Are the inserted samples in multirate sampling always zero?

[htetphoe]

Multirate

In Multirate sampling of slow to fast ,
how are the samples between original rating sample datas inserted ?
Are the inserted samples always zero?
Is there any limitation in multirate sampling to get original information?

 

[fangf]

Re: Multirate

First insert zeros, then using lowpass filter to remove alias which making time domain samples smoothing.

 

[mark_yeh]

Re: Multirate

Generally. zeros are inserted between the original samples, but not always.

 

[jaac]

Re: Multirate

Zerro stuffing is realy named "upsampling", which creates the mirror images in the frequency domain. Lowpass filtering is what makes the reall interpolation, and removes the spectral images.

JaaC

 

[laocai]

Re: Multirate

the hardware efficiency is high if zeros is inserted

 

[jaac]

Re: Multirate

Let's discuss about it. The algorithm consists in increasing the sample rate by inserting zeros, which is called "upsampling", followed by low pass filtering, which is the real interpolation operation.

What you call hardware efficiency comes from something called Noble identities. With that mathematical trick, you can do the filtering first, then the upsampling, and sum up the samples in a time interleaved manner, so the filtering is done at the lowes possible sample rate, thus achieving high computational efficiency.

For documentation, I highly recommend you the book "Multirate Systems and Filter Banks" by P.P. Vaydianathan, a real bible on the topic.

Regards,

JaaC

 

[Sahem]

Re: Multirate

Look in RG Lions "Understanding DSP" Chapter 7.3. Digital Resampling.

 

[mark_yeh]

Re: Multirate

you can read the elementary notes about multirate.