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
. It has a constant mag² of 
.Now, the low pass of a constant 1 is still 1.
Now, let's low pass first with a filter
and then mag². Assume filter stop band attenuation is infinite, then
because . It follows that 
. 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, address@hidden
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 address@hidden 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
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