Specifications

19
Appendix E:
Glossary and definitions
1. Excess Noise Ratio (ENR):
ENR is the measure of how much more noise power is
output from a noise source when “ON” (i.e. operating at
virtual temperature T
hot
) than is output when “OFF” (i.e.
operating at ambient temperature T
cold
), normalized by its
output power at the standard temperature 290K.
ENR = 10 log (T
h
- T
c
) / T
0
For example, an ENR of 15 dB means that the noise source
output when ON is greater than when OFF by the antilog
of 15/10 times the noise power ouput at 290K. This is
equivalent to a resistor at 9171K, calculated as antilog
(15/10) x 290.
2. Second Stage Contribution:
During the measurement process the noise source is
connected to the input of the DUT and the DUT’s output is
connected to the measurement system. In this cascade, the
DUT is the first stage and the measurement system is the
second stage. The measurement system will measure the
noise figure of the cascade. Correction requires that the
noise figure (F1) value of the DUT has to be de-embedded”
from the cascade’s combined noise figure (F12) by
removing the contribution of the second stage in the
cascade or Friis equation:
F12 = F1 + [(F2 - 1) / G1]
The expression in the brackets is the second stage
contribution. G1 is the gain of the DUT.
3. Y-Factor:
This is the linear ratio of the noise power seen by the
measurement system when the noise source is turned ON,
to that when the noise source is turned OFF. This is the
basis of the calculation of noise figure. After the
instrument recognizes the ENR, the noise figure is derived
from the equation:
NF = ENR - 10 log (Y - 1)
Appendix D:
Abbreviations
AGC Automatic Gain Control
DUT Device Under Test
DSB Double Sideband
ENR Excess Noise Ratio
F Noise Factor (linear expression of NF)
LSB Lower Sideband
NF Noise Figure (noise factor [F] expressed in dB)
RSS Root Sum of Squares
SSB Single Sideband
T
c
Cold Temperature
T
cold
Cold Temperature
T
h
Hot Temperature
T
hot
Hot Temperature
USB Upper Sideband
URL Universal Reference Locator
WG Waveguide