Hilbert curve inspired miniaturized MIMO antenna for wireless capsule endoscopy

This work outlines the design and development of a miniaturized, conformal, multi-input multi-output (MIMO) antenna on a thin, flexible, and organic type substrate for wireless capsule endoscopy application for 2450 MHz band. This antenna module is proposed to be wrapped over the outer wall of the capsule. Two unit antenna cells have been placed to allow orthogonal excitations, which provide better than 40 dB isolation for the entire band. Hilbert curve type fractals have been implemented here to achieve wideband profile along with size reduction feature. The individual antenna element occupies an area of 6 × 6 mm2. Liquid Crystal Polymer (LCP) is chosen as a base substrate material, which is flexible in nature. Effect of electronics on antenna performances and the detuning characteristics of radiation pattern during traversal of the capsule within the various portions of the gastrointestinal (G.I) tract has been studied analytically. Prototype antenna is tested using the homogenous type human phantom liquid. Simulated and measured results are in good agreement. Better than 15 dB impedance matching profile is observed for the entire frequency band. An equivalent electrical model for the whole system is proposed. Conclusively, various performance metrics for the efficient MIMO system are evaluated along with link budget analysis.