We would like to measure a LNA with frequency range 25GHz to 28GHz and would like to use Downconverter Mode on our N8973A noise figure analyzer.
Could you recommend a Downconverter for this application? Does Keysight sell this Downconverter for this application? Does Block downconverters that are used with N8975A will work with N8973A?
Thank you very much for your support.
Best regards,
Timothy
You have a difficult question to answer. The N8973A cannot be used with the block downconverters. The block converters are fixed LO, variable IF. The fixed LO frequency of the K40 is 18 GHz. This means that for the frequencies you are looking at, the IF will be 16.5-18 GHz. (18 GHz at 26.5 and 16.5 GHz at 28 GHz.) The N8975A or the new N8975B with a converter is a better choice, but you may have trouble getting the block converters without the NFA. The new N8976B (you would need to check this out at Keysight.com) could also work. Should you use the N8975, you would need the K40 for your frequency range. For frequencies below 26.5 GHz, you would be using the N8975A/B direct. Each band would need to be characterized.
Another alternative is to use a spectrum analyzer with noise measurement capabilities and use an external mixer/converter above 26.5 GHz such as the 11970 series. This would be using the LO output of the SA to drive the mixer. Loss through such a mixer is high, so you would need a low noise amplifier as well. Uncertainty in measurement will be higher as well. You could also use the block downconverter with the SA as well, if you can locate one. Another option, a network analyzer with noise figure application.
Here is a link to an Uncertainty Calculator to help guide you. https://www.keysight.com/find/nfuc
All of the options are expensive. It's also possible to rent the equipment you need. Rental companies are set up to help determine which instruments you would need.
Hope this helps you,
noiseguy