Release 1.0
Technical Documentation 01/2006
TD_Repair_L3_SXG75_R1.0.pdf Page 12 of 73
5.3 Transmitter
5.3.1 GSM TX modulation
The GSM transmitter uses a Offset Phase Lock Loop Architecture. The high power VCO is external
to the RTR6250. A feedback signal from the VCO is down-converted and the phase compared to
that of an upconverted version of the IQ signals from the baseband. The control signal is filtered and
passed to the high power VCO.
Blockdiagram RTR6250
5.3.2 GSM dual band TX VCO
• The GSM TX VCO (Z300) is external to the RTR6250 and uses filtered signals
(GSM_TX_CP) from the RTR6250 to provide the GMSK signal to the power amplifier.
PA
Circuit diagram (sheet 3)
Company Confidential
2006©BenQ
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