Compact In-Band Full-Duplex Implantable Antenna for Wireless Capsule Endoscopy

This study presents an ultraminiaturized implantable in-band full-duplex (IBFD) antenna, designed for wireless capsule endoscopy (WCE) applications. Through the integration of semicircular slots and shorting pins, the antenna achieves a small volume of 7.17 mm3 (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pi \times $ </tex-math></inline-formula> (3 mm)<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{2} \times 0.254$ </tex-math></inline-formula> mm), surpassing the state-of-the-art in compactness. Simulations of the proposed design are conducted within a human body phantom to demonstrate the antenna’s operation at 2.45 GHz. Radiation patterns from both ports are nearly omnidirectional, and an isolation level of greater than 28 dB is achieved. Our results indicate that the antenna can establish reliable wireless communication over distances exceeding 8 m, with a 10-dB margin at both ports. The specific absorption rate (SAR) values at 2.45 GHz are found to be 29.7 W/kg at 1 W input power. Experimental validation using minced pork demonstrated a good agreement with simulation results.