ABSTRACT
(Ultrasound) This is a high-pass filter that blocks low-frequency components of the Doppler signal. In Doppler measurements, the Doppler shift frequency is detected. If however the target is stationary, a DC-signal is received. This corresponds to the phase shift between the transmitted and received signals, which is constant as the target is stationary. As tissue has on the order of 10–100 times higher scattering strength than blood, a high-pass filter must be inserted in order to eliminate this DC-component. Otherwise, the lower part of the power spectrum may be distorted due to windowing and segmentation of the data. High DC-components can also be a problem in the signal processing due to clipping and thereby distorted results.
