N4002A Datasheet, PDF (5/13 Pages) Keysight Technologies – SNS Series Noise Sources

05 | Keysight | N4000A, N4001A, N4002A SNS Series Noise Sources - Technical Overview
The Importance of Noise Source Reflection Coefficient
Two aspects of noise source reflection coefficient are important to note:
–– A non-zero reflection coefficient contributes to re-reflections between the DUT and
the source. The reflections cause uncertainty in the noise power emerging from the
source. The measured noise figure, furthermore, refers to the actual noise source
impedance rather than the desired 50 Ω value. The low reflection coefficient of Key-
sight SNS Series noise sources can keep this uncertainty under 0.1 dB.
–– The change in reflection coefficient between On and Off can cause DUT Gain vari-
ations which, in turn, can cause noise figure measurement errors. This problem is
effectively eliminated by the N4000A, whose complex reflection coefficient change
is specified to be less than 0.01.