IEEE EMC Symp., 2001 PHASELESS NEAR-FIELD MEASUREMENTS O.M. Bucci (1) , G. D’Elia (1) , M.D. Migliore (1) , R. Pierri (2) (1) Dipartimento di Ingegneria Elettronica e delle Telecomunicazioni Universita’ di Napoli “Federico II”, via Claudio, 21. 80125 Napoli, Italy E-mail: g.delia@unina.it (2) Dipartimento di …. Seconda Universita’ di Napoli, Aversa, Italy E-mail: pierri@unina.it Abstract Near field techniques allow to estimate a 3D map of the electromagnetic emission of an equipment exploiting the knowledge of the field on a surface. However, standard near-field techniques are based on the measurement of the complex (amplitude and phase) field, while many measurement devices exploited in the framework of electromagnetic compatibility, like the spectrum analyzer, are scalar receivers. A general procedure for reconstructing the phase from only amplitude measurements, is described in this paper so that a 3D map of the electromagnetic emission from data collected by spectrum analyzers is made possible. The validity of the approach is shown by a numerical example involving a phase retrieval problem. Introduction Near-field techniques have been originally developed in the framework of advanced antenna testing techniques to reconstruct the radiated far-field pattern from near zone measurements [1]. In spite of the success of the approach in antenna testing, its use is rare in the framework of electromagnetic compatibility. However, the possibilities of such technique are by far wider than those already investigated in antenna testing, since it allows reconstructing the field at any distance from the source. As an example, near field techniques could give an accurate 3-D map of electric and magnetic field radiated or scattered by an object, thus allowing a deeper understanding of the electromagnetic emissions of electronic equipments. Moreover, these techniques could be exploited to characterize, from measurements on a single surface, the safety (volumetric) region of an antenna and thus, can be useful in characterizing a wireless base station antenna. The standard near-field approach is based on the measurement of both the amplitude and phase of the field on a scanning surface, and usually exploits a controlled measurement environment such as the anechoic chamber. Near field values are collected by means of a vector receiver, often a vector network analyzer, connected to the probe. Then, the complex data are numerically processed, usually by suitably exploiting the FFT, so that the field radiated by the antenna under test is obtained in the (either near- or far) region of interest. The extension of the near-field technique to equipment emission measurements, even if it is conceptually straightforward, is not easy in practice. In fact the standard large-band equipment used for compatibility measurements, the spectrum analyzer, is a scalar receiver, and thus, it miss any phase information, making useless any standard near-field technique. Accordingly, the availability