Yu. I. Belov, I. A. Illarionov, E. L. Varentzov

The paper presents the measurement results of the open-end rectangular waveguide antenna radiation pattern (in operating fre-quency range of the standard 7.2 mm×3.4 mm). The antenna is placed above the conductive disc flange of diameter which is much more than the operating wavelength, for various distances between the antenna aperture and the flange. Thus it is a technique to study the impact of conductive objects to the open end waveguide (OW) radiation patterns, for example, the mounting flange behind the probes of the near field - far field measurement setups, or the surface of various vehicles transporting the broad beam antennas for special intents. Also an effect of the absorbing materials covering the OW antenna-s supporting constructions of the near field - far field measurement setups to be compared with the free space probe antenna patterns has been studied. To explain the experimental results been obtained in the study, the semi-empirical model has been developed for the rectangular OW radiation pattern in presence of perfect conductive flange placed behind the probe aperture. Thus the developed model and computer simulation confirm that the reason of the OW antenna radiation field and its gain distortions in operating frequency range is an interference of the field component, proportional to structural component of the field scattered by the antenna, and the component of the field radiated by the antenna in the aperture radiation theory approximation. The measurement results are in good conscience with the antenna gain distribution been evaluated with the developed OW and flange radiation model at the broad operating frequency range. Finally, the semi-empirical model OW with flange radiation pattern presents the evaluated functions, which are used to accelerate the antenna calibration process, and it is very useful for wide and ultra wide antenna measurements.