Noise reduction and spectrum analysis in Doppler blood flow signal processing

In this paper a real-time Doppler module is introduced. In order to reduce the noise and artifacts in the Doppler path, several efforts including emission waveform modification, orthogonal signal generator, range gating of signals, wall filters, section shielding and proper power supply and ground system are implemented. Spectrum estimation methods based on Fast Fourier Transformation (FFT) are carefully investigated with different window type selection, pre and post processing of the data. Finally this Doppler module is embedded into a mother ultrasonic sector scanner, CX-960-II, and high quality Doppler blood flow spectrum images are obtained.