Study of an Ingestible Antenna Detuning in a Porcine Model Ex Vivo: Methodology and Experimental Demonstration

As an ingestible antenna travels through the gastrointestinal tract, the environment surrounding the antenna continuously changes. Varying electromagnetic properties of gastrointestinal tissues (stomach, small intestine, and large intestine) lead to antenna detuning during this travel. This paper demonstrates the detuning encountered by ingestible antennas in the gastrointestinal tract with an ex vivo study in a porcine model. Four dipole antennas and a patch antenna operating at 434 MHz are used for this demonstration. The magnitude and the phase of the reflection coefficient of the antennas in different gastrointestinal tissues are measured and presented. Moreover, the results of the ex vivo study are compared with measurements conducted in homogeneous liquids mimicking the electromagnetic properties of the gastrointestinal tissues. It is shown that the differences between the magnitude and the phase values obtained in different tissues are greater in the porcine model. The results indicate the importance of performing ex vivo or in vivo characterization of ingestible antennas to validate their robustness against electromagnetic changes in the surrounding environment.