| 摘要 |
PROBLEM TO BE SOLVED: To provide a filtering method and a filter circuit especially for removing low frequency dappler signals from ultrasonic video images relating to an ultrasonic color doppler video system. SOLUTION: A deformed infinite impact response filter 100 to which the principle of an MTI(moving target indicator) system is applied can sufficiently suppress unfit transient phenomena observed from a conventional general IIR (infinite impact response) filter. Also, the characteristic curve of sharp inclination observed from the characteristic curve of the conventional IIR filter can be turned to a small degree. Thus, the frame ratio of the video system is improved and a real time processing is made possible. However, since first three signals outputted from the IIR filter 100 are the signals incapable of precisely indicating the characteristics of the filter, by removing first three data to be the cause of the imprecission in the characteristics of the filter in an output control circuit 200, the deformed IIR filter is realized without losing precision. |
