Re: [Discuss-gnuradio] gr_firdes cutoff frequency

[Martin Braun]

Hi Songsong,

the cutoff frequency is relative to the given sampling rate, whatever
that is. The firdes stuff doesn't know about the "true" sampling rate.
It's not uncommon to set the sampling rate to 1 and then have cutoff
somewhere in between 0 and 1.

MB


On Mon, Dec 12, 2011 at 02:53:07PM +0900, Songsong Gee wrote:
> I'm looking benchmark program and now found use of gr.firdes.low_pass:
> 
> 
>         chan_coeffs = gr.firdes.low_pass (1.0,                  # gain
> 
>                                           sw_decim * 
> self.samples_per_symbol(),
> # sampling rate
> 
>                                           1.0,                  # cutoff
> frequency: midpoint of trans. band
> 
>                                           0.5,                  # width of
> trans. band
> 
>                                           gr.firdes.WIN_HANN)   # filter type
> 
> 
> I checked that low pass function in doxygen, and it says cutoff frequency has
> unit measure [Hz].
> 
> Recalling above expression, it says that cutoff frequency is 1.0 Hz
> 
> Is it right? Or is it a factor that is normalized to the sampling frequency?
> 
> 
> I'm asking about it because I want to use band_pass filter and I have no idea
> what value I have to choose for low/high cutoff frequency
> 
> 
> --
> 
> Seokseong Jeon, PhD Candidate
> 
> Communication & Networks Lab
> 
> IT Convergence Engineering (ITCE), POSTECH, Korea
> 
> +82 10 8338 1229, gee.songsong at gmail . com
> 
> 

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


-- 
Karlsruhe Institute of Technology (KIT)
Communications Engineering Lab (CEL)

Dipl.-Ing. Martin Braun
Research Associate

Kaiserstraße 12
Building 05.01
76131 Karlsruhe

Phone: +49 721 608-43790
Fax: +49 721 608-46071
www.cel.kit.edu

KIT -- University of the State of Baden-Württemberg and
National Laboratory of the Helmholtz Association

pgpsVEMUdDWC7.pgp
Description: PGP signature