Spectral analysis box query about amplitude and power
Posted: Wed Feb 15, 2012 1:29 pm
I am designing for EEG analysis and want to use the Spectral Analysis box. I see it has amplitude output, as well as phase, real and imaginary outputs. I want to make use of the power in the spectrum, which is amplitude squared. But I am confused by the terminology used in the Spectral Analysis box and associated boxes. Using information from the tutorials/examples for these boxes...
Spectral Analysis box says:
possible outputs include the spectrum amplitude (the power of the signal in a number of frequency bands).
Power Spectrum Display says:
We connect the 'Amplitude' output connector of the Spectral Analysis box to the input connector of a Power Spectrum Display box. The player may now be launched to visualize the power spectrum of the signal.
One question is... if the Spectral Analysis box outputs spectrum amplitude... then does the Power Spectrum Display box square the spectrum (amplitude) input before display?
I want to use the Frequency Band Selector box... it says its input is 'Input Spectrum'... is this the spectrum amplitude from the Spectral Analysis box?
I also want to use the Spectrum Average box... its input just says 'Spectrum'... does this take the spectrum amplitudes and average them?
As I said at the beginning, I want to use the power in the spectrum, but am not sure when to square the spectrum amplitudes... my guess is that I use a Spectral Analysis box, followed by a Frequency Band Selector box, followed by a Spectrum Average box, which should give me the average of spectral amplitudes over my chosen band of frequencies, and then square this averaged amplitude to provide the spectral power indicator I need.
Sorry for the lengthy discussion, just trying to make as clear as possible what is it I need to know about the boxes associated with spectral analysis so that my design theory will be correct.
Any help appreciated
Thanks
Robert
Spectral Analysis box says:
possible outputs include the spectrum amplitude (the power of the signal in a number of frequency bands).
Power Spectrum Display says:
We connect the 'Amplitude' output connector of the Spectral Analysis box to the input connector of a Power Spectrum Display box. The player may now be launched to visualize the power spectrum of the signal.
One question is... if the Spectral Analysis box outputs spectrum amplitude... then does the Power Spectrum Display box square the spectrum (amplitude) input before display?
I want to use the Frequency Band Selector box... it says its input is 'Input Spectrum'... is this the spectrum amplitude from the Spectral Analysis box?
I also want to use the Spectrum Average box... its input just says 'Spectrum'... does this take the spectrum amplitudes and average them?
As I said at the beginning, I want to use the power in the spectrum, but am not sure when to square the spectrum amplitudes... my guess is that I use a Spectral Analysis box, followed by a Frequency Band Selector box, followed by a Spectrum Average box, which should give me the average of spectral amplitudes over my chosen band of frequencies, and then square this averaged amplitude to provide the spectral power indicator I need.
Sorry for the lengthy discussion, just trying to make as clear as possible what is it I need to know about the boxes associated with spectral analysis so that my design theory will be correct.
Any help appreciated
Thanks
Robert