Wearable Doppler radar with integrated antenna for patient vital sign monitoring

A 2.45 GHz wearable Doppler radar unit with radio data link is presented for use in portable patient monitoring and emergency response. Unlike portable Electrocardiograms (ECG) or Photoplethysmography (PPG), the near-field Doppler unit enables monitoring of the person´s heart rate without the need for electrical contact or optical access to the patient´s skin. The Doppler unit is designed to be embedded in a clothing garment such as a shirt or vest, or used by medical emergency personal in an instrumented blanket or medical stretcher. Since the Doppler unit is placed directly on or behind the patient´s torso, the extraneous signals due to relative motion artifacts is greatly reduced. Low-cost design is achieved by employing PWB microstrip elements for the integrated patch antenna, microwave oscillator, and tuning elements. Also, since the distance between the Doppler unit and the patient is fixed, it was possible to tune the detection phase to enable the use of a single mixer diode and eliminate the need for quadrature detection. Measured heart data from this technique shows clear waveform substructure similar to PQRST complex features found in captured ECG data.