Absorber Assembly for an Anechoic Chamber

Abstract

An electromagnetic absorber assembly (10) capable of minimizing reflectivity caused by reflected and diffracted waves within a test chamber (1) is presented. The absorber assembly (1) includes a plurality of first wedges (11) and a plurality of second wedges (11) disposed in a symmetrical arrangement so as to form a continuous and smoothly changing v-shaped pattern along one or more walls (5-7) of an anechoic test chamber (1). Each wedge (11) has a triangular-shaped first end (26) and second end (27) formed by a pair of side walls (16, 18, or 19) and a base wall (17). One second end (27) of each first wedge (11) contacts and covers one first end (26) of each second wedge (11) along a contact plane (15). First and second wedges (11) are disposed at a first angle (46) and a second angle (47), respectively, about the contact plane (15) in a symmetrical arrangement. The assemblies described could be installed on a flat or shaped absorber base (44) or wall (20) to divert reflected and refracted fields away from a quiet zone (3). Interplay between the shaped absorber base (44) or wall (20) and intersecting wedges (11) facilitates minimization of clutter and secondary scattering.

Description

1. TECHNICAL FIELD[0001]The invention generally relates to a device which minimizes reflectivity caused by reflected and diffracted waves within a test chamber. Specifically, the invention is a wave absorber assembly comprising a plurality of first wedge-shaped absorbers and a plurality of second wedge-shaped absorbers which are disposed so as to form a continuous and smoothly changing v-shaped pattern along the interior surface of planar or non-planar walls of an anechoic chamber. The arrangement of v-shaped absorbers improves control over reflectivity within a chamber so as to better control primary and secondary scattering effects which in turn improves quiet zone reflectivity and reduces quiet zone clutter.2. BACKGROUND ART[0002]A typical anechoic chamber for electromagnetic compatibility (EMC), far-field (FF) antenna, or radar cross section (RCS) measurements includes a metallic enclosure with internal surfaces covered by an absorbing material. An anechoic chamber also contains...

AI Technical Summary

Benefits of technology

[0013]An object of the present invention is to provide an absorber assembly which accounts not only for wall specular reflections, but also for the primary and secondary scattered fields caused by diffraction within an anechoic chamber so as to better control the reflected fields and direct them away from the quiet zone during EMC and antenna measurements and from the quiet zone and source during RCS measurements.

[0015]Several advantages are offered by the invention. The invention minimizes the level of test zone reflectivity, so as to facilitate a larger test zone. The invention extends test zone performance to include lower frequencies than otherwise achievable with similarly dimensioned anechoic chambers of conventional design. The invention minimizes chamber size and volume for a given minimum level of reflectivity and test zone size, thereby lowering chamber implementation costs. The invention is based upon Geometrical Optics and Geometrical Theory of Diffraction, so as to account not only for specular reflections, but also for the overall combined diffraction of waves from a wedge. The invention facilitates a plurality of solutions within a chamber so as to optimize reflectivity and control the path of diffracted waves within all scattered fields.

Problems solved by technology

For large aperture antennas operating at higher frequencies, this distance is very large.

However, the level of reflections from walls, floor, and ceiling increases with chamber length, thus offsetting the benefit of separation distance in many applications.

However, reflections from the chamber enclosure, even when covered by an absorbing material, negatively contribute to the uniformity of illumination within the test zone.

The echo signals via indirect paths are often reflected from the walls of the chamber, and as such could contaminate measurements when not removed.

Neither absorbing material nor time range gating is capable of completely removing or eliminating all unwanted echo signals.

As such, some unwanted signals ultimately arrive back at the source antenna at approximately the same time as the return from the device under test, thus establishing the chamber background clutter level which limits the lowest RCS signal measurable.

Accordingly, all presently known applications of absorbers within a test chamber do not adequately control the reflection and scattering of electromagnetic waves.

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