Marcus,
Thanks for very nice explanation:
so I see the code of this block with the help of your reply, and understand that how It is computing power for given N samples.
i.e power= (sum of X**2[n])/N where n goes from 0 to N.
And the code contains “noutput_items ” in place of N.
Then what value of N is used here. and how can we change that from python code?
~Dilip
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From: Marcus Leech
Sent: Thursday, August 29, 2013 8:44 PM
To: address@hidden
Cc: address@hidden
For a complex signal, the instantaneous power level is proportional to (I**2 + Q**2), which you then average.
This is precisely what probe_avg_mag_sqrd does.
And, you shouldn't refer to it as an "energy level", since you're measuring power, not energy. Those are different (but related) concepts in physics.
Now reducing even further, remember that the ADC is sampling a *voltage* level. The power flowing through a circuit is proportional to the square of the voltage.
The samples that are coming into the flow-graph are proportional to the voltage seen by the ADC, so in order to calculate the power, you have to square them.
Review Ohms law to see that this is true.
on Aug 29, 2013,
dilip thapa <address@hidden> wrote:
Hi,
I want to do energy detection of received signal, And after searching I was advised to use probe block to do the sense. (gr.probe_avg_mag_sqrd_f).
Can anyone explain how this works. How level() method gives the energy level. I need mathematic behind this function. Is this calculates based on FFT or what?
Please help
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