Howtosignalprocessing
The Doppler shift is a change in frequency (and phase) of the reflected signal by a moving object. The Doppler equation usually written in ultrasound textbooks is: Δf = 2 * v * cos(θ) * f0 / c.
- How do you find the maximum Doppler shift?
- What is the minimum Doppler shift?
- What angle provides the maximum Doppler shift?
How do you find the maximum Doppler shift?
The maximum Doppler shift is obtained when θ = 0, whereas in imaging the strongest echoes occur when θ = 90º. The change of frequency is measured and shows how fast the reflector is moving towards or away from the transducer.
What is the minimum Doppler shift?
As implied by the above equation, the impact of the angle on the Doppler shift will be greatest when the angle of incidence is 0 degrees (cos 0 degrees is 1) and least when the angle of incidence is 90 degrees (when the probe is exactly perpendicular to the source, the cos 90 degrees is 0).
What angle provides the maximum Doppler shift?
Thus, Doppler-shift is maximum when the incident angle is near 0° or out of phase at 180°. Then, Doppler-shift has a positive or negative value depending on the flow direction.
