isuue in the output of my sigma delta modulator

[abdoo]

hi,

i'm trying to design a sigma delta modulator using matlab

i'm expecting a digital stream where impulse frequency changes for ex when applying a sine wave as input

but what i found is a bit stream with constant frequency

i had attached the matlab code,

the sample time is Fs * 64,

kind regards,

abdoo

 

[FvM]

SDM output is rather pulse density than pulse frequency modulated. You'll see a varying frequency only near minimum and maximum signal level.

 

[abdoo]

SDM output is rather pulse density than pulse frequency modulated. You'll see a varying frequency only near minimum and maximum signal level.

Thank you Fvm

yes i know this but even near minimum and maximum i did not see the pulse density.