Obstructive sleep apnea (OSA) is receiving increasingly more attention as it is not only related to the quality of daily life but also to various cardiovascular diseases [1]. Since self-awareness of OSA is difficult and calls for expensive in-hospital examination, a portable inhome sleep apnea monitoring system has been proposed [2]. To meet the requirement of a level-4 sleep test, the sleep monitoring system must acquire at least 3 basic parameters: airflow at the nostril, oxygen saturation (SpO2) and heart rate (HR) at the fingertip. The system must also have a small form factor for user's comfort and consume low-power to minimize battery size.