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Date:  Tue, October 25, 2016
Time:  2:30pm - 4:30pm
Location:  Holmes Hall 389
Speaker:  Shuhei Yamada, candidate for PhD, advisor: Victor Lubecke

Microwave Doppler radar systems can be used to measure human vital signs by tracking torso displacement. Technical requirements for such systems depend on the intended subject, purpose, resolution and sensitivity, and on practical constraints such as cost, size, and power consumption. Due to its simple structure and validity, direct conversion systems are commonly used for vital signs detection applications. One problem with such systems is that motion/displacement measurement accuracy is often compromised by the presence of dc offset which limits the overall signal to noise ratio (SNR) and the system resolution. While the portion of dc offset caused by system imperfections, internal dc offset, and the external environment, clutter, is problematic, the dc offset contributed from the subject is critical for accurate displacement measurement. In this research, dc offset optimization methods for direct conversion systems is studied. With this proposed method, it is possible to make measurements of time varying signals which preserve useful dc contributions while eliminating non-essential dc contributions which would otherwise undermine the use of appropriate gain and resolution. The performance is contrasted with ac coupling method using high-pass or band-pass filters and other established dc management approaches.