Aging is a serious issue in our global society. Additionally, a smaller working population increases the burden on nurses and other healthcare professionals. To reduce the monitoring burden on nursing, a system that enables quantitative monitoring of the elderly automatically in their home is very desirable. In this paper, we propose a novel system to classify the presence of a person within a designated area using a single microwave Doppler sensor. The proposed system utilizes the respirational signal observed from the sensor and classifies it using a support vector machine. The system was evaluated using 21 subjects and performed as accurately as 99.68%.