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This is more of a doubt rather than question. Just correct me if I am wrong, tks

So i have this question, (not exactly maths but my doubt is related to calculation understanding)

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The question here is the phase shift column when they say 1/(4f) are they saying (1/4)*360? which ofcourse mean 90 degrees.. I deduce this cause it is a sine wave am I right? that is my question and doubt.

JackyBoi
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1 Answers1

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f here means frequency, or rather 2pif is frequency according to the bottom of the table. So, f=440 for concert A, which is 440 Hz=cycles per second, or 2pi*440 times the frequency of a normal sine wave (which has period 2pi, not 1).

EDIT: I don't know QAM exactly, but I know what's going on with the waves. I think the frequency is fixed in the original signal. So the phase shifts are just fractions of the original frequency. Look at the points $(\frac{n\pi}{4}, sin(\frac{n\pi}{2}))$ on a sine wave (see Wolfram Alpha), then try and change the frequency of the sine wave and see what happens. If you double the frequency, the phase shifts should also be multiplied $sin(2\pi t+\pi /2) \rightarrow sin(2 \pi ft+\pi f/2)$. So if you always shift by $\frac{n}{4f},$ your phase shift will be the absolute time shift of $\frac{n}{4}$, no matter the original frequency. Look up radians to degrees conversions.

If that's what you're expecting, good. Otherwise there's some missing information.

Loki Clock
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  • are you familiar with QAM? cause now your answer is even more confusing, updated with the full question, i just want to know if it is 90 degrees or 180 or 270 pls chk..tks – JackyBoi Mar 03 '13 at 11:23
  • No, but I'll try to decipher. By period 1, I think they mean after 1 second, since they adjusted the units to Hz. – Loki Clock Mar 03 '13 at 11:25
  • So, yeah, they mean a quarter of a second shift. The waves all seem to have a frequency of 1 Hz, so the shifts are (0, 1/4, 3/4, 0, 1/2, 1/2, 3/4, 1/2). – Loki Clock Mar 03 '13 at 11:44
  • yes that is what I tot as well... tks – JackyBoi Mar 03 '13 at 12:11