I have an old Samsung mobile phone that I wanted to extract the transmitter from.
I'm not sure I'd recognise it if I saw it, so I've attached a photo of the mobile phone circuitry.
Would anyone mind telling me if they think they can see the transmitter, and any other relevant details you can see from the pictures?
It isn't obvious in any of those pictures, I would guess it is on the under side of the PCBs. However, don't expect a 'module' you can remove and use elsewhere, it will be built on the PCB itself, including the antenna so it can't be used in isolation of the rest of the phone.
Other sections that you may consider to be part of the transmitter including the microphone ADC, microphone audio processing and encryption, data encoding, frequency selection and generation and the software that controls how the phone talks to cell towers are elsewhere.