fundamental (64) and second harmonic signals (66) utilizes the transmit sequences encoded using QPSK implemented as quarter-cycle circular rotations or shifts of the base pulse. This is implemented by time shifting the chips of the transmit sequence encoded with a "j" or "-j" code symbol by 1/4 fractional cycle at center frequency relative to the chips encoded with a "1" or "-1" code symbol. A different QPSK transmit code is used for each of four transmits A, B, C and D. The transmit codes are selected such that (A-B) and (C-D) are encoded by Y and -X, respectively, while (A2-B2) and (C2-D2) are encoded by X and Y, respectively, where X and Y form a Golay code pair. The coding and decoding technique achieves fundamental suppression and second harmonic compression for a given Golay code pair X and Y.