explain about phase and frequency

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vinodhsaminathan

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Hi

what is phase?What is the difference between phase and frequency? how they are relate to each other? (in PLL)

Thx

- - - Updated - - -

Also explain how a PLL generate phase? can two signals have same frequency but different phase?
 
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for a sinusoidal signal:
y = A sin( 2 pi freq + phase)

where
A=the amplitude,
freq = frequency. (Gives you the number of cycles per second)
phase in a simple way tells you at what angle does the sine wave starts.
The same concept applies for any periodic signal.
Again trying to put it in simple terms:
Signals of the same frequency but different phase "start" at different times so they are displaced in time.
If they were the same phase each cycle of the two sine waves would start at the same time.

A PLL does not generate phase. It generates a periodic signal (it may be a sine wave) which phase is fixed (locked) with respect to another periodic signal taken as a reference.
 

frequency means how many time the pulse repeat itself in one second. for example a sin signal has its +ve peak and -ve peak. take its +peak and count in one second how many time it comes. It will give you frequency. and sin wave start from 0 deg. cos wave start from 90 deg. this angle tells the phase.
 

In a PLL system a phase detector responds to a phase difference between two signals: one is a multiple of the reference frequency and the other is RF VCO output. The frequencies of both are almost equal but the phase differs.
When the system is locked, it means that the frequencies are exactly equal and the locking process pulls the VCO to get a constant phase difference. A change in the phase difference in the phase detector generates an error voltage which in turn pulls the VCO frequency and phase back to the locked state.
 

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