A noncontact measurement of the heart rate of a specific person using an X-band radar system with a four-element antenna array is presented. The system comprises a two-dimensional planar wide-beam antenna array with a four-channel network analyzer. The direction of arrival is estimated using the Capon method, and the directionally constrained minimization-of-power algorithm is then applied to the received signals. Signals from the four channels are adaptively combined to enhance the accuracy in estimating the instantaneous heart rate in a multi-person scenario. Measurement results indicate that the proposed system with the adaptive array processing technique is effective for the noncontact measurement of the heart rate of a specific person when there are more than one person in the scene.@en