Re: [Discuss-gnuradio] USRP2 Halfband filter coefficients help

[ILKYOUNG KWOUN]

Thank you so much, Brian.

 

It saves a lot of time for me.

 

I don't have any idea for the outer and inner coefficients. But it seems that the sequence is 'Outer - Inner - 131072( = 0.5 * 2^18) - Inner - Outer. I can keep going for the analysis with this result.

It seems that the 'inner' and 'outer' coefficient things are related to the implementation of FIR filter. But I haven't seen them in my DSP books.  :-( 

Gotta google the things soon.  :-)

 

Regards,

 

ILKYOUNG

2009/11/10 Brian Padalino <address@hidden>

On Mon, Nov 9, 2009 at 11:20 AM, ILKYOUNG KWOUN <address@hidden> wrote:
> Hello folks,
>
> I need to analyze the filter characteristics of two halfband filters in
> USRP2. Since I have littel experience on Verilog HDL, I cannot pinpoint what
> exact coefficients the two halftband filters are adopting(I am reviewing
> 'gnuradio/usrp2/fpga/sdr_lib/hb_dec.v' and
> 'gnuradio/usrp2/fpga/sdr_lib/small_hb_dec.v' for hb1 and hb2.).
>
> Would somebody help me with finding out the seven and thirty one coefficents
> of filters directly?

From the comments in the header and the frequency response, these seem
to be the coefficients:

 h = [ -107 0 445 0 -1271 0 2959 0 -6107 0 11953 0 -24706 0 82359
131072 82359 0 -24706 0 11953 0 -6107 0 2959 0 -1271 0 445 0 -107 ] ;
 h_small = [ -10690 0 75809 131072 75809 0 -10690 ] ;

Does that make sense to you?  Inner and outer coefficients?  The
comments at the top of the file?

Brian