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Simulators >> Circuit Simulators >> regarding DAC THD
https://designers-guide.org/forum/YaBB.pl?num=1181532033

Message started by venki_vlsi on Jun 10^th, 2007, 8:20pm

Title: regarding DAC THD
Post by venki_vlsi on Jun 10^th, 2007, 8:20pm

hi,
i calculated my THD by keeping a fourier component at output.
Conditions : FIn=10.1318MHz,FS=125Mhz,Cycles=83,Samples=1024.
I have plotted 512 hormonics by giving normhorm=83,hormonics=512,Fund=122.07Khz and found THD=57db.
In that 512 hormonics i taken out 5 hormonics (83,83*2,83*3,83*4,83*5)and calculated THD=63.15db.
now my doubt is whether these 512 hormonics includes THD+transient noise+thermal noise,or its only THD(hormonic components).
If it is THD+noise,is it equal to SNDR of DAC.
SNDR=S/N+THD.
Most of papers are specifying only 1st ,2nd 3rd,4th,and 5th hormonic output as THD but here we r including all frequencies till Fs/2.That the reason i got this doubt

Regards
venkats

Title: Re: regarding DAC THD
Post by ywguo on Jun 19^th, 2007, 7:13pm

Hi, Venkats,

I think that the THD reported by fourier component is SNDR (THD + SNR) actually. Since usually we don't include transient noise for input signal or sampling clock, the resultant SNR is normally quatization noise only.

To compare with other works/papers, we have to calculate THD specifying the number of harmonics.

Best regards,
Yawei