Ultrawideband Conformal MIMO Antenna With Ferrite-Based Modified Inverted-F Structure for Wireless Capsule Endoscopy Applications

This paper presents an ultra-wideband (UWB) conformal multiple-input-multiple-output (MIMO) antenna for wireless capsule endoscopy (WCE) and deep tissue monitoring. The design innovatively integrates a toroidal ferrite substrate with a modified inverted-F structure to achieve a bandwidth of 120.5% (0.31-1.25 GHz) by exciting and manipulating multiple modes, covering industrial, scientific, and medical (ISM) bands (433/915 MHz). The antenna, with an unfolded size of 28.27×5×1.5 mm3, is designed to facilitate integrate with capsule components such as batteries and camera. Experimentally verified, the design achieves measured gains of -14.1/-13 dBi at 433/915 MHz in minced pork and an isolation level greater than 33 dB between elements. Specific absorption rate (SAR) values comply with biocompatibility standards, while MIMO performance metrics (ECC < 0.001, DG > 9.99 dB) meet communication requirements. This work provides a high-performance solution for sub-GHz in-body high-definition medical imaging transmission.