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PAM bandwidth, QAM bandwidth

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luckyvictor

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Can someone please explain the following statement? why is twice please?

"PAM signals occupy twice the bandwidth required for the baseband."

And let say I have a PAM signal, the time waveform is at frequency 5kHz, then what is its bandwidth please?

Now the second statement is,
"When having bandwidth W for the QAM and the PAM modulaton schemes we have symobl rates 1/T, then 1/T = 2W for PAM and 1/T = W for QAM"

why is this the case?

And let say I have a QAM signal, the time waveform is at frequency 5kHz, then what is its bandwidth please?

Lastly, given the above statement we have,

"modulation efficiency R/W = 2b for PAM and R/W = b for QAM, where R is data rate and b is number of bit"

therefore according the above statement, for a given W and b, PAM is transmitting double the data rate R, why? are we not expecting QAM to transmit double since it uses two waveforms at a time.

thank you so much
 

bulx

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What is missing above is how many levels is the PAM scheme using and number of constellation pints in the QAM. Both QAM and PAM can occupy same BW depending on the pulse shape used for modulation.
-b
 

luckyvictor

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Apart from my question 3, do we need this information in order to answer my 1st and 2nd questions?
 

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