Search

The paper introduces numerical and experimental investigations of biotelemetry radio channels and wave attenuation in human subjects with ingested wireless implants. The study covers commonly used frequencies in telemedicine applications: ultrahigh frequencies at 402 MHz, 868 MHz and the industrial, scientific and medical (ISM) band frequency at 2.4 GHz. Numerical electromagnetic analysis is applied to model in/on-body radio propagation channels and the resulted parameters demonstrated the importance of digital phantom accuracy in characterization of wave absorption and attenuation with regards to organ contents, specifically for the digestion system, Path gain variations of biotelemetry radio channels, in the close vicinity of the subject, with wireless implants were measured using a near field scanner. Simulation results were verified with measurement in good agreement. [ABSTRACT FROM AUTHOR]

In this paper, an analysis of radio channel characteristics for single- and multiple-antenna bodyworn systems for use in body-to-body communications is presented. The work was based on an extensive measurement campaign conducted at 2.45 GHz representative of an indoor sweep and search scenario for fire and rescue personnel. Using maximum-likelihood estimation in conjunction with the Akaike information criterion (AIC), five candidate probability distributions were investigated and from these the κ - μ distribution was found to best describe small-scale fading observed in the body-to-body channels. Additional channel parameters such as autocorrelation and the cross-correlation coefficient between fading signal envelopes were also analyzed. Low cross correlation and small differences in mean signal levels between potential dual-branch diversity receivers suggested that the prospect of successfully implementing diversity in this type application is extremely good. Moreover, using selection combination, maximal ratio, and equal gain combining, up to 8.69-dB diversity gain can be made available when four spatially separated antennas are used at the receiver. Additional improvements in the combined envelopes through lower level crossing rates and fade durations at low signal levels were also observed. [ABSTRACT FROM AUTHOR]

Implantable devices have been investigated with great interest as communication tools. These implantable devices are embedded into the human or pet body. The vital information (such as temperature, blood pressure, cardiac beat, etc.) can be transmitted from implantable devices to the external equipment by use of a wireless communication link. Therefore, the research on the antenna for implantable devices (implanted antennas) is very important. This paper proposes an implanted H-shaped cavity slot antenna for short-range wireless communications. This type of antenna, which is designed to operate at the industrial-scientific-medical band (2.45 GHz), is investigated by using finite-difference time-domain calculation. We analyzed the performances of the proposed antenna which is embedded into the human body between the shoulder and the elbow. However, since the proposed antenna is too small to fabricate, a scale model is adopted for antenna measurements. Some characteristics of the scale model of the antenna are also calculated and measured by using the 2/3 muscle-equivalent phantom. The results show that the proposed antenna has promise for use in an implant. [ABSTRACT FROM AUTHOR]

Bioimplantable sensors using radio-frequency telemetry links that enable the continuous monitoring and recording of physiological data are receiving a great deal of attention. The objective of this paper is to study the feasibility of an implantable sensor for tissue characterization. This has been done by querying an LC sensor surrounded by dispersive tissues by an external antenna. The resonant frequency of the sensor is monitored by measuring the input impedance of the antenna, and correlated to the desired quantities. Using an equivalent circuit model of the sensor that accounts for the properties of the encapsulating tissue, analytical expressions have been developed for the extraction of the tissue permittivity and conductivity. Finally, experimental validation has been performed with a telemetry link that consists of a loop antenna and a fabricated LC sensor immersed in single and multiple dispersive phantom materials. [ABSTRACT FROM AUTHOR]

This paper presents a four-channel telemetric microsystem featuring on-chip alternating current amplification, direct current baseline stabilization, clock generation, time-division multiplexing, and wireless frequency-modulation transmission of microvolt- and millivolt-range input biopotentials in the very high frequency band of 94-98 MHz over a distance of ∼ 0.5 m. It consists of a 4.84-mm² integrated circuit, fabricated using a 1.5-µm double-poly double-metal n-well standard complementary metal-oxide semiconductor process, interfaced with only three off-chip components on a custom-designed printed-circuit board that measures 1.7 × 1.2 × 0.16 cm³, and weighs 1.1 g including two miniature 1.5-V batteries. We characterize the microsystem performance, operating in a truly wireless fashion in single-channel and multichannel operation modes, via extensive benchtop and in vitro tests in saline utilizing two different micromachined neural recording microelectrodes, while dissipating ∼ 2.2 mW from a 3-V power supply. Moreover, we demonstrate successful wireless in vivo recording of spontaneous neural activity at 96.2 MHz from the auditory cortex of an awake marmoset monkey at several transmission distances ranging from 10 to 50 cm with signal-to-noise ratios in the range of 8.4-9.5 dB. [ABSTRACT FROM AUTHOR]

Biotelemetric systems, especially those that employ implanted devices, work with inductive links, where usually large circular external coils are separated by relatively large distances (dimensions of centimeters) from the small/Millimeter- or submillimeter-size) implanted coils. This paper shows that order these conditions, a simplified method for calculation of the mutual (M) between the coils, avoiding elliptic integrals, can be obtained. A procedure for coil design, with maximum M between them, is also described. [ABSTRACT FROM AUTHOR]

On-body area ultrawideband (UWB) communication is of high importance for promising new biomedical applications. However, there are currently few measurements or models describing on-body area propagation channels which put an emphasis on various body postures, Using the frequency-dependent finite-difference time domain (FDTD) method and a realistic human body model, we simulate various body postures for modeling on-body channels. Based on the FDTD numerical results, we derive an on-body propagation model and determine the model parameters for some representative transmission links on the human body. A good match is obtained between the data derived from FDTD and the statistically implemented models in terms of key communication metrics. In addition, for the chest-to-right-waist transmission link, an experiment is performed in order to verify the results from the FDTD method, and it is found that the model parameters agree well between the two approaches. [ABSTRACT FROM AUTHOR]

We report the experimental in situ characterization of 30-40 MHz and 868 MHz wireless transmission schemes for ingestible capsules, in porcine carcasses. This includes a detailed study of the performance of a magnetically coupled near-field very high-frequency (VHF) transmission scheme that requires only one eighth of the volume and one quarter of the power consumption of existing 868-MHz solutions. Our in situ measurements tested the performance of four different capsules specially constructed for this study (two variants of each transmission scheme), in two scenarios. One mimicked the performance of a body-worn receiving coil, while the other allowed the characterization of the direction-dependent signal attenuation due to losses in the surrounding tissue. We found that the magnetically coupled near-field VHF telemetry scheme presents an attractive option for future, miniturized ingestible capsules for medical applications. [ABSTRACT FROM AUTHOR]