This paper focuses on the measurement of antenna radiation patterns when fully anechoic conditions are not available and, as consequence, some undesirable echoes are initially present in the measure. Two techniques are analyzed and compared, which -starting from data measured in the frequency domain -allow the echo contributions to be identified and the antenna radiation pattern to be retrieved. The accuracy of both techniques is evaluated at the frequency of 22 GHz by comparison with measurements obtained in an anechoic chamber.

A source reconstruction technique from the measured near fields is proposed to obtain a set of equivalent currents that will characterize the forward and backward radiation patterns of an antenna. Once the equivalent sources are determined, the electromagnetic field at any aspect angle and distance from the antenna can be calculated. In this paper, the method is applied to the evaluation of the radiation from commercial antennas at any observation point. The electric field patterns of a DCS base station antenna at 1800 MHz and a horn antenna at 2500 MHz have been calculated and plotted at several distances from the antenna. This method can be used in characterizing the "reference volumes" or exclusion zones for transmitting antennas dealing with the maximum levels of electromagnetic radiation safe for human exposure, as stated in many national and international regulations.Index Terms-Antenna measurement, equivalent magnetic currents, human exposure, near-field pattern, near-field to far-field transformation, non-ionizing EM fields.

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A new model for characterizing a complex system formed by a feeding horn and a transmitarray lens is presented in this paper. This model characterizes the spillover radiation and is capable of analyzing its effect on the radiation pattern. Both the contribution of the lens and the spillover radiation are modeled as planar arrays. The proposed model shows good agreement with the results obtained in simulations using a commercial full-wave software. In addition, some features, such as the characterization of the feeding element, are included in this model, in order to improve its accuracy. Finally, the limits of applicability are also discussed throughout this paper. Thus, it is possible to set up the boundaries, in terms of F=D ratio and number of elements, within which the model is reliable.