THD and SINAD Correlative Math Equation?

[DonH56]

Just turning off the signal works fine for analog components but is not always representative of the noise floor with signal present when measuring ADCs, DACs, and other devices that employ sampling/filtering/non-linear activity.

 

[Bob8701]

Boonton electronic in nj

 

[JohnPM]

Using 8k, 128k, and 1M for the FFT length and an RTA window:

No change in "level" a little more detail.

An RTA has bins that are an octave fraction wide. RTA bins are wider than FFT bins except at low frequencies when using short FFTs and small RTA octave fractions, so the narrower bins of the longer FFT are being summed up again into the bins of the RTA.

 

[Music1969]

So basically SINAD is 1/(THD+N) in dB scale.

Hi, if THD+N = 0.001%, then SINAD = 1 / 0.001 = 1000 dB?

 

[JohnYang1997]

Hi, if THD+N = 0.001%, then SINAD = 1 / 0.001 = 1000 dB?

0.001% = 0.00001
1/0.00001 = 100000
100000 times in dB scale is 20dB *5 = 100dB

 

[pma]

So "distortion attenuation" is sinad?

THD+N is noise and distortion and SINAD is signal to noise and distortion ratio. So it is the same thing, expressed in dB or %.