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POYNTING's THEOREM 159
3.4.6 Reciprocity and Antenna Radiation Pattern Measurement
a) b)
Figure 3.4.6 a) Antenna test setup in anechoic chamber, b) RAM pyramid pane
20
The simplified setup of antenna test in an anechoic (i.e. “an-echoic,” no-echo or reflecting-
free) chamber is illustrated in Figure 3.4.6a. All walls, ceiling, and floor are covered with
Figure 3.4.7 Anechoic chamber of the Ohio State University
radiation absorbent material (RAM) in the form of pyramids (see Figure 3.4.6b). The height
of pyramid absorbers depends mainly on the lowest frequency specified for the anechoic
chamber. For example, this height can reach 2m if the lowest frequency is around 30 MHz. To
block the penetration of sometimes strong interfering external signals (from local radar, TV or
radio broadcast stations, etc.) inside the chamber, all its floor-to-ceiling shielding surfaces must
be built from the highly conductive layers of steel, chicken wire, etc.
20 Public Domain Image, source: http://www.microwavejournal.com/articles/print/9839-applications-of-
time-domain-processing-in-antenna-measurements
