I recently obtained the IEC 61000-4-3:2006 radiated immunity test standard which I'm trying to get geared up for. In addition to testing above 1Ghz, there are some major changes/improvements to the calibration methods. Calibration Freq Steps: In the older version of this standard, calibration was done at 10% frequency steps, but now it is 1% steps. This change is huge regarding the amount of time calibration takes. Just from 80Mhz to1Ghz with 10% it took us about 2.5 hours. At 1% steps it will take us 12 hours per power level. To do 3V/m and 10V/m will take 24 hours. To test two power levels to 6Ghz will take us over 40 hours of testing. This is considering a highly automated calibration test routine and NOT counting the time for verifying the amp saturation. I know the older version of the standard called out 10% frequency steps because 1% steps was impractical. Why did this change? Amp Saturation: In section 6.2.1, it calls out a procedure for verifying your amp is not operating in saturation. It says the difference between the two forward power levels should be within 3.1 and 5.1 db. Then is says, "If the difference is less than 3.1 db, then the amplifier is saturated and is not suitable for testing". What if the difference is greater than 5.1? Is the amp still in saturation? Fixing Saturation: So you run the procedure and you find at a few frequencies your amp is in saturation. What is the most likely cause and what do you do to fix it? Is the most likely cause the amp itself? In appendix D, the standard refers to an "adjustable/tracking/tunable low-pass filter". What is that? There is no other practical advice that I see in the standard. It explains that saturation is caused by strong harmonic signals, but what causes it if not the amp? Can it be caused by cabling, high antenna factor, or poor SWR? More specifically to my case, the power level difference for most frequencies are recorded about 5.1db, which is a 1:1 change from the amps input, which I think is a good thing. However, I have a couple frequencies that record slightly higher than 5.1db, such as 5.15 or 5.2db. Is this ok? If not, what is the cause. I also have a few frequencies at the very low end, around 80Mhz, that has a difference around 2db. I know the antenna is not very efficient down that low and the amp has to really put out a lot of power to hit 10V/m. The SWR is real bad (5:1) at these low frequencies. I understand this is common with most antennas. If this could be the cause, what can be done to fix it? (Attenuators?) Thanks everyone. The Other Brian. _________________________
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