I know that up sampling by L means padding L-1 zeros between each samples. My question is how it is done practically? Do we use MATLAB or any other software, or there are hardware circuits to do so.


1 Answer 1


If padding L-1 zeros were the only thing that's done for upsampling, nobody would actually store the end result with zeros that way, because the zeros would be redundant.

In practice, padding with L-1 zeros is always followed by low pass filtering. If that filtering is done with an FIR filter, a dumb implementation would have many coefficients being multiplied by 0. A smart implementation will instead use a polyphase approach where only those coefficients that won't see a guaranteed 0 will be multiplied and summed.

So that partially answers your question: most hardware or software implementations won't even do any padding. They will instead cycle through a set of polyphase filter coefficients, and do something with the result of these successive FIR filter outputs.

Things might be different when doing Matlab or a NumPy implementation: in that case, quick prototyping is often more important than the computational or storage efficiency of the implementation, and rather than using a polyphase filter, people will indeed insert zeros in between samples and convolve the result with the non-polyphase version of the FIR filter.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.