sigma delta for audio applications - calculating SNDR

[arunkumar446]

sndr sigma.delta

in sigma delta for audio applicaitons which input frequency should be taken for calculating SNDR. audio range 20 to 22KHz or so taking a Band Width of 25KHz which frequency to take.

Thanks in advance.

 

[kuohsi]

sigma delta sndr

Fin=Fs / 2^n to fit the input frequency in 20~~22K Hz.
EX: Fs=2MHz, Fin=2M / 2^9 = 3.90625KHz
you can find Fin=3.90625KHz ,Harmonic3 = 11.71875 KHz
so you can calculate SNDR

 

[arunkumar446]

Re: sigma delta SNDR

Thanks for the reply kuohsi, if you don't mind can you be more clear with a little explanation.

what is that n and how to decide it.

is it the no. of bits we are expecting.

 

[kuohsi]

Re: sigma delta SNDR

Thanks for the reply kuohsi, if you don't mind can you be more clear with a little explanation.

what is that n and how to decide it.

is it the no. of bits we are expecting.

No, n is a arbitrary number.
use FFT function to calculate SNDR,
you can think a easy scale between fs and fin,
fs........32768
---=------------
fin........2^n
(if you want 32768 points)
so fin=fs*2^n/32768
if I do this ,I will choise n=multiple of 2, to fit fin below 22kHz

 

[al_valaee]

Re: sigma delta SNDR

It's better to calculate SNDR at these frequencies:
Fin=31*Fs/64, 15*Fs/64, ..., (2^n)-1/64.
Denominator should be power of 2.

 

[arunkumar446]

Re: sigma delta SNDR

hi al_valaee, thanks for your information, but is there any reason why to take those particular frequencies. it will be nice if i can know the reason.