Hello all,
I am working with a CXA 9000B with all options enabled. In particular, while using as an EMI receiver for EMC pre-compliance, I face issues with Dynamic range. PFA photographs to compare the results of Keysight and R&S EMI receiver.
Queries-
- For identical settings of Dwell time (MT for R&S), RBW and frequency step size; the lower and higher values of signal detected by R&S is large [Dynamic range].
- With LISN factor of 10dB defined for R&S LISN [Keysight aint got one, third party not available]- only DC offset of 10dB was introduced. Signal shifted upwards and coincided with R&S signal, but what about the lower picks?
- What is the dynamic range for CXA9000B with EMI receiver option?
- What is concept of Low-High preamplifier offered with EMI receiver?
My assumption-
- In case of EMC, one cant use pre-amplifier, as its concerned with true power returned by DUT to power line.
System block diagram
R&S result
CXA without correction factor
CXA with 10 dB correction factor
You shouldn't be concerned with dynamic range of the receivers, rather the noise floor of the receivers. I assume that you are applying the 10 dB AMN/LISN correction to the R&S receiver? The AMN/LISN has a built-in 10 dB attenuator. The signal-to-noise ratio as it applies to each of the limits. As the signal approaches the noise floor of the receiver, the influence of the noise increases. For the average limit, the noise floor must be determined using an averaging detector. For the quasi-peak limit, the noise floor is determined using a quasi-peak detector.
Since the LISN has a built-in 10 dB attenuator, you could use 0 dB attenuation in the CXA. If the CXA is similar to the MXA-N9038A, the input port on the left is intended for conducted emissions and the port on the right is used for radiated emissions. You could apply the preamplifier but must be certain that the preamplifier is not in gain compression. In most cases, a preamplifier is not necessary for conducted measurements.
Another note about the AMN/LISN. You should apply a correction for the voltage division factor, sometimes called insertion loss. This value usually varies over frequency.
You can find more information about the signal-to-noise ratio influence in CISPR 16-4-2 Annex A.