Doppler-based non-contact vital signs (NCVS) sensor systems can monitor the heart and respiration rates without touching the patient, but the accuracy of the NCVS sensing can be degraded considerably by background clutters and movements artifacts from the monitored subject or other motions in the measurement environment. We have, therefore, developed a high directivity phased-array antenna NCVS system that can significantly increase the sensing accuracy and the monitoring range in a typical office cubicle setting. Depending on the position of the beam spot illuminated on the chest, our custom-made beam-steerable phased array NCVS system at 2.4GHz has demonstrated the accuracy of the heart rate monitoring to be within 2 bpm (beat-per-minute) for 92.5%-99.2% of the time at 0.75m. As the monitoring range is extended to 1-1.5m with beam directly illuminating on the center of the chest, the heart rate monitoring accuracy remains within 5 bpm above 78% of time. With more improvement, this phased array NCVS system should benefit patients considerably for telemedicine and remote monitoring, as the patient's vital signs can be monitored comfortably and continuously in both home and office settings, eventually capable of detecting potential sleep apnea and other respiratory or cardiovascular symptoms in real-time.