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Tablet based real-time Doppler spectrum processing
Norwegian University of Science and Technology, Faculty of Information Technology, Mathematics and Electrical Engineering, Department of Electronics and Telecommunications.
2014 (English)MasteroppgaveStudent thesis
Abstract [en]

By utilizing mobile, low-cost Doppler ultrasound technology in developing countries, the mortality rate of unborn children, small children and pregnant women might be reduced. Two main Doppler techniques which are used in ultrasound are the Doppler spectrum and the Doppler audio. The Doppler spectrum is used for quantitative analysis of the blood-flow while the Doppler audio is used for guidance during recording This thesis presents the implementation of a real-time Doppler spectrum generator and a real-time Doppler stereo audio generator, which is implemented on Android mobile devices; along with real-time ratings and optimizations. The Doppler spectrum implementation was compared to a Matlab implementation, while the Doppler audio was compared to a synthetic test signal. The frequency leakage, in the Doppler stereo audio generation, from positive- to negative Doppler shifts and vice versa was at about −20dB with the synthetic test signal. The performance of a mid- to high-end Android tablet showed high framerates for Fast Fourier-Transform lengths up to 128 with both 75 and 87.5 percent overlap and audio-playback frequencies of 8kHz and 16kHz. The low- to mid-end tablet displayed low framerates with the current implementation. The optimization of the Fast Fourier-transform by utilizing FFTW has shown promising results to increase the framerate on the low- to mid-end tablet. Other ways of improving the framerate on low-end tablets is to turn off the audio or turn off the stereo processing along with reducing the settings on the spectrum generator.

Place, publisher, year, edition, pages
Institutt for elektronikk og telekommunikasjon , 2014. , 106 p.
URN: urn:nbn:no:ntnu:diva-25999Local ID: ntnudaim:11565OAI: diva2:743312
Available from: 2014-09-03 Created: 2014-09-03 Last updated: 2014-09-03Bibliographically approved

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