Packaging and Integration of a Dual-Polarized MIMO Antenna with Pattern Diversity for Dual-Camera Wireless Capsule Endoscopy.

Abstract

Dual-camera wireless capsule endoscopy improves diagnostic coverage of the gastrointestinal tract but introduces severe constraints on antenna placement, electromagnetic coupling, and in-body communication reliability. This paper presents a compact, camera-integrated, four-element dual-polarized multiple-input multiple-output (MIMO) antenna specifically designed for dual-camera capsule endoscopy operating at 868 MHz. The proposed architecture consists of two planar, dual-polarized MIMO antenna modules co-located with opposing cameras, enabling complementary polarization and radiation-pattern diversity to mitigate orientation-dependent fading in lossy biological environments. Each antenna element employs a slot-loaded half-annular patch structure to achieve $\pm$ 45° linear polarization while maintaining stable impedance under tissue loading. The integrated antenna occupies 61.84 mm² and achieves inter-element isolation exceeding 23 dB, envelope correlation coefficients below 0.03, and diversity gain above 9.9 dB. Experimental validation in tissue-mimicking phantoms demonstrates a measured realized gain of -33.7 dBi per element, robust impedance stability across gastrointestinal tissues, and a link margin exceeding 20 dB. Specific absorption rate analysis confirms compliance with IEEE safety limits at power levels well above those used in practical capsule endoscopy systems. The proposed camera-aware antenna integration provides a compact and reliable solution for next-generation dual-camera capsule endoscopy, supporting robust in-body wireless telemetry under unpredictable orientation and propagation conditions.