Enhanced compact range reflector concept using an R-card fence: two-dimensional case

Compact range reflector edge diffraction can be reduced by using an R-card fence. Well-designed R-cards (resistive sheets) placed in front of reflector edges reduce the field variations in the test zone. The keys to successful R-card design are proper choices of both the geometry and resistance profile. In this paper, a two-dimensional (2-D) version of the problem is attacked to show the basic concepts and essential considerations in designing R-cards. The complexity of a design is simplified by separating the different mechanisms associated with R-cards. Undesired mechanisms can be visualized by ray tracing and then eliminated by choosing the correct R-card geometry. The useful impact of this treatment is illustrated as it controls the transmitted energy level through the R-card; thus, the resistance of the R-card is defined based on an optimum aperture taper. Excellent performance in both the cross-range and down-range directions is presented, and the validity of the design is verified over a wide band of frequencies. The simplicity, flexibility, and low cost of this R-card fence concept provides a viable alternative to other edge treatments.