On 11/28/2010 06:53 PM, Vladutzzz wrote:
Marcus,
First of all thank you for your reply!
I have some questions about your very much appreciated explanations:
After using the complex-to-mag-squared block, should I consider the
coefficients as being in W or mW (should I use 10*log10 or 30 + 10*log10 to
get the power value in dBm)?
What is the function of the single-pole-iir_filter? What does it actualy do?
I'm asking this so I will know how to calculate its parameters. Does it give
the frequency bin based signal band, a more rounded appearance?
Again thank you for your help!
I hope other people will also find this useful.
Vlad.
You expressed a desire to measure power over a finite bandwidth (at
least, that's what I think
you were asking).
The values after the complex-to-mag-squared block are *unscaled* total
power estimates over
the input bandwidth. The IIR filter is used to smooth the result--in
a hardware power detector,
it would be a simple R-C network, here we use a simple single-pole
IIR filter, although you could
use a simple FIR low-pass as well, but the single-pole IIR is cheap,
and has adequate
behaviour for total-power detection--it's what I use in radiometry.
In order to convert to your favourite units (like dBm), you'll have to
take some
*experimental measurements*, and scale the output values
accordingly. Please re-read
my original reply, I'm not going to repeat it here.
--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
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