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A Numerical Comparison of the Reflectivity of Thick-Sheet and Thin-Foil Hollow Pyramidal Absorbers

From Emerson & Cuming Microwave Products, Inc.
 

 

The reflectivity of a doubly-periodic array of hollow pyramidal absorbers (representing a typical absorber-lined wall of a large 10 m EMC test chamber) is calculated in two ways. First, a rigorous full-wave electromagnetic solver is used in the frequency range of 10 MHz to = 2 GHz. Second, an approximate ray-tracing method is used that is valid at higher frequencies (i.e. above 5 or 10 GHz). In this way a numerical comparison is made of a thick-sheet and a thin-foil hollow pyramidal absorber. Both types have sharp tips, a height of 102.7", base dimensions of 24" x 24", and a low-frequency sheet impedance of 100 O per square. Their calculated performance is very similar at low frequencies (below 500 MHz), but largely different at high frequencies (above 1 GHz). At these high frequencies the reflectivity of the thin-foil absorber appears to fully collapse, whereas the reflectivity of the thick-sheet absorber continues to improve with frequency.

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