FAQ/Emission
This page contains all kind of Frequently Asked Questions related to RadiMation®
How does a G-TEM compare to an anechoic chamber?[edit]
A G-TEM cell is in principle not an accepted (full compliant) EMC test environment and compared to an anechoic chamber the cables will be routed and placed differently.
Sometimes the error at higher frequencies becomes smaller through the band. This is what normally is expected in case of correlation measurements between a small G-TEM in relation to a large Anechoic chamber or OATS (due to near field effects smaller test rooms will have larger deviations at low frequencies).
Beside this, one should realize that even full compliant radiated emission measurements still have relatively high measurement uncertainties. To give you some concrete figures:
- The absolute accuracy for an OATS measurement (including all uncertainties of equipment, site attenuation and antenna factor) are about +/- 5 dB.
- For emission measurements in anechoic chambers this figure is about +/- 6 dB for a SAR and even +/- 10 to 20 dB for a FAR.
So one can imagine that you can expect even higher uncertainties in a (G)TEM cell
Generally when comparing two sites with each other it is important to make the correct calculations for both uncertainties (root sum of the squares). So if both sites have 5 dB uncertainty (which is not feasible with a TEM cell) the total expected difference will be maximum 7 dB. In other words a measured 10 dB difference is not even bad at all!