I am trying to measure noise floor levels down to 10nV/rt-hz on a piece of equipment with a spectrum analyzer.
I'm looking at signals < 100kHz. I am using a 40dB low noise amplifier (LNA) , wired onto the DUT board and measure it's output with the analyzer.
This helps but, I am still getting significant broadband noise due to the GND connection between the DUT and the analyzer.
A few notes:
1. the LNA is GNDed on the DUT and is powered by 9V batteries (+-9V) to remove bench supply GND loops from the equation.
2. LNA is built using low noise op-amp, En-rti is about 3nV/rt-hz over 200Hz-100kHz
I can reduce the GND loop noise slightly by strapping the DUT to the analyzer GND with heavy braid but, not good enough.
I will next try "floating" the analyzer but, this is not usually a great idea.
Any other good ideas/techniques I could try?
I'm looking at signals < 100kHz. I am using a 40dB low noise amplifier (LNA) , wired onto the DUT board and measure it's output with the analyzer.
This helps but, I am still getting significant broadband noise due to the GND connection between the DUT and the analyzer.
A few notes:
1. the LNA is GNDed on the DUT and is powered by 9V batteries (+-9V) to remove bench supply GND loops from the equation.
2. LNA is built using low noise op-amp, En-rti is about 3nV/rt-hz over 200Hz-100kHz
I can reduce the GND loop noise slightly by strapping the DUT to the analyzer GND with heavy braid but, not good enough.
I will next try "floating" the analyzer but, this is not usually a great idea.
Any other good ideas/techniques I could try?