Wireless Capsule Endoscopy Using Backscatter Communication

A small and efficient antenna is designed and manufactured for operating inside the human intestine. The antenna is used for radio frequency (RF) backscatter communication in which the antenna radar cross section (RCS) is altered using an active micro-watt switch. The switching mechanism modulates the incident wave transmitted from an external reader system, and the capsule data is transferred to the reader. Thus the active transmitter is removed from the implant and several 10s of mW power is saved. The power saving can realize real-time, and high data rate video streaming for improved visualization of the gastrointestinal tract. The implanted antenna is a conformal meander line with capacitive feed mechanism and provides dual-polar radiation to compensate for the capsule orientations in the gastric tract. The antenna design considers the specific environment of the biological tissues and provides a self-resonant geometry for high reflectivity. Bi-static backscatter method is used for the on-body reader antennas in the UHF band. The backscatter communication feasibility is demonstrated using numerical computations and experimentally validated in a liquid phantom and in-vivo animal experiments.