Re: [Discuss-gnuradio] CIC stop band

[Eng. Firas]

Hello,

I can give you a precise MATLAB based simulated USRP frequency response. All
what I need is the HBF coefficients. So this is an open invitation to our
dear Matt to give us his designed USRP HBF coefficients or frequency
response.

Firas,


Hans Glitsch wrote:
> 
> 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
> 
> 
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