Antenna Switch Module - Nokia NPL-4 Series Manual

NPL-4/5/RM-104
System Module and User Interface
There are two different amplifier chains in a single amplifier module, one for GSM850/
EGSM900 and one for GSM1800/GSM1900. The lower band power amplifier is able to
deliver over 2 W of RF power, while the capability of the upper band amplifier is over 1
W.
In the GMSK mode the gain control is implemented by adjusting the bias voltages of the
first two transistor stages thereby reaching the dynamic range of over 70 dB.
After the power amplifier the signal goes through a low pass filter and a pin-diode
switch which is used to select between the reception and transmission. Finally, the two
signal paths, lower and upper band, are combined in a diplexer after which the signal is
routed through the antenna.
Power control circuitry consists of a power amplifier and an error amplifier. The power
amplifier produces a voltage level related to the value of the RF voltage. It is fed to the
negative input of the error amplifier where it is compared to the level of the reference
signal, TXC, obtained from UEMEK. Depending on the difference between the two signals
the biases of the power amplifier stages are either increased or decreased to get the cor-
rect power level out of the power amplifier.

Antenna switch module

The antenna switch module includes:
- Antenna 50 ohm input
- RX GSM850/900/1800/1900 single ended outputs,
- TXs EGSM900 and GSM1800/GSM1900 single 50 ohm input
-3 control lines from the Helgo
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