Contents I. Introduction
PARABOLIC reflectors are commonly used in compact ranges to generate the desired plane wave to illuminate the object under test in RCS and antenna pattern measurement systems [1]. The stray signals emanating from the reflector edges interfere with this desired plane wave and, consequently, corrupt the fields in the test zone, causing measurement errors [2]. Unfortunately, these stray signals arrive in the test zone at almost the same time as the desired plane wave and cannot be time gated. Serrated edges [3], [4] and blended rolled edges [5]–[8] are widely used to overcome the discontinuity of the sharp reflector knife edge and reduce the field variations in the test zone. A performance tradeoff study [3] has shown the superiority of the blended rolled edges over the triangular serrated edges, even for very well-designed reflectors. However, the preferred performance of the blended rolled edge reflectors is accompanied by its higher manufacturing cost. To potentially overcome this problem, an edge treatment is presented in this paper that greatly reduces the cost. Resistive sheets (R-cards) can serve as fences that block/attenuate the reflector edge diffraction and protect the test zone from severe stray signals. Currently, these R-cards can be obtained in large quantities at a very reasonable cost. Because the R-card edge treatment proposed here does not deal with the reflector structure, its cost is very low. Furthermore, the R-card fences can be added to existing reflectors with “old-fashioned” treatment such that an improvement in the measurement accuracy can be obtained. The concept and validation of this R-card fence design is presented in the present paper.
