Multidimensional Spatial Filtration for Improving Measurement Accuracy of Electrodynamic Characteristics of Antenna Radiation

The problem of reducing the measurement errors of the electrodynamic characteristics of antenna radiation using measuring systems in the far zone is considered. 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 errors and the need to use complexes of other types. A method is proposed to improve the accuracy of measurements of antenna radiation patterns in the Fresnel zone under conditions of multipath multiple reflections. The method under consideration can be used to expand the range of antennas tested using far-field measuring systems. The implementation of the method can significantly reduce the requirements for the characteristics of measuring systems and, therefore, reduce the cost of testing antenna devices and systems. 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 restoration of the distributions of equivalent fields on the plane or in the volume containing the test antenna or its geometric projection onto the plane of rotation. The decrease in the error caused by the multipath propagation of the electromagnetic field occurs due to the filtering of the synthesized spatial impulse response of the antenna from the signals due to multiple reflections outside the allocated volume. The linearity of the transformations used allows the possibility of recalculating the synthesized characteristic to an arbitrary distance. Thus, it is possible to restore the radiation pattern in the Fraunhofer zone and to reduce the error caused by the sphericity of the phase front of the electromagnetic field. A feature of the proposed method is a significant increase in the signal-to-noise ratio. The main theoretical relationships and the results of experimental studies on testing the method are presented.