Ultra Wide Band (UWB) radars are effective in detecting subtle fluctuations of illuminated target. This attribute makes them attractive for uncovering respiration and circulation patterns from chest movements. Despite the acute range resolution offered by Doppler radars, contribution by cardiovascular pumping is quite feeble and is overshadowed by breathing. It is observed that, when chest movements were monitored using UWB pulse Doppler radars, cardiac motion is buried at least 30 dB under first harmonic of respiration. In this paper, we propose and investigate novel Arctangent demodulation method for direct-RF receivers. The proposed method offers an improvement of signal-to-noise ratio by 8-15 dB of cardiopulmonary motion signal when compared to existing algorithms. In addition, it enables adaptive suppression of respiratory artifacts using trend filtering which vastly enhances robustness in real-time non-invasive heart rate monitoring applications.