Re: [Discuss-gnuradio] CIC stop band

[Hans Glitsch]

Hello,

 

Thank you for the graphs.  I wasn't aware that there was a HBF after the CIC.  Yes, I'd like to know the frequency response of the whole usrp from input to output when I decimate by 250.

 

Thank you to everyone for the help so far,

Hans

----- Original Message -----

From: Firas abbas

To: Hans Glitsch

Cc: gnuradio mailing list ; Eric Blossom

Sent: Wednesday, May 16, 2007 11:19 PM

Subject: Re: [Discuss-gnuradio] CIC stop band

Dear Hans,

I think you meant the frequency response of CIC+ HBF  filters. However, the USRP CIC decimation filter has 4 stages. I did MATLAB analysis for 4 stages CIC filter with decimation rate of 250 (as you requested) without the HBF. The spectrum analysis result is attached. The first plot is for entire range [0 to Fs/2]. The second one is zoomed near the interested band. You will see a huge theoretical gain (more than 190 dB) because of CIC bit growth.

Firas

Eric Blossom <address@hidden> wrote:

On Wed, May 16, 2007 at 04:00:24PM -0700, Hans Glitsch wrote:
> Hello,
>
> What is the stop band of the FPGA CIC filter? How do I figure out the
> attenuation at a given frequency outside my bandwidth?
>
> I'm decimating by 250.
>
> Thanks,
> Hans

It's a fourth order CIC.
See http://users.snip.net/~donadio/cic.pdf for the transfer function.

Eric


_______________________________________________
Discuss-gnuradio mailing list
address@hidden
http://lists.gnu.org/mailman/listinfo/discuss-gnuradio

---

---

---

Internal Virus Database is out-of-date.
Checked by AVG Free Edition.
Version: 7.5.467 / Virus Database: 269.6.5/792 - Release Date: 5/6/2007 9:01 PM

--
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.