A Dual-Band Wideband Antenna on Thin Polyimide Film with Rectangular Slot-Loaded DGS

This paper presents a dual-band, wideband, high-efficiency flexible circular patch antenna for n77, n78, n79, and X band applications. The proposed antenna consists of a circular radiation patch fed by a coplanar waveguide (CPW) using conductive silver ink mounted on the top surface of the low-profile $50 \mu \mathrm{~m}$ polyimide film. At the substrate’s bottom side, a rectangular slot-loaded defective ground structure (DGS) is added to facilitate $50 \Omega$ impedance matching and enhance the antenna impedance bandwidth. This low-profile antenna design works at two different frequencies, exciting $\mathrm{T M}_{11}$ and higher-order $\mathrm{T M}_{21}$ modes. One operates at 4.4 GHz with a fractional bandwidth (FBW) of 39.9%, while the other operates at 10 GHz with an FBW of 31.1%. At 4.4 GHz and 10 GHz resonating frequencies, the individual efficiencies are 88% and 91.3%, respectively. This thin film dual-band antenna offers a wide FBW exceeding 20% and a high efficiency of $\gt80 \%$ across both passbands.