Re: [Discuss-gnuradio] Combining filters

[Brian Padalino]

On Sat, Aug 14, 2010 at 7:59 PM, Marcus D. Leech <address@hidden> wrote:
> I have an application that's running on some fairly "spartan" hardware,
> so I'm trying to find ways to make the
>  flow-graph more computationally efficient, so that I have more
> headroom for inevitable feature creep.
>
> Part of my flow-graph has a FIR bandpass filter, which is followed
> immediately by an FFT filter.  The FIR bandpass is simply
>  to define my passband of interest (I bring in 1MHz, but only need/want
> 700KHz in the middle), and the FFT filter is designed
>  to allow me to dynamically notch-out narrowband interferers.   Is
> there an efficient way to combine these two into a single
>  filter, that will be more computationally efficient than two filters
> in series?

You should be able to convolve the time domain taps of both filters to
achieve the cascaded performance of the two filters in series.

I am not sure this would really yield any better computational
results, but it's the easiest thing that comes to mind.  Switching to
fixed point for your filtering may be the best bang-for-your-buck as
long as you don't need a massive amount of dynamic range.

I'd be interested to hear what solution you come up with.

> --
> Marcus Leech
> Principal Investigator
> Shirleys Bay Radio Astronomy Consortium
> http://www.sbrac.org

Good luck.

Brian