N. P. Balabukha – Ph.D. (Eng.), Associate Professor, Head of Laboratory, Institute of Theoretical and Applied Electrodynamics of RAS
N. L. Men’shikh – Post-graduate Student, Moscow Institute of Physics and Technology; Engineer, Institute of Theoretical and Applied Electrodynamics of RAS
V. S. Solosin – Ph.D. (Phys.-Math.), Leading Research Scientist, Institute of Theoretical and Applied Electrodynamics of RAS
This paper presents calculation of the field distribution in the quiet zone of the tapered anechoic chamber (AEC) operating in the fre-quency range from 100 MHz to 1 GHz.
Computer model of a tapered AEC is created. In this model radio-absorbing material is replaced by a dielectric layer with a given ref-lectance. Electrodynamical calculation is carried out by the rigorous method using FEKO.
Tapered part of the chamber is 15 m in length. This part of the chamber is covered with wedge RAM. A source of radiation is placed in the vertex of the chamber. The hyperbolic lens is located in the aperture of the taper. The lens has following characteristics: focal length is 17 m, diameter is 4 m, and dielectric permittivity is 1,6. A object is placed in the part rectangular of the chamber with the 8,3 × 8,3 m cross section and 10 m in length. This part of AEC is covered with pyramidal RAM. The quiet zone of the tapered AEC is a horizontal cylinder 3 m in diameter and 4 m in length and its center is placed at the distance of 4 m from aperture of the taper part.
Results of the electrodynamical analysis showed that in frequency range 100 MHz – 1 GHz for the tapered AEC the non-uniformity of the field in the quit zone 3 m in diameter does not exceed ±1,5 dB, and the phase of the non-uniformity is no more than ±8°. Using the lens suggested minimize of phase of the non-uniformity over the entire operating frequency range. Herewith the non-uniformity of the field is somewhat increased in comparison with the field distribution in the chamber without lenses on 1–1,5 dB for the corresponding frequency. At low frequencies (100 MHz), the lens is almost no impact on the field after that. At frequencies of 400 MHz and 800 MHz, the non-uniformity of the field distribution is mainly caused by the diffraction at the lens edges. The comparison of the calculation by rigorous method and the calculation of physical optics confirms this fact.
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