OVERVIEW

The limited size of indoor chambers precludes the measurement of large test objects under protective cover, yet the need to collect RCS data in such an environment persists. Impelled by requirements to measure the RCS characteristics of large airframe components, such as those found in the Stealth Bomber and the Advanced Tactical Aircraft, at least two large airframe manufacturers built compact ranges of unprecedented size in the late 1980s. Despite the perceived need for these kinds of measurements, however, one of the two was unable to exploit its investment in these capabilities. With insufficient internal projects to support its compact range, McDonnell Douglas attempted to peddle its facility in the early 1990s to any and all customers who could afford the $12 500 shift charge for eight hours of chamber use [1]. Whether the marketing scheme was successful or not, the facility and its capabilities were impressive.

The design objective in the compact range is to collimate a beam of diverging rays into a system of parallel rays, thereby satisfying the phase-error minimization discussed in Chapter 4. Given the relatively short distance available in an indoor chamber, there are only two ways to do this. One is to insert a dielectric lens between the antenna and the target, and the other is to bounce the antenna beam off a large metal reflector toward the target. Because it is easier to build a large reflector than a large lens, all contemporary compact ranges use reflectors. Lest we deny the...