PROBLEM TO BE SOLVED: To provide tissue generating higher harmonic-enhanced imaging using encoding excitation for a medical ultrasonic imaging system. SOLUTION: Two-phase (1 and -1) encoding is performed on a transmitted waveform by using two code symbols in a code sequence for obtaining an N- nary higher harmonic signal. Each part (namely, each chip) of the transmitted waveform encoded by means of the second code symbol is shifted in phase by 180 deg./N against the chip encoded by means of the first code symbol. This processing is accomplished by shifting in time each part (each chip) of a transmitted sequence encoded by means of the second code symbol by the 1/2N period at the center frequency against each chip of the transmitted sequence. At the time of reception, emphasis is performed by decoding by separating a desired higher harmonic signal by means of a band-pass filter having a center frequency which is twice as high as that of a fundamental wave.
TISSUE GENERATING HIGHER HARMONIC-ENHANCED IMAGING USING ENCODING EXCITATION