Meandering Pattern 433 MHz Antennas for Ingestible Capsules

Michael J Christoe,Shaghik Atakaramians,Jialuo Han,Aron Michael,Kourosh Kalantar-Zadeh,Natthaporn Phaoseree

doi:10.1109/access.2021.3092068

Michael J Christoe, Shaghik Atakaramians + Show 4 more

Open Access

https://doi.org/10.1109/access.2021.3092068

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Abstract

A number of design challenges are associated with in-body devices, especially ingestible capsules, including selection of operation frequency and antenna design. Operation frequency, miniaturization, gain, and interference with the environment and the internal components of ingestible capsules are all challenging factors. In this work, we design and measure the performance of miniature antennas that can be included in ingestible capsules. The meandering pattern designs are implemented with a 433 MHz center frequency which is within one of the industrial, scientific and medical (ISM) bands. The antenna patterns are rolled into cylinders to reflect their configuration inside a capsule. The effects of different antenna design features, environmental dielectric changes, and the battery locations relative to the antenna traces are explored. We show that the optimized antenna can offer acceptable performance even when the center frequency shifts due to the modulation of the dielectric constant of the media and by the insertion of batteries. Both simulations and measurements provide insight into how the meandering antenna should be designed for the desired frequency that can be expanded to other ingestible and implantable systems.

Highlights

Ingestible capsules are becoming more prevalent as medical devices [1-16]
After using ferrites in the measurements, two main troughs remain in S11 patterns for each antenna: one is in the 400-500 MHz range and the other is in the 800-900 MHz range, which in essence are the first and second harmonics of the antenna, respectively
The return loss parameters were analysed through the simulations and measurements of the antennas immersed in neutral water, saline water, and ballistic gel with a consideration of battery positions

Summary

Introduction

Ingestible capsules are becoming more prevalent as medical devices [1-16]. the reliability of their communications systems is still challenging. The capsule size and shape are limited due to the need to adhere to the typical ingestible capsule dimensions (such as dimensions used by Medtronic, Olympus, IntroMedic, Jinshan Science and Technology, and CapsoVision for their capsules [18]), which limits the available space within the capsule, imposing constraints on the dimensions of the antenna and restricting the possibility of making it larger to obtain higher gains. Another issue for the antenna is relevant to the components that are placed inside the capsule. The batteries especially have critical impact on the antenna characteristics as they occupy a significant amount of the volume in the capsule, can be in close proximity to the antenna, and are metallic

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Conclusion