In this work, we proposed and verified that a noncontact measurement to the human cardiogram could be implemented based on the inner connection between the bioelectrical signals that control the diastole and systole of human hearts and the volume change of atriums and ventricles taking place at the surface of skin. A K-band, board-integrated, highly linear and sensitive Doppler radar sensor was designed and implemented to detected such weak motions. Experimental results showed that by linearly retrieving the Doppler information from the signals scattered by the skin, the cardiogram can be measured. While the correspondence between this kind of cardiogram and the conventional ECG can be observed. And the cardiogram also includes velocity and strength information of the atrial and ventricular contractions and relaxations. Such characteristics are highly desirable for hospitalization and personal daily healthcare.