Sorry for the confusion.
I want to find magnitude of I and Q at the same frequency and I need to
compare the two values for my purpose. Similarly, I need to find phase of
I and Q at that same ferquency and compare them. Is goertzel the fastest
way to do it?
Also, i couldnt understand what the two states of the filter are, as said
Reply by Tim Wescott●August 1, 20072007-08-01
> Sorry for the confusion.
> I want to find magnitude of I and Q at the same frequency and I need to
> compare the two values for my purpose. Similarly, I need to find phase of
> I and Q at that same ferquency and compare them. Is goertzel the fastest
> way to do it?
> Also, i couldnt understand what the two states of the filter are, as said
> by Tim.
Netiquette: Please respond within the thread. Starting a new thread
defeats the purpose of newsreaders that track things by threads.
About your question:
Maybe. You would probably be better off multiplying your I and Q
signals by sin(2*pi*f*t) and cos(2*pi*f*t) and integrating the results
over one cycle (note that you'll have _four_ answers to juggle).
I'm trying to wrap my head around the math, wondering if the relative
phase of I and Q isn't always going to be 90 degrees, but it won't go
there this morning.
Any 2nd-order filter has to carry two states. In the implementations of
Goertzel that I've seen these are the current output and the previous
tick's output. If you do a full-cycle Goertzel then the previous tick's
output will be zero and the current one will be the 'answer'. If you
don't do a full cycle you have to scale the previous output and add it
to the current one to get the 'right' answer.
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