Conceptual Analysis of Measurement on Compact Ranges

Authors: Doren W. Hess, Richard C. Johnson
Publication: 1979 Antenna Applications Symposium
Copyright Owner: NSI-MI Technologies

The testing of microwave antennas or the measurement of radar backscatter usually requires that the antenna or target under test be illuminated by a uniform plane electromagnetic wave; however, the creation of such a wave is difficult. In practice, a uniform plane wave is approximated.

The conventional procedure for approximating a uniform plane wave is to locate a transmitting source antenna at such a distance that the incident wave can be considered to be planar. When the source antenna is located 2D2/λ away from the test antenna (where D is the largest dimension of the test antenna aperture and λ is the wavelength), the spherical wavefront emitted from the source will produce a maximum phase taper of ϖ/8 at the edge of the test antenna aperture. For most applications, such a phase taper is acceptable.

In a compact range [1-5], on the other hand, the incident plane wave is created by a range reflector and feed in the immediate vicinity of the test antenna. The basic principle of operation is illustrated in Figure 1. The diverging rays from the point-source feed are collimated by the range reflector, and a plane wave is incident on the test antenna or target. The incident wave has a very flat phase front but the feed-reflector combination introduces a small (but acceptable) amplitude taper across the test zone.

The principal advantage of a compact range is its small size; this allows it to be indoors and free from adverse weather effects. In research and development laboratories, a compact range can be located convenient to the design engineers. In manufacturing or rework facilities, a compact range can be located near an assembly line for use in final testing and adjustment. By placing the range in a shielded room, one can eliminate interference from external sources and provide a test site that is secured against monitoring by outside parties.



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