Study Of Near-Field Measurement Methold For The Determination Of Monostatic RCS Of Targets

Near-field measurement method has many advantages, such as lage information quantity obtained, conveniently measurements indoor, high measurement precision, good confidentiality, all-weather operation. Consequently, this method of measurement plays a very important role in the research field of scattering characteristics about target or antenna at home and abroad. In this paper, the transformation formulas of near-field to far-field are obtained by theoretical analysis so that the relationship between near-field scattering and far-field scattering is built and the monostatic near-field scattering measurement method of the three-dimensional target and antenna is studied by computer simulation. The main work of this paper are as follows:Firstly, the algorithm of near-field to far-field transformation theory is studied, including descending dimensional algorithm and three-dimensional algorithm. Based on electromagnetic theory and combined with special functions, the mathematical relationship between the scattered near-field and the far-field RCS of targets or antennas is built.Secondly, the far-field radiation characteristic of microstrip antenna is studied by using descending dimensional algorithm of near-field to far-field transformation theory. Antenna scattering field always is composed of structural mode scattering field and mode scattering field.is difficult to decide. Both antenna structural mode RCS and mode RCS are calculated by descending dimensional algorithm of near-field to far-field transformation theory and separating theory of antenna scattering And antenna structural mode RCS compared with structural mode RCS calculated directly.Thirdly, based on three-dimensional algorithm of near-field to far-field transformation theory, monostatic near-field scattering measurement method is studied by means of electromagnetic simulation software FEKO. In the simulated measurements, above of all, the electric dispole with the horizontal and vertical polarization is utilized as a "single-transmit single-receive" probe to perform monostatic near-field scattering measurement and obtain monostatic scattered near-field data of the three-dimensional target, the far-field monostatic RCS of the target is obtained by near-field to far-field transformation theory and compared with monostatic RCS simulated directly by FEKO. The calculation results confirm the applicability of the method used in 3-D target.Finally, the factors of producing error in the monostatic near-field scattering measurement method are analysed and compensation technique of error is studied. At the same time, it confirms that sampling theorem is scientific.