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A method for accurate determination of electromagnetic fields around the Worldwide Interoperability for Microwave Access (WiMAX) base stations (BSs) is developed in this paper. The influence of the characteristics of the WiMAX signal on the settings and parameters of the spectrum analyzer (SA) used for exposure assessment is investigated. Optimal settings of the SA are proposed, and the results obtained using simulations and measurements agree very well. A practical application in the neighborhood of a WiMAX BS is performed. The obtained electric field values correspond very well for the different settings and are compared with the reference levels for the general public and those for occupational exposure. The results of this paper can be used for practical measurement procedures of the exposure due to WiMAX signals. Index Terms--802.16-2004, electromagnetic measurement, electromagnetic radiation, exposure assessment, spectrum analyzer (SA), Worldwide Interoperability for Microwave Access (WiMAX).

In this paper, the scattering parameters of two dipoles placed closely to a flat, homogeneous, biological tissue are characterized in the 2.4-GHz band. The impact of the presence of a flat phantom and of the height of a dipole above the phantom on the reflection coefficient is analyzed through measurements and simulations. The effect of the type of tissue on the reflection coefficient is also investigated by performing simulations for a range of relative permittivity and conductivity combinations spanning the whole range of human tissues at 2.4 GHz. A semiempirical path loss model, validated by measurements and simulations, is presented for wireless communication, for antenna heights from 2 mm up to 5 cm and antenna separations from 10 to 50 cm. Also, the influence of the relative permittivity and conductivity on the path loss is modeled, leading to a range of possible values and lower and upper boundaries for the path loss as a function of the antenna height. The combination of the range with the boundaries results in a best-case and worst-case path loss model for wireless body area networks. The models are validated with measurements on the torso of a human. Index Terms--Dipole antenna, homogeneous flat phantom, path loss, scattering parameters, wireless body area network (WBAN).

A low-cost measurement method for the extraction of the relative phases of the field of base station and broadcast antennas is presented. Our purpose is to determine the polarization of the field at a measurement site using magnitude measurements only. By determining six amplitude components using a spectrum analyzer, the polarization ellipse of the field can be obtained. This low-cost method can be used for outdoor measurements, which is not possible with network analyzers. Using this method and thus knowing the polarization of the incident field we are able to determine more accurately the actual electromagnetic power absorbed in people at a measurement site. Index Terms--Base station antenna, electromagnetic field, measurement, measurement probe, phase extraction, polarization, specific absorption rate (SAR), telecommunication and broadcast antenna.

A comparison between the safety distances of a base station antenna using electromagnetic field and the specific absorption rate (SAR) assessment is made. The input power in the antenna is determined such that the electromagnetic fields and the SAR equal the reference levels and the basic restrictions, respectively, at a certain distance. Up to about 10 W the localized SAR delivers the largest safety distances when the electric field averaged in a volume is considered. This means that from 10 W and up the SAR does not need to be determined to obtain the largest safety distances. Safety distances based on the SAR will be smaller than those obtained from the electromagnetic fields when the maximum field value in a plane is considered. Index Terms--Base station antenna, electromagnetic field, measurement, occupational exposure, rectangular box phantom, safety distance, specific absorption rate (SAR), time-domain filtering.

In this paper, the influence of the measurement probe on the evaluation of the far and near field of an electromagnetic source is characterized. While measuring, the electromagnetic field will be disturbed by the measurement probes themselves. Therefore, not the true, free-space field but the disturbed field will be measured. The disturbance can not be fully taken into account by the calibration, especially in the near field. It is found that in the near field, these disturbances are much higher than in the far field for a large sensitive measurement probe. This paper will show that when the disturbance must be limited to a predefined value (e.g., 5%), a suitable measurement probe with maximum sensitivity can be selected. The characterization was performed using a numerical electromagnetic computational program. Index Terms--Antenna, calibration, disturbance, electromagnetic field.