A Wideband Flexible Antenna on 100µm Polyimide Film with Mild Curvature Deformation-Insensitive

A compact flexible 3.5 GHz antenna built on a 100 µm flexible polyimide film, tested in the presence of mild curvature deformation, is presented. The proposed antenna, with a total dimension of 0.45 × 0.35 × 0.0013 λ³, is comprised of a circular radiation patch fed by a coplanar waveguide (CPW) coated with a layer of conductive silver (Ag). A rectangular slot-loaded defective ground structure (DGS) is included at the bottom of the polyimide film to help in achieving 50 Ω impedance matching. When subjected to a curvature deformation case with an arch length (lc) of 25 mm, the proposed flexible antenna maintains a stable resonant frequency at 3.5 GHz, with an efficiency exceeding 90%, while operating across a wide frequencies range. This flexible antenna is well-suited for use in wearable smart device applications due to its established invariant operating frequency, even when exposed to arbitrarily slight deformation.