How do I zero pad time samples if I only have frequency samples? Related to this question:
Convolution in frequency space with fft and ifft -&gt; num output samples?

When doing convolution in time domain by doing multiplication in frequency domain, you apparently can zero pad the time domain samples if you want the time domain convolution result (ifft of the fft multiplication result), to make the resulting time domain convolution be the "correct" length (len(a)+len(b)-1).

What I'm wondering is what do you do if you don't have the time domain samples yet?

I'm generating two sets of IFFT bin data, doing convolution by multiplying in the frequency domain, and then using IFFT to turn the convolution result into time domain data.

When i do this, the result is the same length as my IFFT bins though, instead of the length i would expect.

How do I lengthen the result in the frequency domain?

Thanks!
assuming I understand it, your question is interesting.  I'm "shooting from the hip" here.  I wonder if it would be useful to you to interpolate your two freq-domain sequences by a factor of two before the multiplication in the freq domain, and then performing your IFFT of the product?
[-Rick-]