# "Slicing" a complex signal

I will try to explain this the best I can… but here is what I am
looking
to do:

I have a digital signal that takes up 100kz of bandwidth. I want to
“split”
this signal and push both halves apart. The best way to explain this is,
say you have an AM signal. Normally, the LSB and USB are right on top of
the carrier in the “centre”. I want to offset the LSB and USB “apart”
from
each-other, and then have the receiver place them back in their proper
place.

I attempted to simply use the Signal Source and try to bandpass them,
but
that did not work like I wanted it to. All the other filter seem to work
on
both sidebands, and this won’t work either.

Any help here would be awesome.

Hi Jordan,

you can use (complex) bandpasses to select either halfband, and
frequency translate the results to your heart’s desire individually, if
this is what you’re after. You might need to design that filter yourself
– which isn’t as hard as it sounds:
use the gr_filter_design tool, which comes with GNU Radio, design a
lowpass with a passband of $\frac{b_\text{halfband}}2$ and shift the
taps in frequency domain by multiplying them with a complex sine
$e^{j\frac{b_\text{halfband}}{2}\pi n}$.
Also, taking the signal (twice), shifting it by $\pm\Delta_f , |\Delta_f|\geq b_\text{halfband}$ respectively, and then high passing
everything below $\Delta_f - \frac{b_\text{halfband}}{2}$ away should
work, too.
also, if possible within your nyquist bandwidth without introducing
aliases in places you need, multiplying with a real cosine (and high
passing) would do your job, too.

Greetings,
Marcus

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