| 摘要 |
PURPOSE:To eliminate a clutter signal of a tissue, etc., for moving at a low speed in a short response time without using a filter whose cut-off characteristic is steep, and also, to optimumly set the cut-off characteristic of the filter from the dispersion of a power spectrum of a clutter, and to improve the measuring accuracy of a blood flow speed. CONSTITUTION:From self-correlation outputs Rcx, Rcy calculated by a self- correlator 17 by outputs x[k], y[k] of an orthogonal detector 5, a clutter frequency computing element 18 calculates a Doppler shift frequency(fc) of a clutter. Subsequently, a clutter eliminating filter 20 eliminates a clutter signal by shifting a zero point of a cut-off band to the Doppler shift frequency(fc) of the clutter. Also, a clutter dispersion computing element 19 calculates a dispersion sigmac<2> of a power spectrum of the clutter from the self-correlation outputs Rcx, Rcy, and the clutter eliminating filter 20 sets optimumly a cut-off characteristic of the filter in accordance with the dispersion sigmac<2> of the power spectrum of the clutter. |
