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ACP Measurements: Noise Reduction (NCORR vs NFE)

Question asked by pxaphil on Feb 18, 2010
Choosing the best noise reduction method:  User Noise Correction vs. Noise Floor Extension

Question:  For Adjacent Channel Power Ratio (ACP) measurements, when should I use User Noise Correction (NCORR) vs. using Noise Floor Extension (NFE) to achieve noise reduction and improve my effective dynamic range?

Answer: The NCORR (Noise Correction) feature of the Agilent X-series analyzers allows the user to characterize the noise floor of the analyzer, correct for it and thus benefit from improved dynamic range when making ACP measurements. However, this can be time-consuming because the characterization of the analyzer noise floor must be repeated for each change in the analyzer’s state (such as frequency, Resolution BW or attenuator setting). The NFE (Noise Floor Extension) feature of the PXA signal analyzer also allows the user to correct for the noise floor of the analyzer and provide improved dynamic range. However, NFE uses a stored factory calibration of the analyzer’s noise floor that applies over the full range of operating conditions and settings. The resulting corrections are performed dynamically during measurements. Hence, the analyzer noise floor does not have to be characterized for each change in state, potentially saving the total time required for making a calibrated measurement.

Using Noise Correction will provide least measurement uncertainty, because the user is characterizing the instrument’s noise at the correct combination of time, temperature, frequency, and other operating conditions vs. NFE where noise was characterized at the time when the unit was calibrated at the factory and at room temperature.  In general, using noise corrections also gives about slightly more dynamic range than NFE. So choosing NFE vs. noise correction is a trade-off of measurement uncertainty vs. measurement time.