Nokia RH-29 Series Manual page 20

RH-29
6b - RF Troubleshooting
(top).
GSM900 TX path of Mjoelner RF ASIC
The balanced TX signal is provided by the base band and is coming to the Mjoelner RF
ASIC. The TX paths of the Mjoelner RF ASIC include mainly two RF modulators for up-
conversion of the base band signals, one for GSM900 and one for GSM1800. The base
band signal is modulated with the LO signal corresponding to the wanted TX channel.
The GSM TX output of the Mjoelner RF ASIC is a balanced signal.
From the output of the Mjoelner RFASIC the signal is fed through the 900 TX SAW filter
(Balanced to single ended), the 900 MHz buffer, and a 5 dB pad to the PA input.
GSM900 TX path of the Power Amplifier (PA)
The PA GSM900 part has a minimum stable output power of app. 35 dBm. Voltage supply
is coming directly from the Battery connectors.
The GSM900 output is controlled by the power control loop. From the GSM900 output of
the PA the RF signal is fed through the directional coupler (one of the power control loop
components) to the antenna switch.
Antenna Switch (TX/RX switch)
The antenna Switch works as a diplexer for the RX and TX signals. Moreover, it sup-
presses the TX harmonics generated by the PA. The antenna switch is controlled by the
Mjoelner RF ASIC using the control signals Vcont1 and Vcont2. The following table
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