Thanks, Tom. I do intend to decimate the 50MHz input by 50 to have 1MHz. Is
that correct?

Also, if I take my 50MHz source USRP, and run it through the filter with
decimation and low pass filter set to 15000000 (15MHz)
center frequency @ 15000000 (again, 15MHz)
Taps = firdes.low_pass(1, samp_rate, 15000000, 100)

Will that give me a 30MHz signal to save to a data file and run back
through the filter I initially asked about?

Thanks.

Paul B. Huter
On Nov 18, 2013 9:46 AM, "Tom Rondeau" <[email protected]> wrote:

> On Mon, Nov 18, 2013 at 10:35 AM, Paul B. Huter <[email protected]>
> wrote:
> > If I want to use a low-pass filter to look at 1MHz blocks of data, is it
> > appropriate to use the following parameters:
> >
> > low pass filter: 500khz
> > center frequency: -500khz (for 1MHz, increments of 1MHz for others)
> > Taps: firdes.low_pass(1, samp_rate, 500000, 100)
> >
> > Paul B. Huter
>
> For a low pass filter, you specify the passband bandwidth, but it's a
> real-valued filter, so it's symmetric about 0. So, yes, if you set the
> bandwidth of the filter to 500 kHz, then the filter will filter from
> -500 to +500 kHz.
>
> If you just want to look at 1 MHz of spectrum, I suggest you also
> decimate the incoming signal so that you reduce your processing
> requirements as well as filter.
>
> Tom
>
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