5 Aug
2013
5 Aug
'13
10:34 p.m.
Hi Luca
Thanks for your reply.
Perhaps I am too old school. But how would one make a frequency shift of 225 KHz without
running into issues with the folded image spectrum causing a havoc?
Any more indications on asymmetric filter (complex coefficients) and then shift to
origin. is there a link to any page that addresses this in detail.
While I am being skpetic about these, I am sure everyone is doing it. How thowugh?
Regards
Date: Mon, 5 Aug 2013 17:12:38 +0200
From: luca(a)srlabs.de
To: baseband-devel(a)lists.osmocom.org
Subject: Re: Filtering in baseband spectrum
Hi Neela,
I find your question a bit off-topic in this mail list,
but still interesting for SDR geeks.
The asymmetric spectrum is quite normal when processing
complex domain signals (I/Q).
If you are only interested in a part of the spectrum, you
would normally shift it to the origin and then apply a low-pass filter.
In your case, you can apply a positive shift of 225 KHz, and then
a filter with cutoff frequency 75 KHz.
You can easily apply this transformation with GNU Radio block.
After that, you can even downsample your signal if needed.
Other methods to obtain the same result are:
- apply an asymmetric filter (complex coefficients) and then
shift to origin
- use an FFT filter, and possibly invert the spectrum in baseband
Cheers,
LM