Tapered anechoic chamber

Abstract

The present invention includes tapered anechoic chambers and chamber systems. This invention also includes machines or electronic apparatus using these aspects of the invention. The present invention also includes methods and processes for using these devices and systems. In a preferred embodiment, a TEM antenna is utilized that is terminated by a resistive card, or R-card. This makes for a very broadband antenna that may be used to properly illuminate the test zone in a tapered chamber without changing the feed antenna. A preferred chamber utilizes an absorber layout that has never been applied to a tapered chamber, called a Chebyshev absorber layout. The concept is to place the wedge absorber tips at different heights relative to the mounting side wall and pyramidal absorber tips at different heights relative to the back wall. In this pattern, wave reflections off the pyramid tips and valleys behave very much like reflections in a multi-section transmission line. Using this Chebyshev layout around the test zone, the test zone fields will be very clean of stray signals and the polarization will be dictated by the feed horn. Also, it is then not necessary to use very thick absorber for low frequency applications, which tend to deteriorate over time. A preferred chamber also comprises a design wherein an entire tip portion of the tapered section is a separate unit. This unit is preferably designed to rotate on a system of rollers positioned between the unit and the main chamber. The result is that the polarization of the chamber can be easily changed from vertical to horizontal by simply rotating the feed structure, which can be done without disconnecting any cables to the feed.