Miniaturized Quad-Band Implantable Antenna for Wireless Capsule Endoscopy and Deep Tissue Monitoring Applications

Miniaturized multiband antennas are essential components of implantable biomedical devices (IMDs), enabling them to perform multiple tasks simultaneously in different biomedical applications. This study proposes a highly miniaturized implantable antenna with quad-band characteristics. The implantable antenna’s volume is $6\times 6\times 0.6$ mm. The proposed antenna operates in the Medical Implant Communication System (MICS) band (401–406 MHz), Wireless Medical Telemetry Service (WMTS) (1427–1432 MHz), and industrial, scientific, and medical (ISM) bands (433.1–434.8 MHz, 902–928 MHz, and 2400–2483.5 MHz) for multitasking, such as data telemetry, wireless power transfer, and control signaling. This design achieves miniaturization using meandered lines, eliminating the need for shortening vias or ground plane slots, typically employed in implantable antennas for size reduction. This arrangement simplifies the structure and minimizes back radiation, enhancing overall performance. The proposed antenna was thoroughly analyzed through simulations integrated into a wireless capsule endoscopy (WCE) device. A fabricated prototype embedded in minced pork was experimentally validated, demonstrating excellent agreement with the simulated parameters. The presented antenna exhibits a measured −10 dB bandwidth of 76.8, 72, 125, and 215.4 MHz at 402/433, 915, 1410, and 2450 MHz, respectively. Furthermore, it maintains stable measured gains of −44.7, −34, −30.6, and −29.7 dBi across the respective bands of interest. Specific absorption rates (SARs) in heterogeneous stomach tissues were evaluated at the four resonance frequencies to ensure human safety, showing compliance with the IEEE standards. Furthermore, to evaluate the range of effective communication, a link budget analysis was performed at data rates of 1, 12, and 78 Mb/s, demonstrating a minimum effective transmission range of 4.7 m. These features make the proposed miniaturized implantable antenna suitable for various biomedical applications.