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Design >> Mixed-Signal Design >> interpolation
https://designers-guide.org/forum/YaBB.pl?num=1386758031

Message started by aman gupta on Dec 11^th, 2013, 2:33am

Title: interpolation
Post by aman gupta on Dec 11^th, 2013, 2:33am

Can anyone explain me what is the effect on frequency spectrum due to zero padding in a discrete time signal for interpolation ??
here i am attaching a pic from "cmos mixed signal circuit design by baker". here in the second fig even due after zero padding only the sampling frequency is shifted but rest of the spectrum is same. How is it possible ?

Title: Re: interpolation
Post by boe on Dec 11^th, 2013, 4:16am

Aman gupta,
To understand this, you should look at the process in the (continuous) time domain: nothing happens. So the spectrum remains the same - only the sampling frequency changes, as indicated in the picture.
- B O E

Title: Re: interpolation
Post by aman gupta on Dec 11^th, 2013, 5:51am

got it.... thanks.... but 1 more doubt... if after sampling, there is no aliasing i.e my sampling rate is greater than the nyquist rate, then how interpolation will be useful ???

Title: Re: interpolation
Post by boe on Dec 11^th, 2013, 9:59am

Aman gupta,
in case you want to change the sampling rate...
- B O E

Title: Re: interpolation
Post by aman gupta on Dec 11^th, 2013, 10:26pm

but what is the advantage of changing the sampling rate ?
is their any benefit on the reconstruction filter design with up-sampling ?

Title: Re: interpolation
Post by boe on Dec 12^th, 2013, 2:19am

Aman gupta,
Quote:

is their any benefit on the reconstruction filter design with up-sampling ?

yes, there is. See figure.
- B O E

Title: Re: interpolation
Post by aman gupta on Dec 12^th, 2013, 8:21am

but even after up-sampling, we have to remove image components. If we can't remove out of band components in the originally sampled signal completely then how can we remove image components in the up-sampled signal ?

Title: Re: interpolation
Post by boe on Dec 13^th, 2013, 10:14am

Aman Gupta,
it is much easier to do so in the digital domain than in the analog domain.
Upsampling is also useful for displaying waveforms if the signal frequency is close to the Nyquist limit.
- B O E