Miniaturized Circularly Polarized Doppler Radar for Human Vital Sign Detection

• Published in: IEEE transactions on antennas and propagation Vol. 67; no. 11; pp. 7022 - 7030
• Main Authors: He, Yuchu, Gu, Changzhan, Ma, Haijiang, Zhu, Jiang, Eleftheriades, George V.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.11.2019; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Antenna arrays; Apertures; Circular polarization; Continuous radiation; Couplers; Doppler radar; Gain; Linear polarization; patch antenna; Patch antennas; Polarization; Quadratures; Radar antennas; Radar equipment; Radar systems; Size reduction
• ISSN: 0018-926X; 1558-2221
• DOI: 10.1109/TAP.2019.2927777

In this paper, a miniaturized circularly polarized (CP) continuous wave Doppler radar system operating at 2.4 GHz is presented. The radar front end consists of one left-handed CP (LHCP) antenna and one right-handed CP (RHCP) antenna, which share a single patch antenna aperture. Orthogonal polarization is achieved through a modified ring-shaped quadrature hybrid coupler (QHC), and the resulting isolation between the two CP antennas is better than 30 dB. With 0 dBm input power to the transmitting antenna, the proposed radar system can accurately detect heartbeat and respiration movements of human test subjects under 1 m and over a wide angular range. The single dual CP antenna achieves 280% size reduction compared to a traditional two linear polarization patch antenna array with the same isolation level.