Antenna Specific Absorption Rate Research Articles

Design of a Compact Circularly Polarized Implantable Antenna for Capsule Endoscopy Systems.

This research proposes a miniature circular polarization antenna used in a wireless capsule endoscopy system at 2.45 GHz for industrial, scientific, and medical bands. We propose a method of cutting a chamfer rectangular slot on a circular radiation patch and introducing a curved radiation structure into the centerline position of the chamfer rectangular slot, while a short-circuit probe is added to achieve miniaturization. Therefore, we significantly reduced the size of the antenna and made it exhibit circularly polarized radiation characteristics. A cross-slot is cut in the GND to enable the antenna to better cover the operating band while being able to meet the complex human environment. The effective axis ratio bandwidth is 120 MHz (2.38-2.50 GHz). Its size is π × 0.032λ02 × 0.007λ0 (where λ0 is the free-space wavelength of at 2.4 GHz). In addition, the effect of different organs such as muscle, stomach, small intestine, and big intestine on the antenna when it was embedded into the wireless capsule endoscopy (WCE) system was further discussed, and the results proved that the WCE system has better robustness in different organs. The antenna's specific absorption rate can follow the IEEE Standard Safety Guidelines (IEEE C95.1-1999). A prototype is fabricated and measured. The experimental results are consistent with the simulation results.

A dual wide-band ingestible antenna design for wireless capsule endoscopy

In this paper, we present a dual wide-band ingestible antenna design for wireless capsule endoscopy (WCE) biotelemetry applications. The design process employs Characteristic Mode Analysis (CMA) and driven modal analysis. The effectiveness of the prototype antenna is afterward assessed through measurements using a tissue-equivalent phantom liquid model. We investigate the effects of antenna implantation depth and capsule shell thickness on its performance, providing insights into practical considerations. The proposed dual-band antenna demonstrates good performance in both the 1.4 GHz Wireless Medical Telemetry Services (WMTS) and 2.45 GHz Industrial, Scientific, and Medical (ISM) bands, exhibiting measured impedance bandwidths of 36% and 22%, respectively. The measured peak realized gains are −22.9 dBi and −25.3 dBi for the WMTS and ISM bands, respectively, with a compact footprint of 78.5 mm2. To ensure health and safety and optimal performance, we evaluate the antenna's specific absorption rate (SAR) and link margin (LM). Additionally, we assess the performance of the proposed antenna in comparison with the state-of-the-art design for capsule antennas in WCE applications.

A triple-band spiral-shaped antenna for high data rate fully passive implantable devices

A spiral-shape, multi-band and compact antenna for healthcare and high-speed biomedical devices is presented. It operates simultaneously at 2.4/5.8 GHz of the industrial scientific medical (ISM) band and 4.8 GHz as the first-band harmonic. Therefore, it is suitable for fully-passive in-body systems. The compact size of the designed antenna is 9.2 × 9.2 × 0.5 mm3 and shorting pins are not used to reduce the dimensions. The results have been checked by full wave software in both three-layer and one-layer phantoms with different body tissues. The presented antenna has been embedded in two implantable systems and integrated with other components to evaluate real working scenarios. In addition, for safety study and numerical analysis of radiation absorption per unit mass of human tissue, the antenna specific absorption rate (SAR) has been analyzed. The designed antenna has been implanted in a muscle liquid phantom and parameters were evaluated experimentally. The proposed antenna exhibits multi-band characteristics, has a via-less and simple configuration, a compact size, low SAR, and suitable gain value making it a proper and applicable choice for implantable passive devices.

A Compact On/Off-Body Dual Band Antenna with Modified Ground for Healthcare Applications

ABSTRACT In this paper, a compact dual-band radiator with a modified ground structure is presented for on/off body communication. The antenna is capable of resonating in the ISM-I (2.4 GHz) and WLAN (5.15–5.85 GHz) bands. The proposed antenna consists of a novel compact ring loaded with a C-shaped radiator for dual-band operation. To improve impedance matching and shifting of the lower band at the ISM-I band, a modified ground structure is used. This suggested antenna has a small footprint of 0.24λ0×0.22λ0×0.016λ0, wherever λ0 is the free space wavelength at the lower operational frequency. The proposed antenna is parametrically studied, as well as the analysis of electric field and SAR at different positions on the arm are also carried out to check its utility for medical applications. The proposed antenna's specific absorption rate (SAR) meets IEEE standards and the prototype's measured findings validate the simulation's results.

A stable miniaturised AMC loaded flexible monopole antenna for ingestible applications

This paper proposes an ultra-miniaturised, flexible 5.8 GHz antenna to give better performance for an ingestible wireless capsule endoscopy system. The use of an artificial magnetic conductor (AMC) unit cell in this design helps in enhancing the gain, improving the efficiency and reducing the size at resonance. This novel AMC-based layer is modelled as a radiator, and is excited by a complementary strip feed. The proposed design is printed on a flexible polyimide material of size 4.6 × 7.6 × 0.15 mm, with dielectric constant 3.5 and loss tangent 0.008. The antenna has an omni-directional radiation pattern with gain 1.64 dBi. The size is reduced drastically by bending the structure to fit inside a standard-sized ingestible capsule of 26 × 11 mm. The performance metrics of the antenna after placing inside the wireless ingestible capsule are presented with the help of an analysis of the reflection coefficient curves, radiation pattern, specific absorption rate (SAR) and field distributions. In addition, different positions and orientations of the antenna and different bending conditions are used, and these cases are solved using our AMC-based unit cell radiator. We carry out simulations using High Frequency Structure Simulator (HFSS) and measurements are made by immersing the fabricated antenna in minced meat. The results of this novel structure are compared with those of other ingestible antennas proposed in the literature. The proposed design has a SAR value of 0.82505 W/kg at around 5.8 GHz over 1 g of tissue, thereby redirecting the radiation away from the human body. This conformal AMC structure achieved better miniaturisation while maintaining the antenna resonance and SAR within permissible limits.

P.436 Cognitive function in alcohol dependent patients after six months of out-patient treatment

This paper proposes an ultra-miniaturised, flexible 5.8 GHz antenna to give better performance for an ingestible wireless capsule endoscopy system. The use of an artificial magnetic conductor (AMC) unit cell in this design helps in enhancing the gain, improving the efficiency and reducing the size at resonance. This novel AMC-based layer is modelled as a radiator, and is excited by a complementary strip feed. The proposed design is printed on a flexible polyimide material of size 4.6 × 7.6 × 0.15 mm, with dielectric constant 3.5 and loss tangent 0.008. The antenna has an omni-directional radiation pattern with gain 1.64 dBi. The size is reduced drastically by bending the structure to fit inside a standard-sized ingestible capsule of 26 × 11 mm. The performance metrics of the antenna after placing inside the wireless ingestible capsule are presented with the help of an analysis of the reflection coefficient curves, radiation pattern, specific absorption rate (SAR) and field distributions. In addition, different positions and orientations of the antenna and different bending conditions are used, and these cases are solved using our AMC-based unit cell radiator. We carry out simulations using High Frequency Structure Simulator (HFSS) and measurements are made by immersing the fabricated antenna in minced meat. The results of this novel structure are compared with those of other ingestible antennas proposed in the literature. The proposed design has a SAR value of 0.82505 W/kg at around 5.8 GHz over 1 g of tissue, thereby redirecting the radiation away from the human body. This conformal AMC structure achieved better miniaturisation while maintaining the antenna resonance and SAR within permissible limits.

Antenna Design and SAR Analysis on Human Head Phantom Simulation for Future Clinical Applications.

BackgroundThe rapid development of a variety of devices that emit Radiofrequency Electromagnetic fields (RF-EMF) has sparked growing interest in their interaction with biological systems and the beneficial effects on human health. As a result, investigations have been driven by the potential for therapeutic applications, as well as concern for any possible negative health implications of these EM energies [1-4]. Recent results have indicated specific tuning of experimental and clinical RF exposure may lead to their clinical application toward beneficial health outcomes [5].MethodIn the current study, a mathematical and computer simulation model to analyze a specific RF-EMF exposure on a human head model was developed. Impetus for this research was derived from results of our previous experiments which revealed that Repeated Electromagnetic Field Stimulation (REMFS) decreased the toxic levels of beta amyloid (Aβ) in neuronal cells, thereby suggesting a new potential therapeutic strategy for the treatment of Alzheimer's disease (AD). Throughout development of the proposed device, experimental variables such as the EM frequency range, specific absorption rate (SAR), penetration depth, and innate properties of different tissues have been carefully considered.ResultsRF-EMF exposure to the human head phantom was performed utilizing a Yagi-Uda antenna type possessing high gain (in the order of 10 dbs) at a frequency of 64 MHz and SAR of 0.6 W/Kg. In order to maximize the EM power transmission in one direction, directors were placed in front of the driven element and reflectors were placed behind the driven element. So as to strategically direct the EM field into the center of the brain tissue, while providing field linearity, our analysis considered the field distribution for one versus four antennas. Within the provided dimensions of a typical human brain, results of the Bioheat equation within COMSOL Multiphysics version 5.2a software demonstrated less than a 1 m˚K increase from the absorbed EM power.

Enhancing antenna performance and SAR reduction by a conductive composite loaded with carbon-silica hybrid filler

In this paper, we describe a technique for reducing the specific absorption rate (SAR) and human effects on antenna performance, based on combined use of rubber conductive composite loaded with carbon-silica hybrid filler used like a single director and a resonant half wave dipole. The finite-difference time-domain method was used to evaluate SAR and antenna performance for different antenna-composite configurations and distances. Bandwidth, gain, and radiation efficiency for different antenna-composite configurations were compared. It was found that the presence of a conductive composite loaded with carbon-silica hybrid filler can effectively reduce maximum SAR value (up to 70%) in a human head model, increasing the radiation efficiency (up to 67%) and the bandwidth (up to 110%) of the antenna.

The Contrast of Two Kinds of Microwave Antenna SAR Simulation

Abst r a c t. Specific Absorption Rate (SAR) represents the electromagnetic radiation sorption ability of the biological organisms. It is a hotspot issue in thermal ablation. Different antenna structure can get the different SAR in clinical treatment. This study use simulation software HFSS which based on finite element method simulate the SAR of two microwave antenna (ETW antenna and Cap-Choke microwave antenna). Obtain the curves of SAR distribution, predict the temperature field more accuracy and provide method to design microwave antenna. The ratio of the long axis and short axis of Cap-Choke antenna is about 3:2, while the ratio of ETW antenna is 4.7:1.7. So Cap-Choke antenna is suitable for the ablation of tumor, while ETW antenna can meet to the requirement of linear ablation area in atrial fibrillation ablation therapy.

Correlating Threshold Power With Free-Space Bandwidth for Low-Directivity Antennas

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper develops a threshold power rationale that can be used to demonstrate inherent compliance for portable wireless devices with specific absorption rate (SAR) limits over the 300–6000-MHz frequency range. This is achieved first by understanding the relationship between basic antenna parameters (bandwidth, operating frequency, and distance to the body) and SAR. From this, an upper limit is determined for the power transmitted by a portable wireless device such that the SAR will not exceed the compliance limit. Based on the presented computational and measured data, an empirical formula is developed for the threshold power as a function of the aforementioned parameters. It is demonstrated that the derived threshold power is conservative for all of the low-directivity antennas studied. Computed results are also compared against practical device data (mobile telephone data collected from the manufacturers) to show that the predicted threshold power data using the proposed formula are conservative. The limitations of the proposed formula are also discussed. </para>