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How to measure VNA Noise Floor?

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Wingmaker101

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Hello, every VNA sold has noise floor specifications in their datasheet. Noise floor level is used to calculate its dynamic range.

So anyone know the right method to measure VNA noise floor?
 

Thanks, the paper documents how noise floor is defined, and ways to reduce noise floor level thus improving dynamic range.

Does anyone know exactly how to measure it on VNA screen? For example, do we measure S11 when measuring noise floor of VNA Port 1? Do we turn off the RF power, etc?
 

A quick check would be to calibrate the VNA, and after this, put the 50 ohms load from the cal-kit on port 1, and do a scalar S11 measurement.
The S11 indication is the noise floor of the VNA for a specific frequency. The test includes the measurement bandwidth.
As the document posted above mention, the noise floor of the VNA can be reduced by increasing averaging and BW reduction.
 

if it were me, i would get something like a 70 dB step attenuator, leave the IF bandwidth high, and start clicking in 10 dB steps. when the measured S21 magnitude departs significantly from the step attenuator reading, i would say i hit the noise floor.
 

A quick check would be to calibrate the VNA, and after this, put the 50 ohms load from the cal-kit on port 1, and do a scalar S11 measurement.
The S11 indication is the noise floor of the VNA for a specific frequency. The test includes the measurement bandwidth.
As the document posted above mention, the noise floor of the VNA can be reduced by increasing averaging and BW reduction.
If we measure S11, it is in dB, a ratio measurement. How do we quantify the noise floor level in dBm though?
 

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