doing your computations on a reduced sampling rate always makes a lot of
sense.
Also, if you do complex to mag² prior to filtering, you get the power in
the overall nyquist band ignoring power fluctuations that do not pass
the low pass, and not the power in the pass band of the filter.
Example: Assume we have a complex sine at frequency $f>f_\text{cutoff}$
$s(t) = e^{2\pi j f t}$. It has a constant mag² of $|s|^2 = 1$.
Now, the low pass of a constant 1 is still 1.
Now, let's low pass first with a filter $h(t)$ and then mag². Assume
filter stop band attenuation is infinite, then $r(t) = h(t) * s(t) = 0$
because $f>f_\text{cutoff}$. It follows that $|r|^2 = 0 \neq 1$.
Yet another side note: have a look at the polyphase filter banks (PFBs)
that are relatively new in GNU Radio, if you want to process multiple
sub-bands at once.
Greetings,
Marcus
On 06.08.2014 16:47, [email protected] wrote:
>
>
> Try decimating after the filter, before you start computing log10 at the
> input rate. There's no need to do those calculations at the original
>
> sample rate once you've computing complex-to-mag**2 and filtered.
>
> On 2014-08-06 10:30, rejunte wrote:
>
>> Tried that, but still ocurring overflow.
>>
>> Another thing I had was that on my computer I was using a
>>
>> complex to mag^2 -> single pole IIR filter -> log10 -> multiply const (10)
>> to measure the signal strength
>>
>> that is also causing overflow on the single board computer. If I put a RMS
>> block instead, no overflow occurs.
>>
>> --
>> View this message in context:
>> http://gnuradio.4.n7.nabble.com/gnuradio-on-ubuntu-touch-tp49315p49807.html
>> [1]
>> Sent from the GnuRadio mailing list archive at Nabble.com.
>>
>> _______________________________________________
>> Discuss-gnuradio mailing list
>> [email protected]
>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio [2]
>
>
> Links:
> ------
> [1]
> http://gnuradio.4.n7.nabble.com/gnuradio-on-ubuntu-touch-tp49315p49807.html
> [2] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>
>
>
> _______________________________________________
> Discuss-gnuradio mailing list
> [email protected]
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
_______________________________________________
Discuss-gnuradio mailing list
[email protected]
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
