578 Keysight N9927-90001 User’s Guide
Noise Figure Mode (Option 356 – CPU2 Only)
How to Define a Noise Figure Measurement
Specified Style (Spec Style): Following the GUM method for Type B
evaluation of standard uncertainty described in Reference[1]
1
, the
uncertainty calculation takes into account not only the entered value of the
reflection coefficient, but also the nature of this value. This can either be a
measured value for the DUT, or some form of specified value. This is
indicated by the Spec Style setting. Specified Styles may be either a
percentile value, maximum, fixed, median or mean. This value indicates the
nature of the entered value relative to the population of values it represents.
Refer to Table 29-1 on page 578.
Distribution: Distribution settings refer to the population distribution of the
|
Γ| values for the device. Refer to Table 29-2 on page 578.
1. Reference [1]: GUM 1995 with minor corrections Evaluation of measurement data -
Guide to the expression of uncertainty in measurement JCGM 100:2008 First Edition
September 2008.
Table 29-1 Specify Style — of the entered value relative to the represented population
Style Description
Maximum
Use this if this value represents the largest possible reflection coefficient for the population of
devices to which the DUT belongs. This is true for "does not exceed" specifications.
Fixed
Use this if the value is a measured value for the DUT.
Median / Mean
Use this if this value represents the median / mean reflection coefficient for the population of
devices to which the DUT belongs.
95th %ile
Use this if 95% of the population has a lower reflection coefficient than the value entered. This is
the case for "2 standard deviation" (2
σ) type specifications.
80th %ile
Use this if 80% of the population has a lower reflection coefficient than the value entered.
Table 29-2 Distribution — of the population of the reflection coefficients
Distribution Description
Fixed
The reflection coefficient magnitude is always at the given level. This is often the case when
measured values are used.
Rayleigh
The probability density function (pdf) of the magnitude of the reflection coefficient is a Rayleigh
distribution. This is normally the case for specified values when the overall mismatch is due to
several interacting impedance transitions within the device.
Uniform (within a
Circle)
A distribution that was historically used in the industry, before the Rayleigh research, as
documented in Keysight Application Note 1449-3, but is rarely accurate. Refer to
https://literature.cdn.keysight.com/litweb/pdf/5988-9215EN.pdf.
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