I have a N9918A fieldfox MW analyzer which has noise figure measurement option. I want to measure noise figure of LNA but I don't know how to do exactly. Can you help to me?
Hi, at a minimum you will need a noise source. The supported noise sources are Keysight (or Agilent) 346A, 346B, 346C, or xK40/41. If you do not have one, you will need to get one.
Here is one video giving an overview of noise figure measurements with FieldFox.
FieldFox Handheld Microwave Analyzer - Measure Noise Figure Anywhere - YouTube
I made a video re: uncertainty calculations which is not quite what you are asking for. But in the video, I do show the FieldFox noise figure UI , so you get a sense of the measurements.
FieldFox Noise Figure Uncertainty Calculator - YouTube
I was going to reply RTFM to the original question, but you gave a more helpful response.
I looked at your YouTube video, and was surprised to see that you had a cable between the noise source and input of the amplifier. For the lowest uncertainty the noise source needs to screw directly onto the DUT, because the cable is going to add both mismatch and ENR uncertainties. However, I guess a 1-26 GHz amplifier is going to have a relatively high NF - I have a narrow band amplifier here which had a NF under 0.1 dB, when measured on a Keysight NF meter and Keysight noise source. Clearly one needs to be more careful when measuring very low noise figures. (I personally only have an old HP 8970A NF meter with a Noisecom 15 dB ENR noise source that has not visited a calibration lab in a few decades, so I can not make accurate NF measurements).
I know that the PNA-X VNAs can do vector error corrected measurements. I have not looked at it in detail, but I believe that it results in lower uncertainties than the Y-factor method. Is that not something that could be implemented on the FieldFox? But I guess Keysight would rather sell a PNA-X than a FieldFox.
BTW, I am 99% sure that NPL do not calibrate noise sources any more, although they used to. NPL have an open-day every 2-years, which they do really well. It is amazing that they manage to put on an event which is interesting to both school children (I think 8 or older), but also to university academics. Anyway, I phoned up before one of the open days and asked if it was possible to visit the lab where they calibrated noise sources, as I guessed they would not open up such an obscure lab to the public. Unfortunately I was told that area of NPL was closing down.
NPLs last open day was in 2018, and one was scheduled for 2020, but that was obviously cancelled. But if you (or anyone else) gets the chance to go to an open-day, it is worth phoning in advance to ask to visit a lab of interest, but which is mot open to the public. The NPL scientists are usually quite happy to talk about their work, in a way no commercial company would be able to do.
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