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24 GHz Flexible Antenna for Doppler Radar based Human Vital Signs Monitoring

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Thesis(3.2 MB)

Date

2021

Authors

Supervisor

Seet, Boon-Chong

Item type

Thesis

Degree name

Master of Engineering

Journal Title

Journal ISSN

Volume Title

Publisher

Auckland University of Technology

Abstract

Noncontact monitoring of human vital signs is an emerging research topic in recent years. A key approach to this monitoring is the use of the Doppler radar concept which enables real-time vital signs detection, resulting in a new class of radar system known as bio-radar. Unlike traditional techniques that use contact electrodes for vital sign measurement, bio-radar is non-intrusive and less perturbing for infants and patients with critical injuries. The bio-radar can even detect life under rubble in the aftermath of disasters. The antennas are a key component of any bio-radar module and their designs should meet the common requirements of bio-radar applications such as high directivity, circularly polarized, and flexibility. This thesis presents the design of a 24 GHz four-element antenna array on a low-cost and flexible liquid crystal polymer (LCP) substrate with a thickness of only 100 m, low-loss tangent (tan=0.0021), stable dielectric constant (r=3.35) and low moisture permeability. The designed antenna array can be used with a bio-radar for vital signs monitoring in a non-contact manner. To the best of our knowledge, the design of flexible antenna arrays for bio-radar and the use of LCP for such applications have not been explored in literature. Any antenna array will require a unit element to be designed first. The unit element was designed with an input impedance of 50 Ω on LCP substrate, which is then used to construct a two- and four-element array with an overall dimension of 29.5×25.4 mm, and 5336.5 mm, respectively. The simulated gain obtained is 4.39 dB, 5.46 dB, and 6.68 dB for unit cell, two-element array, and four-element array, respectively. Other measured and simulation results showed close agreement. The two vital signs: breathing rate (BR) and heart rate (HR) of two human subjects are detected with relatively good accuracy using the fabricated antenna arrays and RF output power of -3 dBm from a distance of approximately 60 cm.

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Keywords

Flexible, Antenna, LCP, Vital Sign

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Permanent link

https://hdl.handle.net/10292/13968

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Masters Theses