LG -A100 Service Manual page 34

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.
Figure. 3.5.3 TRANSMITTER CHAIN BLOCK DIAGRAM
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.
LGE Internal Use Only - 34 - Copyright © 011 LG Electronics. Inc. All right reserved.
Only for training and service purposes