Comparison of methods for turbulence Doppler frequency shift calculation in Doppler reflectometer

The Doppler reflectometer(DR), a powerful diagnostic for the plasma perpendicular velocity(u⊥) and turbulence measurement, has been widely used in various fusion devices. Many efforts have been put into extracting the Doppler shift from the DR signal. There are several commonly used methods for Doppler shift extraction, such as the phase derivative, the center of gravity, and symmetric fitting(SFIT). However, the strong zero-order reflection component around 0 k Hz may interfere with the calcula...