luoshuer
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Posts: 5
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Hi Guys
I am new to signal to noise ratio and may have really stupid question, which confused me a lot. I am try to interpret attached DAC output spectrum.
(a) If I want to calculate the rms noise voltage from DC to 40MHz, I can do square-root( integral ( noise power from DC to 40MHz)), the noise floor is around -40dB.
so VnoiseRMS= squareroot( ( 1e-4)^2 * 40e6) = sqaureroot(4e-1)=0.632Vrms. It it correct, I feel this is too HIGH, as it is close the the fundamental signal???
(b) If I look at the fundamental signal, this is 25MHz,-3dB at the peak. Do I immediately get Vsignalrms=0.5Vrms as 10log(0.5)=-3dB?
Or I have to integrate the signal power from 24MHz to 26MHz, then take squareroot to get Vsignalrms?
Many thanks, shuer
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