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Antenna Diagnostics and Measurement Postprocessing Using Equivalent Source Technique
This paper discusses recent advances in processing of measured field data. The technique is based on the extraction of equivalent sources on a 3D closed surface enclosing the antenna under test (AUT) from near or far field measured radiation patterns, which allows malfunction detection and design improvements, investigation of abnormalities in antenna measurements, removal of unwanted radiation caused by spurious effects besides the more conventional near field to far field and near field to near field transformations. The methodology proposed is based on the equivalence theorem, which allows substituting the AUT by a set of equivalent sources lying on an enclosing surface. The main advantage of this formulation over the wave expansion technique is its geometry-independence, in principle being able to accommodate efficiently for atypical geometries both for the radiator and the measurement range (including truncated versions of canonical ranges). This follows from the observation that the formulation in terms of equivalent sources involves characteristic functions which are specific to the geometry and discretization of the radiator and the measurement range and even the accuracy of source-field computation (on the other hand, these are known a priori through analytical expressions in wave expansion techniques). The features of the method are illustrated with application examples.
