FAQ/Emission
This page contains all the Frequently Asked Questions related to Radiated Emission and Conducted Emission module of RadiMation®
Contents
- 1 How does a G-TEM compare to an anechoic chamber?
- 2 Auto attenuator is going to 10 dB even with low emission values
- 3 Why is there a big drop between the value during and after a G-tem measurement?
- 4 I do not have an automated mechanical clamp mover, can I still perform the clamp mover test?
- 5 How can I export the values in the graph to the clipboard?
- 6 Can the order of the final measurement of peaks be specified?
- 7 I have found a problem. What should I do?
- 8 I have another question, that is not answered yet
How does a G-TEM compare to an anechoic chamber?
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!
Auto attenuator is going to 10 dB even with low emission values
When auto attenuation is selected, RadiMation® sends a command to the receiver or analyser to select auto attenuation. The attenuation that will be selected by the receiver or analyser is then depending on the used measurement device itself. When an analyser is used, it can help to decrease the reference level to for example 50 dbuV. Verify if the attenuator has been decreased at the lower reference level setting. A lot of analysers can only use a 0 dB attenuation value, if the reference level is lower or equal to -20 dbm (or 87 dBuV).
Why is there a big drop between the value during and after a G-tem measurement?
For a G-tem measurement you need to change the EUT to all three axis (X,Y and Z). During the measurement of one side you will see the emission coming out of that side. After measuring all three side the G-tem correction to the OATS can be applied, including the normalised site attenuation. For frequencies smaller then 1 Ghz this can mean that the total value is lower then the measured on one side. For example the attenuation for a horizontal 3 meter site at 30 MHz is 15.8. For the horizontal 10 meter site at 30 MHz this is 29.8. See the standard for the rest of the values.
I do not have an automated mechanical clamp mover, can I still perform the clamp mover test?
If you have a none automated mechanical clamp mover, select the manual clamp mover for driving the clamp mover. When RadiMation wants to move the clamp the user will be notified with a message box to which distance the clamp needs to be placed.
How can I export the values in the graph to the clipboard?
Exporting the numbers can be done by following this procedure:
- left click the graph with the mouse
- press the 'x' key on the keyboard
- Select text / data only
- press export
- press export again
Can the order of the final measurement of peaks be specified?
When in a Multiband Emission test, the "Measure Peaks" button is pressed, all the peaks in the list will get measured. The order in which the peaks are measured in the final measurement is not predetermined. It could indeed be, that the order is going from the highest peak number to the lowest peak number. It is currently not possible to change this order in which the peaks are measured. The most ideal solution, is to have the peaks measured in the order that needs the least movement of the antenna tower and turntable. Also any test-site changes should be reduced to a minimum. The easiest solution is that the configured change-order is used to also determine the order of the final measurements. That is however currently not the case. This request for additional functionality is already registered as: #2409: Change order specified in a multiband emission test is not used during final measurement of peaks
I have found a problem. What should I do?
If you have found a problem in the RadiMation® software, it is best to report it to us (for example through this online form). We will categorize the reported issue, register it in our defect database, and investigate the problem. When a workaround or solution is available, we will report this back to you.
I have another question, that is not answered yet
Just submit your question on RadiMation® forum or the online web-form. And we will give you an answer.
