There are provided embodiments for changing initial values of a mid-point algorithm to calculate a constant delay value throughout depths based on a sample volume and performing a receive-focusing based on the constant delay value. In one embodiment, an ultrasound system comprises: an ultrasound data acquisition unit configured to calculate a constant delay value throughout depths based on a sample volume by using a mid-point algorithm, transmit ultrasound signals to a living body, receive ultrasound echo signals from the living body and form digital signals based on the ultrasound echo signals, the ultrasound data acquisition unit being further configured to apply the constant delay value to the digital signals to acquire ultrasound data corresponding to a high pulse rate frequency Doppler image of the sample volume.
