Compact doppler radar system for heart rate detection

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2007
Authors
Yamada, Shuhei
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Periodic motion, such as that resulting from cardiopulmonary activity, can be measured with a microwave Doppler radar system. This thesis focuses on the assessment of radio system requirements and critical specifications for such radar sensing systems. The fundamental limitations for transmit power, receive power and range for a functional 2.40Hz IMS band cardiopulmonary radar system were computed and measured, including free space losses, noise, and fundamental heart rate detection limits. The minimum required power for close range rate detection was also assessed. Heart rates for subjects holding their breath or breathing normally were successfully tracked for signal power levels as low as 20 nW. This is the lowest power ever reported for an ISM band CW Doppler radar for heart rate detection. These results can be extrapolated to higher power systems where obstructions and antenna gain similarly impact the signal power available for heart motion detection. A 2.40Hz microwave Doppler radar system was designed for the required assessments, with several transceiver variations fully integrated on printed circuit boards using various antenna configurations. The transceiver boards were 101.6[mm] by 111.6[mm], and included a small on-board oscillator. A multiple antenna system was used to provide more comprehensive data for advanced signal processing, and the modular system could be easily expanded. Issues and means for performance improvement of the system are also reported. Sensitivity was found to be limited by direct conversion architecture and component issues. for which several circuit configurations were explored, achieving significant DC offset and LO leakage reduction. Using DC offset cancelling, flicker noise reduction was also achieved, which significantly affects the SNR at baseband and improved the system sensitivity.
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Thesis (M.S.)--University of Hawaii at Manoa, 2007.
Includes bibliographical references (leaves 59-62).
x, 62 leaves, bound 29 cm
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Theses for the degree of Master of Science (University of Hawaii at Manoa). Electrical Engineering; no. 4993
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