Abstract-We describe an experimental set-up for exposure of small animals to radiofrequency standing waves that allows direct measurement of the power absorbed by the animal. Essentially, the setup consists of a metallic box containing an antenna and experimental animal immobilized in a methacrylate holder; a signal generator feeding the antenna; and a power meter. In addition, the box can also contain a video camera to record the animal's behaviour, and a receiving antenna (connected externally to a power meter and a spectrum analyser) to detect undesired (external) radiation and possible harmonics of the radiating system. The absorbed power measurement trivially allows calculation of whole-body mean SAR from the animal's weight; and assuming local SARs to be proportional to whole-body mean SAR, the latter can be used to adjust organ-specific SAR predictions obtained by simulation using a commercial FDTD program with a numerical phantom. The use of the system is illustrated by application to rats given subconvulsive doses of picrotoxin to induce a seizure-prone state analogous to epilepsy: levels of the neuronal activity marker c-Fos in the frontal and piriform cortex of picrotoxin-treated rats exposed to 900 MHz GSM radiation were twice as high as those of unexposed animals.

A wide-band circularly polarized L-probe coupled patch antenna for dual-band operation," A reconfigurable patch antenna using switchable slots for circular polarization diversity," IEEE Microw. Abstract-Footprint patterns can be efficiently synthesized by means of planar arrays with hundreds or thousands of elements: an efficient combination of Woodward-Lawson and Orchard-Elliott-Stern roots optimization procedure is suggested. This hybrid technique is applied to a footprint covering Europe by using planar arrays with isotropic elements and linearly polarized circular patches. The proposed method keeps under control both the side lobe and ripple level of the synthesized pattern.Index Terms-Antenna array pattern synthesis, footprint patterns, Orchard-Elliott-Stern (OES) method, planar arrays, Woodward-Lawson (WL) method.

Non-ionizing radiation at 2.45 GHz may modify the morphology and expression of genes that codify heat shock proteins (HSP) in the thyroid gland. Diathermy is the therapeutic application of non-ionizing radiation to humans for its beneficial effects in rheumatological and musculo-skeletal pain processes. We used a diathermy model on laboratory rats subjected to maximum exposure in the left front leg, in order to study the effects of radiation on the nearby thyroid tissue. Fifty-six rats were individually exposed once or repeatedly (10 times in two weeks) for 30 min to 2.45 GHz radiation in a commercial chamber at different non-thermal specific absorption rates (SARs), which were calculated using the finite difference time domain technique. We used immunohistochemistry methods to study the expression of HSP-90 and morphological changes in thyroid gland tissues. Ninety minutes after radiation with the highest SAR, the central and peripheral follicles presented increased size and the thickness of the peripheral septa had decreased. Twenty-four hours after radiation, only peripheral follicles radiated at 12 W were found to be smaller. Peripheral follicles increased in size with repeated exposure at 3 W power. Morphological changes in the thyroid tissue may indicate a glandular response to acute or repeated stress from radiation in the hypothalamic-pituitary-thyroid axis. Further research is needed to determine if the effect of this physical agent over time may cause disease in the human thyroid gland.

In this article, we describe a mobile communications antenna consisting of concentric rings of elliptically polarized circular patches. For certain sets of relative phases, optimization of geometry and excitation amplitudes by simulated annealing synthesizes a conical beam with a maximum at a desired and satisfactory directivity within a desired range. An example of a two-ring array 50 cm in diameter with directivity 3 dB between = 35 and = 50 is presented.

In this paper, we describe the synthesis of circularTaylor-like patterns for antennas composed of concentric rings of uniformly excited elements. Optimization of the ring radii achieves close approximation to the envelope of the desired pattern within a given cone about the main beam. An alternative approach, using annular subarrays, speeds computations by limiting the number of between-ring spacings. Examples illustrate the potential of these methods.