METHOD AND APPARATUS FOR ADAPTIVE WALL FILTERING PROCESS IN SPECTRUM DOPPLER ULTRASONIC IMAGING

PROBLEM TO BE SOLVED: To provide a method and apparatus for performing an adaptive wall (high-pass type) filtering process for eliminating a low-frequency clutter in spectrum Doppler I/Q data before FFT process. SOLUTION: The I/ Q data is passed through a low-pass filter. The total power of the outputs of the low-pass filter is calculated. Using a system noise model, average system noise power in the output of the low-pass filter is anticipated. The noise power provides a noise threshold which serves as the measure of clutter power existing in a current FFT packet. When there is no significant clutter, wall filter selecting logic selects a minimum wall filter cutoff frequency stored in a filter coefficient lookup table (LUT). When there is significant clutter power, the average and dispersion of clutter frequencies over the FFT packet are estimated and inputted to the filter selection logic to select a filter cutoff frequency which is best suited for the current clutter signal.