Hello everyone

So as I understand in coherent demodulation, it is necessary to obtain the carrier phase in order to demodulate the received signal (is this to generate a carrier wave with a matching phase in order to be used in the matching filter to detect the received symbol?), so if this is true, why isn't the phase of the carrier wave at the transmitter constant or known, or is it known initially but changes or is affected drastically when it is transmitted through the channel?

Or maybe there is some something that I'm completely missing? Kindly enlighten me.

Thank you

 

Hello everyone

So as I understand in coherent demodulation, it is necessary to obtain the carrier phase in order to demodulate the received signal (is this to generate a carrier wave with a matching phase in order to be used in the matching filter to detect the received symbol?), so if this is true, why isn't the phase of the carrier wave at the transmitter constant or known, or is it known initially but changes or is affected drastically when it is transmitted through the channel?

Or maybe there is some something that I'm completely missing? Kindly enlighten me.

Thank you

Wikpedia explains it far clearer than I could:
https://en.wikipedia.org/wiki/Carrier_recovery

 

Wikpedia explains it far clearer than I could:
https://en.wikipedia.org/wiki/Carrier_recovery

Lemme take a look at it