Ferrite tiles have a usable performance range of 30-1000MHz, actually the optimum band is more like 30-800MHz with diminishing performance towards 1000MHz.
Most modern EMC test anechoic chambers need to operate above 1000MHz and for this reason we offer the hybrid absorber which is used in conjunction with ferrite tile.
The Global EMC GDS-H system enhances the upper frequency performance of the ferrite tiles without sever degradation of the ferrite tile performance at low frequencies.
The pyramidal hybrid absorbers have to give reasonable return loss above 1GHz so that in a chamber the emissions (CISPR16 SVSWR) and the immunity EN/IEC61000.4.3 are met.
The hybrid pyramidal absorber works on progressive impedance, this is achieved by resistive material and mass (size), it is better to have lower dielectric content and greater mass (larger absorbers) but smaller absorbers do work in smaller chambers:
The main hybrid absorbers can be 500mm~600mm deep
The main absorber should be 800mm~1000mm deep
Global EMC have a method of optimising the performance of each chamber to guarantee compliance to the EMC regulations.
The Global EMC pyramidal hybrid can be truncated with polystyrene tiles.
