Is it required to correct for the 6 dB attenuator in the CI calibration?

Discussion and questions regarding the Radiated Immunity and Conducted Immunity modules of RadiMation.
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incognito
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Joined: 03 Feb 2012, 13:07

Is it required to correct for the 6 dB attenuator in the CI calibration?

Post by incognito »

We are performing a Conducted Immunity calibration according 61000-4-6.
We included a 6 dB attenuator between the amplifier and the injection device.

The question is if I have to add this into Radimation.
There is no calculation anywhere as this is in the injection part, right?
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joro
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Re: Is it required to correct for the 6 dB attenuator in the CI calibration?

Post by joro »

It is theoretically correct to configure an attenuator and have RadiMation correct for the 6dB attenuation. However it is not necessary at all, because the same test setup is used during the calibration and the real subtitution test. The 6 dB attenuator is not used for the measurement of an actual value, and thus the correcting or not correcting of it in RadiMation is not influencing the measurement results.

This is because during the CI calibration there will be levelled on the test level in the injection device, while the generated forward power out of the amplifier is being recorded.
When the actual test is performed, RadiMation will use the calibration data to regulate and repeat the output power in order to create the correct test level again. As long as the 6 dB attenuator is present during the calibration and the real subsitution test, the correct test level is generated during the test. The standard does require that the same 6 dB attenuator is used during calibration and the test.

The only accurate absolute value that is required during a conducted immunity calibration is the powerlevel that is measured at the output of the calibration jig. The actual power value that is present on that location determines the test-level that is being calibrated (and tested). As long as all the other parts of the setup (forward power meter, 6 dB attenuator, cabling, injection device, etc...) are all the same in the test as they where during the calibration, it is ensured that the generated test-level during the test is the correct testlevel.

It is important to have a 6 dB atenuator between the amplifier and the injection device (to prevent standing waves and bad impedances of the injection device to the amplifier). However the attenuation of that attenuator isn't required for the correctness of the levelling of the test-level. And thus it is not necessary to correct for the attenuator in software.
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