A non-contact apparatus for monitoring cardiopulmonary activity signals comprises a pulse-series generator configured to generate a series of probing pulses and a series of reference pulses, a transmitting antenna configured to emit the probing pulses to a chest portion and a series of scattered pulses generated from the probing pulses by the scattering of the chest portion, a receiving antenna configured to receive the scattered pulses, a mixer including a first input port configured to receive the reference pulses and a second input port electrically connected to the receiving antenna and a signal-processing module configured to generate cardiopulmonary activity signals after the scattered pulses and the reference pulses are processed by the mixer.