Noise Figure Y factor method calculator


This calculator implements the method of Agilent application notes AN 57-1 and AN 57-2 for noise figure measurement, with the addition of an adjustable attenuator after the noise source and between the DUT and instrument. This web page is not a tutorial on noise figure measurement, the above two applications notes do such a good job that I wouldn't try to improve on them. The terminology on this page is largely consistent with that in the applications notes.

Fig 1: Noise Figure measurement using a two stage system.

The terms used in the calculator are as per Fig 1. 

Data entry

Noise measurements may be entered depending on your selection of "Noise Off/On" units on the input form, (consistently) in:

  • dBs;
  • watts (or proportional to Watts by a constant, eg all input in mW); or
  • volts  (or proportional to Volts by a constant, eg all input in mV)

Enter only a number in decimal format, no units.

The calculator permits a different noise source for the two stages, this might be required where the DUT is a frequency converter. The calculator will stop processing if it detects conditions that would not occur in practice (eg negative Te).

Where only an overall system NF is desired (the NF12 above), a one stage test is adequate. Where the NF of a component (NF1 above), then a two stage test is needed to derive the DUT NF1 and GAIN G1.

ENR is defined wrt 290K, and is not defined for Th<=290K, and will be shown as ***.

Input form

Noise Off/On units Stages  
Stage 2:
Noise source:  Cold temperature (K)
Att12 (dB)   Temperature (K)  Att22 (dB)   Temperature (K) 
Noise Off  Noise On 
Stage 1:
Noise source:  Cold temperature (K)
 Att112 (dB)  Temperature (K)  Att212 (dB)  Temperature (K) 
Noise Off  Noise On 



If you're clever, you will have worked out you can download this page to your hard disk. If you're smart, you won't, you will run it from the web site and automatically take advantage of any updates.

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© Copyright: Owen Duffy 1995, 2021. All rights reserved. Disclaimer.