Non-contact heart rate monitoring method for elderly people In bed with random body motions using 24 GHz dual radars located beneath the mattress in clinical settings.

We have developed a non-contact heart rate monitoring system for elderly people In bed using two radars placed on the bed base. The system is designed to increase accuracy despite body motion noise and change of body position and sleeping posture In bed. In order to achieve this, we combined an automatic gaIn control (AGC) method with a real-time radar-output channel selection method which is based on a spectrum shape analysis (SSA). Field tests were carried out with elderly subjects at a nursing home. The accuracy was maintained because the system successfully avoided the null detection point (NDP) problem, respiratory harmonic interference and intermodulation problems. The heart rate accuracy (r = 0.703) was higher than that of the conventional method. The system was proved to be effective In monitoring vital signs without the need for any physical contact with the subjects.