Abstract
Noncontact monitoring of human vital signs has been 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. 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 radiation directivity and mechanical flexibility. This paper presents the design of a four-element antenna array on a flexible liquid crystal polymer (LCP) substrate of 100 μm thickness and εr of 3.35. The designed antenna array can be used with a 24 GHz bio-radar for vital signs monitoring in a non-contact manner. It features a relatively compact size of 36.5 × 53 mm2 and measured gain of 5.81 dBi. 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 array and radio frequency (RF) output power of −3 dBm from a distance of approximately 60 cm. The effect of bending on the antenna performance is also analyzed.
Highlights
To the best of our knowledge, the flexibility feature has not been explored by bio-radar systems that operate in the far-field for vital sign monitoring
Patch antenna dimensions were calculated, and simulations were conducted to optiHence, three flexible patch antennas were designed to operate at 24 GHz: (i mize the design in terms of size and performance, resulting in an ellipse-shaped slotted element array;were andthen (iii)designed four-element array
This paper firstly presented the design of a single-element unit cell that features an elliptical and horn-shaped patch on flexible liquid crystal polymer (LCP) substrate for a 24 GHz bio-radar
Summary
The above reasons motivated recent investigations into contactless-based sensing, and radar-based sensing at microwave frequencies [1] appears to be a promising alternative to conventional implantable or wearable sensors for vital signs monitoring This leads to the concept of bio-radar [2], which promises to revolutionize the healthcare industry. The antennas are a key component of any bio-radar module as transmission and reception of the signal with minimum losses is the key to a successful operation They can be composed of a single element or an array of multiple elements, can be designed for different frequencies, and use different types of substrates.
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