High-Performance Flexible Sensing Circular Ring Antenna for Smart Packaging

In this article, a flexible coplanar waveguide (CPW)-fed circular ring antenna is demonstrated as a key component in a smart packaging solution. The CPW-fed circular ring antenna is fabricated on a polyethylene terephthalate (PET) substrate. The proposed sensing antenna is developed for operation in the C-band frequency (~3.9 GHz). The antenna exhibits a frequency shift and changes in return loss (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{11}$ </tex-math></inline-formula>) with bending and deformation. It is observed that the change in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{11}$ </tex-math></inline-formula> is more reliable for quantitative measurements and the change in frequency can be utilized for qualitative analysis. A sensitivity of 8.25 and 7.37 is recorded for lower and higher longitudinal bending conditions in the experimental setup. The sensing antenna demonstrated satisfactory performance with smart chemical packaging to detect and distinguish the bending deformations in the lateral and longitudinal directions. A maximum of ~1.5 cm lateral and longitudinal bending with a resolution of 25 mm is detected using the sensing antenna. The measured sensitivities for packaging experiments are 16.8 and 15.22 for transverse direction and longitudinal direction. The flexible nature of the antenna enables seamless integration into various packaging configurations, ensuring adaptability to diverse environments and applications.