Evaluation of systematic error of measuring object scattering diagrams caused by quasimonostatic character of measurement scheme using irradiator’s assembly sets in anechoic chamber of collimator type

Abstract

The main factors causing the occurrence of systematic errors in measuring the backscatter patterns of targets when using irradiator assemblies in collimator type radar measuring complexes are considered. It is shown that the implementation of a quasimonostatic measurement scheme with a bistatic angle determined by spatial separation of the phase centers of irradiators assembly is the most significant factor in the experimental determination of the backscattering characteristics of reflectors with highlighted directed properties, to which the monostatic-bistatic equivalence theorem is not applicable. To quantify the influence of this factor, it is proposed to use indicators characterizing the decrease of the maximum and average recorded cross-section of trihedral corner reflectors within the main lobe of the backscatter diagram, determined by the half power level. The listed indicators do not take into account the non-flatness of the phase surface of the probe field, however, they can be considered as reasonably justified lower bounds for systematic measurement errors for each irradiators assembly. Using the mathematical modeling, mono- and bistatic cross-section diagrams of trihedral corner reflectors of various wave sizes with different face shapes were calculated, error estimation for their backscattering diagrams were determined using a set of irradiator assemblies. Ratios are obtained for estimating of width of the lobe of the bistatic scattering indicatrix at the level of –3 dB of trihedral corner reflectors with triangular, radial, and square face shapes, and a recommendation on the rational choice of the working frequency of the assembly when implementing large-scale electrodynamic modeling is made.