A Portable Doppler Device Based on a DSP with High- Performance Spectral Estimation and Output

A low-cost and high-performance portable Doppler blood flow analysis device, which is based on a digital signal processor (DSP) TMS320V549 (Texas Instruments), contains a 240 * 320 LCD color graphic display module (Hantronix) and a thermal printer (Seiko Instruments), is developed in this study. The complex real-time autoregressive (AR) modeling is implemented in this device to estimate the time frequency representation of blood flow signals. Directional Doppler spectrograms are computed directly from the in-phase and quardrature components of the Doppler signal. Sampling frequency can vary among 5kHz, 10kHz, 15kHz, 20kHz and 25kHz to optimize the displaying dynamic range according to the blood velocity. In order to increase the display quality and provide more comprehensive information about the components of the blood flow profile, The Doppler spectrograms can be displayed in real-time on the LCD in 256 colors. They can also be printed out in 13 gray levels from the thermal printer for recording. The Doppler spectrograms computed by the AR modeling are compared with those by the STFT. The results show that this compact, economic, versatile bi-directional and battery- or line- operated Doppler device, which offers the high-performance spectral estimation and output, will be useful at different conditions, including bed-side hospitals and clinical offices.

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