WCDMA power control
WCDMA Tx power control is accomplished by the two VGA amplifier stages in the Tx ASIC.
The VGAs have a common temperature compensation circuit and one voltage mode analogue input for gain
control (TXC).
Another function of the detector voltage is to steer the DC/DC converter, which is providing a variable supply
voltage for the WCDMA PA.
WCDMA PA module
The WCDMA PA is housed in a separate module having:
• a variable supply voltage input for the amplifier stages (Vcc11),
• a battery supply voltage for the bias circuits (Vcc12),
• and two bias current inputs.
Bias currents are generated by 5-bit DA converters in the RF ASIC.
If a different manufacturer's PA is changed to the phone, this setting must be set again.
PA DC/DC converter
The control of the DC/DC converter is fed back from the power detector circuit.
GSM transmitter functionality
An RF ASIC receives an analogue IQ modulated signal from digital BB, which is first low pass filtered with
filter corner frequency set to approximately 200 kHz. After the filter, the signal is routed to the GSM modulator.
The amplifier gives 40 dB of power control dynamic range.
After the VGA stage the signal exits the RF ASIC. In case of GSM1800/1900 the signal goes via a balun to the
GSM PA module. In case of GSM900, the PA module is preceded by a SAW filter. After the filter, the signal is
fed to the GSM front end module (FEM). Finally, the signal is routed via FEM to the antenna.
Figure 71 GSM transmitter
RM-123; RM-145
Nokia Customer Care System Module
Page 8 –22 COMPANY CONFIDENTIAL Issue 1
Copyright © 2006 Nokia. All rights reserved.
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