The spectrum analzyer's attenuator causes an internal increase in gain at the IF stage after the mixer and amplifies the device's noise floor (regardless of the input). Enough attenuation will attenuate your noise down to -174dBm/Hz (at 290K). However, the reason for the increased noise floor isn't the attenuator. To sum it up: So, using my current setup, with a 30dB external attenuator and a 10dB 'Attenuation' setting in the oscilloscope, if I read a power level of 'x' at a frequency of interest, what is the actual absolute power which is being measured? Is it x+20dB? Or x+40dB?Īlso, can you please explain what the attenuation setting in a Spectrum Analyzer does?įeynman gave a great answer (reference level for external attenuation and the noise floor increasing by adding attenuation). So, my question is, have I done a mistake by using the 10dB attenuation setting when I was actually using a 30dB attenuator externally? Or does the attenuation setting mean that an additional 10dB of attenuation is provided inside the spectrum analyzer? When I made the measurement, the 'Attenuation' setting was on 10dB. When I obtained the RF power spectrum, I noticed that there was a setting in the Spectrum analyzer called 'Attenuation', which I could change by using the various knobs provided in the control. So, I am using a 30dB attenuator before the Spectrum Analyzer input in order to ensure that the power levels entering the instrument is well within the design limits of the device. I am a beginner in this topic, so I apologize if the question is too silly. I have to make measurements of the RF power which a circuit is delivering, and I am using an RF spectrum analyzer for that purpose.
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