The exposure of a subject in the far field of radiofrequency sources operating in the 10-900-MHz range has been studied. The electromagnetic field inside an anatomical heterogeneous model of the human body has been computed by using the finite-difference time-domain method; the corresponding temperature increase has been evaluated through an explicit finite-difference formulation of the bio-heat equation. The thermal model used, which takes into account the thermoregulatory system of the human body, has been validated through a comparison with experimental data. The results show that the peak specific absorption rate (SAR) as averaged over 10 g has about a 25-fold increase in the trunk and a 50-fold increase in the limbs with respect to the whole body averaged SAR (SARWB). The peak SAR as averaged over 1 g, instead, has a 30- to 60-fold increase in the trunk, and up to 135-fold increase in the ankles, with respect to SARWB. With reference to temperature increases, at the body resonance frequency of 40 MHz, for the ICNIRP incident power density maximum permissible value, a temperature increase of about 0.7 degrees C is obtained in the ankles muscle. The presence of the thermoregulatory system strongly limits temperature elevations, particularly in the body core.

In this paper, a complete electromagnetic and thermal analysis has been performed considering the head of a subject exposed to various kinds of cellular phones available on the market, and focusing the attention on important organs like the eye lens and brain. Attention has first been posed on a particular phone model, and a comparison between the absorbed power distribution and steady-state temperature increases has been carried out. The influence of different antennas (dipole, monopole, whip, and planar inverted F antenna) on the power absorption and on the consequent tissue heating has then been analyzed. The obtained results show, for a radiated power of 600 mW, maximum SAR values, averaged over 1 g, from 2.2 to 3.7 W/kg depending on the considered phone. The maximum temperature increases are obtained in the ear and vary from 0.22 C to 0.43 C, while the maximum temperature increases in the brain lie from 0.08 C to 0.19 C. These steady-state temperature increases are obtained after about 50 min of exposure, with a time constant of approximately 6 min. Finally, the results evidence a maximum temperature increase in the external part of the brain from 0.10 C to 0.16 C for every 1 W/kg of SAR, averaged over 1 g of brain tissue.

A new coaxial antenna for microwave ablation therapies is proposed. The antenna design includes a miniaturized choke and an arrowhead cap to facilitate antenna insertion into the tissues. Antenna matching and the shape and dimension of the area of ablated tissue (thermal lesion) obtained in ex vivo conditions are evaluated both numerically and experimentally, finding an optimal agreement between numerical and experimental data. Results show that the antenna is well matched, and that it is able to produce a thermal lesion with an average length of 6.5 cm and an average diameter of 4.5 cm in ex vivo bovine liver when irradiates 60 W for 10 min. Finally, the dependence of antenna performances on possible changes in the antenna's structure is investigated, finding an optimal stability with respect to manufacturing tolerances and highlighting the fundamental role played by the antenna's choke.

Wireless personal communication is a rapidly expanding sector, particularly in the field of cellular mobile phones and wireless local area networks (WLAN's), In an indoor WLAN system, the user of the mobile terminal can fmd himself in close proximity to the radiating antenna. It is, therefore, important to consider possible health hazards due to this type of exposure, As the most considered adverse effects of the electromagnetic (EM) fields are of thermal nature, particularly with reference to the eye, in this paper, me have evaluated the temperature increase induced in a human eye exposed to WLAN-like fields, In particular, we have considered possible WLAN's operating in the range between 6-30 GHz, so that the incident held can be simulated via a plane wave. As a first step, me have computed the specific absorption rate (SAR) distribution in a human-eye anatomical model, developed from the "visible human" data set, by using the finite-difference time-domain (FDTD) numerical technique with a cell resolution of 0.5 mm, Starting from the calculated SAR values, the heating distribution has been derived through the bioheat equation, which has been solved using an explicit finite-difference scheme, Temperature increases in the order of 0.04 OC have been calculated in the eye lens with an incident power density of 1 mW/cm(2) at 6 GHz, Lower heating is obtained in the lens when the frequency increases, Finally, considerations about the exposure limits in the considered frequency range are made

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This work tests the ability of a frequency-modulated continuous wave (FMCW) radar to measure the respiratory rate and the heartbeat of a subject in challenging indoor scenarios. To simulate a realistic configuration for ambient assisted living (AAL) applications, in which the thorax orientation towards the antenna is typically unknown, four different scenarios were considered. Measurements were performed on five volunteers positioned with the chest, left, back, and right side facing the antenna, respectively. The 5.8 GHz radar and the antennas used for the measurements were suitably designed for the considered application. To obtain a low cost and compact system, series-fed arrays were preferred over other antenna topologies. The geometry of the patches was opportunely shaped to reduce the side lobe level (SLL) and increase the bandwidth, thus ensuring good system performances. In all scenarios, the vital signs extracted from the radar signal were compared with the ones collected by a photoplethysmograph and a respiratory belt, used as references. A statistical analysis of the measured data on the different subjects and orientations was performed, showing that the radar was able to measure with high accuracy both the respiratory rate and the heartbeat in all considered configurations.

A numerically efficient way to evaluate specific absorption rate (SAR) deposition and temperature elevation inside the head of a user of a cellular phone equipped with a dual-band monopole-helix antenna is proposed. The considered antenna operates at both frequencies (900 and 1800 MHz) employed in global system for mobile communication. The results obtained show that, for a given radiated power, although the maximum SAR value as averaged over 1 g in the brain is higher at 900 MHz than at 1800 MHz, the maximum temperature increase in the brain is higher at 1800 MHz. However, taking into account that the average power levels radiated at the two operating frequencies are different (250 mW at 900 MHz and 125 mW at 1800 MHz), higher temperature elevations are obtained at 900 MHz. In this last case, the temperature increases are of the order of 0.2 degreesC in the ear, and less than 0.1 degreesC in the external brain region close to the phone. When the heating effect due to the contact of the ear and cheek with the phone is also taken into account, it is found that the predominant heating effect in the ear, able to cause temperature increases as high as 1.5 degreesC, is the one due to the phone contact, while SAR deposition plays a significant role only in the heating of the external brain region

A survey of radar systems used in the medical field is presented. First, medical applications of radars are described, and some emerging research fields are highlighted. Then, medical radars are analyzed in terms of block diagrams and behavioral equations and some implementations are shown as examples. A section is dedicated to the radiating structures used in these radars. Finally, human safety and environmental impact issues are addressed. The most investigated medical applications of radars are breast tumor diagnostics and remote monitoring of cardiorespiratory activity. New fields of interest are physiological liquid detection, and the monitoring of artery walls and vocal cord movements. Among the various topologies, continuous wave (CW) radars have been proven to yield the highest range resolution that is limited only by the system noise while the resolution of ultra wideband (UWB) and frequency modulated continuous wave (FMCW) radars is also related to the used frequency bandwidth. Concerning the maximum range, UWB radars have the best performance due to their ability to operate in the presence of environmental clutter. As for the radiating structures, planar antennas are preferred for diagnostic applications, due to their small dimensions and good matching when placed in contact with the human body. Radar systems for remote monitoring, instead, are designed by using high gain antennas and taking into account the complex radar cross section (RCS) of the body