A single-fed miniaturized circularly polarized microstrip patch antenna is designed and experimentally demonstrated for industrial-scientific-medical (2.4-2.48 GHz) biomedical applications. The proposed antenna is designed by utilizing the capacitive loading on the radiator. Compared with the initial topology of the proposed antenna, the so-called square patch antenna with a center-square slot, the proposed method has the advantage of good size reduction and good polarization purity. The footprint of the proposed antenna is 10×10×1.27 mm3. The simulated impedance, axial ratio, and radiation pattern are studied and compared in two simulation models: cubic skin phantom and Gustav voxel human body. The effect of different body phantoms is discussed to evaluate the sensitivity of the proposed antenna. The effect of coaxial cable is also discussed. Two typical approaches to address the biocompatibility issue for practical applications are reported as well. The simulated and measured impedance bandwidths in cubic skin phantom are 7.7% and 10.2%, respectively. The performance of the communication link between the implanted CP antenna and the external antenna is also presented.

Capacitively Loaded Circularly Polarized Implantable Patch Antenna for ISM Band Biomedical Applications

Wireless capsule endoscopy

The design procedure, realization and measurements of an implantable radiator for telemetry applications are presented. First, free space analysis allows the choice of the antenna typology with reduced computation time. Subsequently the antenna, inserted in a body phantom, is designed to take into account all the necessary electronic components, power supply and bio-compatible insulation so as to realize a complete implantable device. The conformal design has suitable dimensions for subcutaneous implantation (10 × 32.1 mm). The effect of different body phantoms is discussed. The radiator works in both the Medical Device Radiocommunication Service (MedRadio, 401-406 MHz) and the Industrial, Scientific and Medical (ISM, 2.4-2.5 GHz) bands. Simulated maximum gains attain -28.8 and - 18.5 dBi in the two desired frequency ranges, respectively, when the radiator is implanted subcutaneously in a homogenous cylindrical body phantom (80 × 110 mm) with muscle equivalent dielectric properties. Three antennas are realized and characterized in order to improve simulation calibration, electromagnetic performance, and to validate the repeatability of the manufacturing process. Measurements are also presented and a good correspondence with theoretical predictions is registered.

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Design, Realization and Measurements of a Miniature Antenna for Implantable Wireless Communication Systems

Wireless medical telemetry permits the measurement of physiological signals at a distance through wireless technologies. One of the latest applications is in the field of implantable and ingestible medical devices (IIMDs) with integrated antennas for wireless radiofrequency (RF) communication (telemetry) with exterior monitoring/control equipment. Implantable medical devices (MDs) perform an expanding variety of diagnostic and therapeutic functions, while ingestible MDs receive significant attention in gastrointestinal endoscopy. Design of such wireless IIMD telemetry systems is highly intriguing and deals with issues related to: operation frequency selection, electronics and powering, antenna design and performance, and modeling of the wireless channel. In this paper, we attempt to comparatively review the current status and challenges of IIMDs with wireless telemetry functionalities. Full solutions of commercial IIMDs are also recorded. The objective is to provide a comprehensive reference for scientists and developers in the field, while indicating directions for future research.

Implantable and ingestible medical devices with wireless telemetry functionalities: a review of current status and challenges.

An implantable rectenna, which consists of a planar inverted-F antenna (PIFA) and a rectifier circuit, is proposed for far-field wireless power transfer. The PIFA has a folded ground plane to miniaturize its size. The performance of the wireless power link between the implanted antenna and an external antenna is examined. A method of adding a parasitic patch over the human body is used to enhance the wireless power link, thus to increase the received power level. Safety considerations of far-field RF powering are discussed. The RF-to-DC conversion circuit efficiency is optimized after the receiver power level of the implantable antenna is estimated based on the safety considerations. Finally, a rectifier circuit and an integrated rectenna solution are discussed.

Design and Safety Considerations of an Implantable Rectenna for Far-Field Wireless Power Transfer

This paper investigates a conformal antenna for the ingestible bio-telemetric capsule system. This system has the potential to provide real-time biological information from within the human body via a radio frequency link. The balanced planar meandered dipole (concept used for antenna miniaturization through space-filling) is discussed along with the offset planar meandered dipole, which facilitates better matching. The conformal chandelier meandered dipole antenna (CCMDA), which is an extension of the offset planar meandered dipole and envelopes the capsule surface, is then investigated. The return loss, input impedance, and radiation pattern characteristics of the CCMDA are discussed in detail at the operating frequency of 1.4 GHz. Additionally, electrical components (specifically the batteries) are modeled inside the capsule to investigate their effects on the conformal antenna performance in free space. The capsule antenna is then inserted into a simple box model (a simplification of the human torso) and a 4-mm precision human-body model (Ansoft) where the detuning effects are observed and discussed. Finally, a circularly polarized receiver antenna design consisting of orthogonal dipoles is suggested which provides polarization diversity and is miniaturized to fit into a personal digital assistant (PDA) for portability of the data telemetric link.

Conformal Ingestible Capsule Antenna: A Novel Chandelier Meandered Design

This paper presents a novel ingestible capsule antenna, the conformal chandelier meandered dipole antenna (CCMDA), as a practical and effective design for bio-telemetry. The CCMDA is a conformal version of the offset planar meandered dipole antenna (OPMDA). The similarities in performance between the two antennas are presented through simulations. The CCMDA is further investigated and through simulation, it is shown to have inherent advantages due to its conformal geometry, which allows for tightly packed electrical components within the capsule, and polarization diversity that enables a communication link, which is not strongly sensitive to the orientation of the capsule within the human body. The capsule antenna is then simulated within a 4 mm precision human-body model (Ansoft) where the detuning effects along with the polarization and radiation pattern are investigated and discussed.

Ingestible capsule antenna for bio-telemetry

The conformal capsule antenna possesses attractive features like conformal geometry, miniaturized size, polarization diversity, omni-directional pattern similar to dipole, easy and straightforward tuning ability to compensate the effects of electrical components inside the capsule and human body which makes it a good candidate for capsule imager.

Phillip Izdebski

Papers

Conformal Ingestible Capsule Antenna: A Novel Chandelier Meandered Design

Ingestible capsule antenna for bio-telemetry

A miniaturized ingestible antenna for capsule medical imaging system