| 摘要 |
With a natural number n, an ultrasound pulse having a center frequency of nf0 is transmitted, and an echo wave produced by the reflection at an acoustic-impedance interface within the object to be examined is received. Another ultrasound pulse having a center frequency of (n+1) f0 is transmitted, and, similarly, an echo wave produced by the reflection at an acoustic-impedance interface within the object to be examined is received. The received echo signal which has a center frequency of nf0 is raised to the power of (n+1) in a self-multiplication unit. Meanwhile, The received echo signal having a center frequency of (n+1) f0 is raised to the power of n in another self-multiplication unit. Each multiplication produces a signal having a center frequency of n (n+1) f0. A signed echo signal is obtained by a phase-sensitive detection between the two obtained signals.
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