Filtering Problem

[darkwave]

I've a sort of digital white noise (I mean I expect that my data in of the filter is completely random) generated at a Fs= 10Mhz.
For simplicity imagine a signal whose spectrum is flat with an amplitude of 1.
Call that xn.

Imagine that I wanna filter it with a rectangular window (-6Mhz,+6MHz). Call that hn.

Cause 6MHz > 5MHz (Nyquist), I oversampled the xn of a factor 2.
So I do zero padding and filter it.
Cause my signal is digital what I expect is that when I do zero padding I change the Fs to 2Fs (20Mhz). For this reason now I can do my previous filtering.

I expect to have in out a signal yn that has a rectangular shaping spectrom centered at 0Hz and large 12Mhz (from -6Mhz to +6Mhz).
Moreover I've replication of this specter at each multiple frequency of 20Mhz.

Is all true or I miss something?

Thanks in advice

[charan langton]

If I am understanding it clearly, you have a flat noise signal. You want to filter it with a rectangular filter of 12 MHz. To do that you would need to sample the signal at at least 24 MHZ and that wont be enough. You would need to sample at a higher rate just to see the shoulders of the filtered signal. Zero padding wont help in this case.

Charan Langton