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.
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.
Circuit diagram (sheet 3)
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