1. Field of the Invention
The present invention relates to an architecture, for a transmitter in a mobile communications system and particularly, but not exclusively, to an architecture for a base-station transmitter which supports frequency-hopping in a TDMA environment.
2. Description of the Related Art
At present in Europe a GSM standard operates for transmission of information in the mobile communication network. According to that standard, information is transmitted in a sequence of time slots, each time slot having the possibility of being allocated a different carrier frequency for modulating the information to be transmitted. The GSM standard requires that transmitters in base station transceivers can switch their frequency (frequency-hop) between consecutive time slots. This has been achieved according to a known transmitter architecture by providing a so-called “ping-pong” synthesizer which generates different frequencies on a time slot basis. While this technique works, it requires high isolation between the synthesizers which is difficult to achieve.