Abstract
The feasibility study of a 24 GHz industrial, scientific, and medical (ISM) band Doppler radar antenna in electromagnetic aspects is numerically performed for near-field sensing of human respiration. The Doppler radar antenna consists of a transmitting (Tx) antenna and a receiving (Rx) antenna close to the human body for a wearable device. The designed slot-type Doppler radar antenna is embedded between an RO4350B superstrate and an FR-4 substrate. To obtain the higher radiation pattern of the antenna towards the human body, a ground plane reflector is placed underneath the substrate. The measured −10 dB reflection coefficient (S11) bandwidth is 23.74 to 25.56 GHz and the mutual coupling (S21) between Tx and Rx antennas is lower than −30 dB at target frequencies. The Doppler radar performance of the proposed Doppler radar antenna is performed numerically by investigating the signal returned from the human body. The Doppler effect due to human respiration is investigated through the I/Q and arctangent demodulation of the returned signal. According to the results, the phase variation of the returned signal is proportional to the displacement of the body surface, which is about 0.8 rad in accordance with 1 mm displacement. The numerical experiments indicate that the proposed Doppler radar antenna can be used for near-field sensing of human respiration in electromagnetic aspects.
Highlights
As we rapidly become a super-aging society, the global medical device market is growing
The wearable device with a strap wrapping the human body can be considered for near-field sensing of human vital signs, because the Doppler radar does not move in relation to the human cardiopulmonary motion or pulse
We study a 24 GHz ISM-band Doppler radar antenna suitable for near-field sensing of human vital signs
Summary
As we rapidly become a super-aging society, the global medical device market is growing. The wearable device with a strap wrapping the human body (e.g., an ID badge holder or a wrist band) can be considered for near-field sensing of human vital signs, because the Doppler radar does not move in relation to the human cardiopulmonary motion or pulse. We study a 24 GHz ISM-band Doppler radar antenna suitable for near-field sensing of human vital signs. This work considers simulations on scenarios with body-RF signals interaction that give a qualitative insight of the feasibility of this antenna system for near-field sensing of human vital signs. We investigate the performance of the designed Doppler radar antenna close to the human body and conduct a feasibility study of the 24 GHz ISM-band Doppler radar antenna for near-field sensing of human respiration.
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