im hearing about the phase, but i dont know what i can do with phase ?
i know my question is not specific but im looking for general talking.
thaaanks

 

The phase of what?

Phase-Modulation or general phase shift or phase displacement


Phase modulation (like amplitude mod and Freq mod) is a method for encoding infomation over the airwaves, it is best suited to digital trasmission

Phase shifts occur with all filters or anything that inflicts a delay

phase dsiplacement like on the national grid is describing the orientation of the three phase power being trasmitted. Power is transmitted at 50Hz, but in the 3phase system the 3 SIN waves are trasmitted at 120deg displacement from each other

so what specifically are you interested in?

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hi Mr.Styx
im looking for phase(shift&displacement)
thanks for your reply

 

Every system has a magnitude response and a phase response. To change phase, you will have to design a system with your desired phase response. Filters that change only phase, but maintains magnitude are known as all-pass filters, or phase shifters.

Once you can control phase, you could encode a signal's information in it's phase, then known as PSK modulation. Or tweaking a system's phase response can give you better performance, as in lead/lag compensators.

Sometimes, when a signal passes from point A to B through an unknown system, and hence an unknown phase response, it is desired to maintain a common reference phase. This is known as synchronization and it's where all your PLLs come in.

I guess at this point of time, all you need to be clear of is the meaning of phase. All it's implications and applications will present themselves as you delve into the other topics.

 

[quote="Styx"]The phase of what?


Phase modulation (like amplitude mod and Freq mod) is a method for encoding infomation over the airwaves, it is best suited to digital trasmission

/quote]

Phase modulation is not a digital scheme. The only difference between FM and PM is that FM has an integration in the phase portion of the complex envelope function.

 

IF you are going to quote me at least quote me correctly and understand what I wrote and what you quoted!!!! it only shows your ignorance

I say
you say
When did I say that PM was a digital scheme!!! I said it was best suited to digital transmission!!!!!

You can send analogue infomation via AM,FM and PM
Equally you can send digital via AM,FM and PM.

However, PM is actually used primarily in mobile phones. Yes the decoding is alot more complex. However, GSM mostly operates in either the 900Mhz or 1800Mhz band. The digital processing uses phase modulation that results in only a very small and essentially random changes in the amplitude of the carrier wave.

Please do not miss-quote

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I think you need a review of your communications. Perhaps you're thinking of PSK.

 

Actually I think you do

Phase shift keying is still phase-modulation

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All right I'll concede that. However I interpreted PM as not PSK, but as what is actually called Phase Modulation. The complex envelope function is

g(t) = A*exp(j*m(t)). For FM it is g(t) = A*exp(j*integral(m(t))). However what you actually transmit is Re{g(t)}.

Because what you're referring to is called PSK or phase shift keying I suppose it is "phase modulation" as you're modulating the digital data in phase part of your message, however its not called PM. You need to be more careful about how you write.

 

Sometimes, I too make the mistake of forgetting that all are here to learn and share. But it seems that these forums just got less friendly over time.

 

Agreed. I'm sorry I came off harsh.

 

To answer the original question; phase is about time. The time difference between two waveforms of the same frequency can be measured in degrees of phase. One complete cycle of a sine wave is 360 degrees. If two waves differ by 1/4 cycle, that is 90 degrees and is a different time for different frequencies. In a capacitor, the current phase leads the applied voltage and in an inductor, the current phase lags the applied voltage.

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Hey everyone i read your information about phase .
But i want to ask for Three Phase systems in balanced and unbalanced loads
Please help me