Ultracompact Dual-Band Implantable Antenna for Capsule Endoscopy Systems

In this letter, a highly compact dual-band implantable antenna is developed for capsule endoscopy with an overall size of${\text{4}}\, {\text{mm}}\times {\text{4}}\, {\text{mm}}\times {\text{0.13}}\,{\text{mm}}$(${\text{2.08}}\,{\text{mm}}^{{\text{3}}}$), making it well suited for integration inside the small intestine. Miniaturization is achieved by combining a high-permittivity Rogers RO3010 substrate with a slot-loaded radiator and an optimized ground plane, which effectively extends the electrical current path without increasing the physical dimensions. The antenna operates at$\mathbf {{1.41}\,{GHz}}$(WMTS) and$\mathbf {{2.45}\,{GHz}}$(ISM), providing −10 dB impedance bandwidths of$\mathbf {{1.37}}$GHz to$\mathbf {{1.51}\,{GHz}}$($\mathbf {9.36\%}$) and${\text{2.32}}$GHz to$\text{2.52}$GHz (${\text{7.8}}\%$), respectively. In a tissue-equivalent small-intestine environment, it maintains stable radiation characteristics with peak realized gains of approximately$-{\text{23}}\,{\text{dBi}}$at${\text{1.41}}\,{\text{GHz}}$and${\text{-14.8}}\,{\text{dBi}}$at${\text{2.45}}\,{\text{GHz}}$. Safety is verified through 1 g SAR analysis, yielding 496 W/kg and 677 W/kg at the two operating bands, which correspond to maximum permissible input powers of 3.22 mW and 2.36 mW, respectively, under Federal Communications Commission (FCC) exposure limits. These results demonstrate that the proposed antenna effectively combines extreme miniaturization, reliable dual-band operation, and safe in-body performance, making it a strong candidate for next-generation wireless capsule endoscopy systems.