Multidimensional spatial filtering to improve the antennas electrodynamic characteristics measurements accuracy

The article describes the problem of reducing the measurement uncertainties of the electrodynamic characteristics of antenna radiation using the far-field measuring systems. The most significant limitations in such measurements are the sphericity of the phase front and multipath reflections. The impossibility of ensuring the specified conditions can lead to unacceptable measurement uncertainties and to the need of using another measurement system’s type. A method is proposed for increasing the accuracy of measuring antenna radiation patterns in the Fresnel zone under conditions of multipath reflections. The considered method can expand the nomenclature of antennas tested by the far-field measuring systems. The use of this method can significantly reduce the requirements for the characteristics of measuring systems and, therefore, reduce the cost of antenna testing. The essence of the proposed method is to synthesize the spatial (two- or three-dimensional) impulse response of the antenna by transforming the original frequency-angular dependence of the transmission coefficient. The physical meaning of the transformation can be interpreted as the reconstruction of the equivalent field distributions containing the test antenna or its geometric projection onto the rotation plane. The reducing of uncertainty caused by the multipath propagation of the electromagnetic field achieves by the filtering of the synthesized antenna spatial impulse response from the signals outside of the allocated volume. The used transformations linearity allows the possibility of recalculating the synthesized characteristic to an arbitrary distance. Thus, it is possible to reconstruct the antenna pattern in the Fraunhofer region and reduce the uncertainty caused by the electromagnetic field wavefront sphericity. The feature of the proposed method is the significant signal-to-noise ratio increase. The main theoretical relations and the results of experimental studies on testing the method are presented in this article.

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