Wireless Capsule Endoscopy Antennas: Tissue-Robust Design, Capsule Integration, and Experimental Evidence

Wireless capsule endoscopy (WCE) antennas operate under challenging electromagnetic conditions due to variations in gastrointestinal tissue properties, capsule orientation, and coupling with internal electronic components. These factors influence impedance matching, radiation efficiency, and signal propagation, making reliable communication difficult to establish from isolated antenna measurements. This critical review examines recent advances in compact and conformal antennas, polarization and pattern diversity, multiple-input–multiple-output (MIMO) configurations, reconfigurable structures, and optical–RF integration, with particular emphasis on tissue-dependent performance and practical capsule constraints. Published designs are critically examined in terms of radiation characteristics, installed efficiency, specific absorption rate (SAR), receiver configuration, and experimental validation. A four-level evidence framework is proposed to distinguish numerical investigations, phantom-based measurements, integrated telemetry experiments, and in-vivo evaluations. The comparative assessment highlights how differences in anatomical models, antenna integration, and measurement conditions limit direct comparisons of reported performance. Particular attention is given to the distinction between favorable antenna characteristics and demonstrated wireless communication reliability. Based on these findings, a structured validation approach is presented to support more consistent performance assessment and guide the development of reliable antenna systems for future wireless capsule endoscopy applications.