Abstract: A data interpolation processing apparatus used in an ultrasonic diagnostic system and having an interpolation arithmetic unit for obtaining indication data related to a point of interest using a total of eight sampling data. The eight sampling data are located on a total of four scanning lines which include two scanning lines placed on each of opposite sides of the point of interest in the scanning direction, and which include two sampling data on each of the four scanning lines, wherein each of the two sampling data are placed on the opposite sides of a line extending in the scanning direction and passing through the point of interest.

Abstract: A frequency of a signal, particularly a frequency, partly varied as time passes, of a signal is counted in real time by producing a delay signal by delaying the signal as much as a predetermined time, detecting delayed zero-cross pulses from the delayed signal, detecting zero-cross pulses from the non-delayed signal, counting a first number of the delayed zero-cross pulses after the predetermined time is over, counting a second number of the zero-cross pulses during and after the predetermined time, producing a number difference between the first number and the second number by subtracting the first number from the second number and halving the number difference. The predetermined time is designated longer than a half period of the signal frequency to be counted. When the predetermined time is set long, the average frequency of the signal is counted, and when that is set short comparing with the partly varied interval of the signal frequency, the partly varied frequency of the signal is counted in real time.