The solid, pyramidal or wedge shaped, carbon-loaded polyurethane foam absorber is most probably the first RF absorber technology manufactured on an industrial scale. In the 1950s, polyurethane foam was found to be a good carrier for the conductive solution and the pyramidal shaped absorber came into being.

 

design

Of all known absorbers, carbon-loaded polyurethane foam absorbers provide the highest broadband performance at both normal incidence and at wide incidence angles. The solid, pyramidal or wedge shaped absorbers, with their excellent performance at microwave frequencies, are the preferred solution for Antenna, RCS, Compact Range and EW anechoic chambers. The absorbers are available in a variety of thicknesses, enabling the chamber designer the opportunity to choose grades appropriate for specific frequencies and incidence angles.

 

For very large EMC chambers, performing beyond the requirements of the normal standards, Albatross Projects uses a resistive hollow pyramidal technology with outstanding reflection coefficient from 30MHz up to 40GHz (typically –25dB till –55dB).

 

Fire redundancy is a critical consideration in the design of resistive foam absorber. The NRL suffix refers to its compliance with the fire retardant requirements of the U.S. Naval Research laboratory (NRL) test 8093.

 

Albatross Projects uses for all absorbers a modular fixation means, i.e. the “plate and rail” for larger absorbers and the VELCRO method for smaller sizes.

 

Example of “plate and rail” installation. Backing plate bonded to the absorber back.

data pyramidal absorbers

Standard Colour light blue
Base size (cm) 61 x 61
Maximum service temperature 90°C
Power handling capability 1.5 kW/m²
Fire retardancy DIN 4102 Class B2
ISO 11925-2
NRL 8093 Tests 1, 2 & 3

 

 

The table below indicates the most important physical data of the various grades of solid pyramidal foam absorbers.

 

 

 

Eccosorb VHP grade Total height A (cm) Pyramid Height, B (cm) Pyramid width, C (cm) Base height, D (cm)

Number of Pyramids, per piece

Nominal Weight, (kg)
VHP-2-NRL 5.6 4 1.9 1.6 1,024 1.2
VHP-4-NRL 10.2 7.7 3.8 2.5 256 1.3
VHP-8-NRL 20.3 17.8 6.8 2.5 81 1.6
VHP-12-NRL 30.5 27.8 10.2 2.7 36 2.2
VHP-18-NRL 45.7 41.7 15.3 4 16 2.9
VHP-26-NRL 66.0 55.9 20.3 10.2 9 5.4
VHP-36-NRL 91.4 76.4 30.5 15 4 6.3
VHP-45-NRL 114 93.7 30.5 20.3 4 9

 

The table below indicates normal incidence reflectivity of the various grades of solid pyramidal foam absorbers at various frequencies.

 

Guaranteed Maximum reflectivity of ECCOSORB® VHP Grades
120MHz 200MHz 300MHz 500MHz 1GHz 3GHz 5GHz 10GHz 15GHz 24GHz
VHP-2-NRL –30 –40 –45 –50
VHP-4-NRL –30 –40 –45 –50 –50
VHP-8-NRL –30 –40 –50 –50 –50 –50
VHP-12-NRL –25 –35 –40 –50 –50 –50 –50
VHP-18-NRL –30 –40 –45 –50 –50 –50 –50
VHP-26-NRL –25 –35 –40 –50 –50 –50 –50 –50
VHP-36-NRL –20 –30 –35 –45 –50 –50 –50 –50 –50
VHP-45-NRL –20 –25 –35 –40 –45 –50 –50 –50 –50 –50

data wedge absorbers

standard colour light blue
Base size (cm) 61 x 61/122 x 20.3
Maximum service temperature 90°C
power handling capability 1.5 kW/m²
Fire retardancy DIN 4102 Class B2
ISO 11925-2
NRL 8093 Tests 1,2 & 3

 

 

 

Total height A (cm) Wedge height B (cm) Wedge width C (cm) Base height D (cm) Total lenght E (cm) Total width F (cm) Number of wedges per piece Nominal weight (kg)
ECCOSORB WG-4 12.7 8.3 6.8 4.4 61.0 61.0 9 1.9
ECCOSORB WG-8 20.3 15.2 10.2 5.1 61.0 61.0 6 2.5
ECCOSORB WG-12 30.5 24.1 10.2 6.4 122.0 20.3 2
ECCOSORB WG-20 50.8 43.4 20.3 7.4 122.0 20.3 1 3.5
ECCOSORB WG-26 66.0 55.8 20.3 10.2 122.0 20.3 1 5.3

 

 

For further information, please contact us.

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