The facts about Hybrid Absorbers
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An unbiased data sheet
Ferrite tiles work on what is known as ‘magnetic permeability’ and function very well at lower frequencies where the wavelength is too long for normal resistive pyramidal absorbers to work in any useable degree.
Commercially available ferrite tiles have a useable (>-15dB) return loss performance in the range of 30-800MHz, at 1GHz the optimum performance (in normal incidence) is c-13dB, the performance above 1GHz decays with frequency increase.
To extend the functional range of the ferrite tile a Hybrid pyramidal absorber system is often used.
The ferrite tiles are designed to be exposed to free space (377 ohm) but when this is disturbed by placing materials front of the ferrite then the ferrite tile performance is modified.
The overall performance of the composite system (ferrite + hybrid) tends to make the ferrite performance worse at 30-800MHz but greatly increases the overall performance above 800MHz.
Note - The performance of this composite system is not enough for such applications as antenna measurement chambers and other high performance high frequency applications.
The objective of the hybrid absorber is to make the anechoic performance enough to satisfy EMC and military applications with broadband requirements.
If this composite system works very well above 1GHz then the ferrite tile performance will be reduced in lower frequencies, conversely if the low frequency performance is high then the 1GHz+ performance is likely to be low.
There are several types of Hybrid absorber:
