| Microwave Doppler radar can be used for non-contact, through-clothing measurement of chest wall motion, from which heart and respiration signatures and rates can be derived in real-time. A heart and respiration rate monitor has been developed based on this principle and the radio electronics have been integrated on a single CMOS chip, making inexpensive mass-production and miniaturization of the system possible.; This dissertation thoroughly explores the design requirements and trade-offs for this system, analyzing the transceiver architecture, circuit specifications, and the effects of phase noise on the system. In a direct-conversion receiver, the phase relationship between the received signal and the local oscillator has a significant effect on the demodulation sensitivity, and the null points can be avoided with a quadrature receiver. The range-correlation effect on residual phase noise is a critical factor when detecting small phase fluctuations with a high-phase-noise on-chip oscillator. Phase noise reduction due to range correlation has been experimentally evaluated, and the measured phase noise was within 5 dB of predicted values on average.; Data is presented from the method comparison study in which heart and respiration rates measured with the 0.25-mum CMOS quadrature Doppler radar system were compared with those measured with standard techniques on 22 human subjects. The data from the method comparison study is used to confirm theoretical estimates of the SNR, to evaluate techniques for combining the quadrature output signals and to evaluate techniques for determining the heart rate from the heart signature.; The current version of the single-chip Doppler radar cardio-respiratory rate detection system can successfully measure heart rate up to one meter and respiration rates up to two meters in most subjects that have been instructed to sit still, and it could be used to monitor sleeping or unconscious persons from a relatively close range, avoiding the need to apply electrodes or other sensors in the correct position and to wire the subject to the monitor. A CMOS single-chip version of this technology offers a potentially inexpensive implementation that could extend applications to consumer home-monitoring products, and could enable the use of multiple transceivers to solve some system-level problems. |
