Stochastic sources localization algorithm based on near-field two-point planar scanning data
Radio engineering. Electronics. Telecommunication systems
Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia
The important problem that is considerable through the electromagnetic compatibility (EMC) analysis is to determine the spatial-frequency distribution of the device under test (DUT) radiation in both the near and far field. This is similar to one of the antenna systems analysis problem where the antenna directivity and gain should be determined with high accuracy. The conventional solution of both problems is provided by the frequency domain measurements of the complex amplitudes for each frequency at different space points. This procedure can be carried out both in the far field and near field with some modifications. At the same time, near-field measurements provide better accuracy and reduce the measurement setup requirements. On the other hand near field measurements allow a direct computation of the far field in a limited sector of space angles. The proportions of the sector for planar measurement scenario depend on the object and measurement plane dimensions as well as the distance between them. In accordance with the equivalence principle  the DUT may be replaced with a set of electric or magnetic dipoles. This simple dipole model allows analyzing the radiation pattern in the wider space region. The proposed technique for the estimation of spatial-frequency DUT radiation can be implemented by using the identification of the dipole model parameters based on the near-field measurement.
The presented approach can be also effectively used in EMI analysis problem. However, the EMI fields radiated by complex devices are often random. Then, the described procedure may be performed for the cross-correlation characteristics of the stochastic field sources.
In this work, the author proposes a parametric identification procedure for stochastic EMI sources localization based on two-point time-domain planar scanning in the near field region of the radiation structure. As a model of a radiating structure, the set of electrical dipoles arranged on a grid in object plane is proposed. Some simplifications of the two-point scanning measurement setup are introduced for two typical cases of mutually correlated sources. The improvement of the EMI sources space resolution is achieved by the application of the proposed parametric identification procedure, which includes the model order selection by using the information criterion and model parameters designation with the parametric spectral estimation method. An example of equivalent effective sources spatial localization inside the real complex device based on the simulation and measurement results is presented.
Keywords:dipole model, near-field, stochastic field, two-point scanning, correlation spectra, parametric identification
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