Model-Based Estimation of Heart Movements using Microwave Doppler Radar Sensor

This paper describes the development of a non-contact method for continuously estimating heart movements using a microwave Doppler radar sensor. With this method, mathematical models of cardiac physiology, i.e. the shape and movements of the heart, are created, and Doppler reflected waves are simulated based on these models. In this study, eight subjects were measured and analyzed for one minute, seated shallowly in a chair in the rested state with breathing and body movements allowed. Sinusoidal and extended triangular wave models based on cardiac physiology were employed as the mathematical models. Evaluations of cross-correlation coefficients obtained with the two models showed that those of the extended triangular wave model exceeded 0.9 while those of the sinusoidal wave model were around 0.7. The findings also revealed that extended triangular wave model parameters that maximize cross-correlation coefficients, such as heart radius and extended triangular wave, differed by subject. For instance, the estimated heart radii ranged between 4.2 cm and 7.0 cm depending on the subject, which is consistent with the findings of medical studies that report the heart radii of men and women in Japan to be about 5 cm. These results confirm the validity and effectiveness of the proposed method.