3. TECHNICAL BRIEF
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Figure. 3.5.3 TRANSMITTER CHAIN BLOCK DIAGRAM
3. TECHNICAL BRIEF
3.5.2.2 Transmitter
The GMSK transmitter supports power class 4 for GSM850 or GSM900 as well as power class 1 for
DCS1800 or PCS1900. The digital transmitter architecture is based on a fractional-N sigma-delta
synthesizer for constant envelope GMSK modulation. This configuration allows a very low power design
without any external components.
Up- and down-ramping is performed via the ramping DAC connected to VRAMP.
3.5.2.3 RF synthesizer
The X-GOLDTM110 transceiver contains a fractional-N sigma-delta synthesizer for frequency synthesis in
RX mode. In TX mode, the fractional-N sigma-delta synthesizer is used as a Sigma-delta modulation loop
to process the phase/frequency signal. The 26 MHz reference signal is provided by the reference oscillator.
This reference signal frequency serves as the comparison frequency for the phase detector and provides
the digital circuitry with a clock signal.