Low-Power Radar System for Noncontact Human Respiration Sensor

The development of a radar system for human respiration noncontact sensor will contribute to the healthcare field, particularly in the monitoring of patients’ respiration for a long period with all the while providing more advantages, such as hygiene and comfort. The radar system must be able to detect the small displacement with millimeters or centimeters scale on the human body associated with the respiratory activity. The minimum power of electromagnetic wave radiation is also needed to avoid unsafe usability in patients’ respiration monitoring. To attain low power operation and efficient frequency spectrum usage, the multifrequency continuous-wave (MFCW) radar system is proposed in this article as a noncontact sensor for human respiration. The simulation study and laboratory experiment of the MFCW radar system in detecting human respiration were performed, and the comparison study with frequency-modulated continuous-wave (FMCW) radar was discussed in this article. The simulation shows that the effective isotropic radiation power (EIRP) of MFCW is 9 dBm lower than FMCW at a 2-m measurement distance. The result also demonstrates that the proposed MFCW performs well under amplitude and phase noise. The laboratory experiments were conducted by implementing the proposed system using the software-defined radio device. The experiment results also confirm that the proposed MFCW was able to reduce the EIRP and spectrum occupation compared to the FMCW. The MFCW system is then recommended as a radar system in developing a noncontact sensor for respiration monitoring in healthcare.