Absorber with optimized low frequency reflection

An absorber with optimized low frequency reflection comprising:

• a twisted pyramid having a flat base side, a first length (11) and a first pair of permittivity coefficients (e1' and e1"),
• a first layer adjacent the base side of the pyramid and having a second length (12), and a second pair of coefficients (e2' and e2"), and
• a second layer adjacent the first layer and having a third length (13) and a third pair of permittivity coefficients (e3' and e3"),
• said absorber being characterized in that the first length (11) is equal to 2.20 m (+/- 1 cm), the second length (12) is equal to 0.188 m (+/- 1 cm, the third length (13) is equal to 0.302 m (+/- 1 cm), and
• e1'=10 E (-0.370 LogF+1.005)(+/- 10%)
• e1"=-10 E (-0.484 LogF+1.012)(+/- 10%)
• e2'=10 E (-0.353 LogF+1.317)(+/- 10%)
• e2"=-10 E (-0.222 LogF+0.789)(+/- 10%)
• e3'=10 E (-0.316 LogF+1.785)(+/- 10%)
• e3"=-10 E (-0.598 LogF+2.347)(+/- 10%)
• in the range 30-150 Mhz, wherein permittivity is a complex function of the form e'+ie" where e' is a real value and e" is an imaginary value and e1', e2' and e3' are real values of permittivity measured at the frequency F megahertz and e1", e2" and e3" are imaginary values of permittivity measured at the frequency F megahertz.