How the receiver locks first on the signal?

[Gemini1706]

How the receiver locks first to the signal?

does it do symbol timing lock first, then frequency lock then phase lock?

SAy for GSM?
How about WCDMA?

How about FM?

If the receiver can lock to the freq using AFC, so what is the point of TCXO? why not just use a crystal?

Thanks in advance.

 

[RFDave]

afc vs pll

For the receiver to lock to the symbols, the symbols need to be pretty close to the right frequency. To start, the PLL needs to be at the right frequency, which translates to a specification that the crystal oscillator needs to be at the right frequency. Once the incoming signal is downconverted to the right frequency, then the demodulator can start working on symbol and timing acquisition.

In handsets, there is a feedback loop from the demodulator to the crystal oscillator to provide fine frequency control (a few PPM at most), so the need for a TCXO is reduced or eliminated.

Dave