Ultra-Miniaturized In-Band Full-Duplex Implantable Antenna for Wireless Capsule Endoscopy

This study introduces a novel in-band full-duplex implantable antenna designed for Wireless Capsule Endoscopy (WCE) and operating at the 2.45 GHz Industrial, Scientific, and Medical (ISM) band. The antenna is simulated inside a human body phantom with a depth of 50 mm. The antenna's size is kept ultra-miniaturized $(\pi\times(3)^{2}\times 0.254=7.17\ \text{mm}^{3})$ through the integration of multiple semi-circular slots and shorting pins. The antenna exhibits a nearly omnidirectional radiation pattern at both 2.45 GHz for port 1 and port 2, attaining gains of -44.5 dBi at port 1 and -46.2 dBi at port 2. Achieving higher than 25 dB isolation between the two antenna ports is made possible by using a very thin superstrate and substrate, along with the addition of a middle slot in the ground plane. Thanks to its high isolation, small size, and simultaneous transmit and receive capability, this antenna is found to be suitable for WCE applications.