| 摘要 |
PURPOSE:To attempt to improve sensitivity by correcting a level of a beat frequency signal from a mixing device in accordance with the distance of a subject after the signal is attenuated in a low region, lowering it rapidly at a specified level point to obtain a distance distribution data and elevating the rate of application of a wave transmitting energy. CONSTITUTION:An ultrasonic receiving signal of an examined body is multiplied with a continuous wave from a local oscillator 1 in a mixer 5 through a probe 3 and an amplifier 4 and is detected and a reflection signal corresponding to the distance of the subject and the deviation of the frequency is output. Then, a high level reflective wave based on the examinee body in a short distance echo cut region 11 is attenuated by the characteristics of an equalizer filter to reach a specified level and a weak ultrasonic receiving signal of a faraway subject is elevated based on the characteristics of a slope and when it reaches a specified level, it suddenly decreases caused by a cutoff characteristics and a distance distribution data is calculated. Then, a frequency analysis is performed by means of FFT 8 through an A/D convertor 7 and an image of the subject is displayed on a display 9. It is thereby possible to increase utilization of a wave transmitting energy and to attempt to improve sensitivity. |
