Experimental Investigation of Bending Impact on Radiation Characteristics of Coating-based Flexible Multiband Antenna

This paper presents the experimental investigation of bending impact on the radiation characteristics of flexible multiband antenna inspired by the Halal logo shape widely used in Indonesia. The substrate of antenna utilizes polyethylene terephthalate (PET) material to achieve its flexibility, and the Halal logo-shaped radiating element is realized using a copper conductive coating. The investigation is conducted experimentally under three different scenarios: firstly, in flat configuration; secondly, in bent configuration with the curvature radius (R) of 100 mm; and lastly, in bent configuration with <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$R$</tex> of 50 mm. These three scenarios are performed for reflection coefficient (S11) to evaluate the influence on its operating frequencies. Furthermore, the characteristics and variations in radiation patterns and gains are also assessed for each scenario. From the experimental measurements, the developed coating-based flexible antenna produces multiband frequency responses with the minimum S<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</inf> positions occur at the frequencies of 0.82 GHz, 1.68 GHz, 2.40 GHz, 3.68 GHz, 4.74 GHz, and 5.68 GHz. When the antenna is in bent configuration with <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$R$</tex> of 100 mm, the minimum S<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</inf> positions are at the frequencies of 0.78 GHz, 1.66 GHz, 2.34 GHz, 3.64 GHz, 4.62 GHz, and 5.54 GHz. While, in case the curvature radius is reduced to 50 mm, the minimum S<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</inf> positions occur at the frequencies of 0.78 GHz, 1.64 GHz, 2.32 GHz, 3.52 GHz, 4.56 GHz, and 5.60 GHz. In the assessments of radiation patterns and gains, the developed antenna maintains its radiation characteristics effectively in both flat and bent configurations.