User Guide

RH-37
System Module Nokia Customer Care
Page 52 Nokia Corporation Issue 1 07/04
To switch the TX-GSM 1800/1900 path both signals VANT2 and VANT3 have to be acti-
vated.
Receiver
Each receiver path is a direct conversion linear receiver. From the antenna, the received
RF signal is fed to the antenna switch module where a diplexer first divides the signal to
two separate paths for the low band and the two high bands. Then the paths are passing
the Rx/Tx switches and the high band signal passes an additional GSM1800/1900 switch.
As output of the module three separate Rx connections are available.
These signals are fed to the SAW band filters, which let only the frequencies of the
wanted band pass on to the low noise amplifiers. The GSM1900 LNA is an external com-
ponent, the other two LNAs are integrated in the RF ASIC.
The received signal is down converted in the demodulator mixers and amplified in the
AGC gain stage to an appropriate baseband level and passed on as I and Q signal to the
A/D converter in UEM for further digital signal processing.
Transmitter
The transmitter consists of two final frequency IQ-modulators and a power amplifier
module with separate paths for the lower band and the upper bands, and a power control
loop. The IQ-modulators are integrated in the RF ASIC, as well as the operational ampli-
fiers of the power control loop.
The power amplifier module contains power detectors. In GMSK mode, the power is con-
trolled by adjusting the DC bias levels of the power amplifiers. In EDGE mode, the power
is controlled by adjusting ALC in Helgo RFIC.
Frequency synthesizer
One PLL synthesizer generates all the required frequencies of the three bands for Rx and
Tx operation. The VCO frequency is divided by 2 or by 4 in the RF ASIC depending on the
active band. This allows the generation of all the frequencies in the GSM850, GSM900,
GSM1800 and GSM1900 bands, both RX and TX range. The frequency synthesizer is inte-
VANT_2
VC1
[Volt]
VANT_3
VC2
[Volt]
VANT_1
VC3
[Volt]
Rx1
GSM
900
Rx
Rx2
GSM
1800
Rx
Rx3
GSM
1900
Rx
Tx1
GSM
900
Tx
Tx2
GSM
1800/1900
Tx
000X
000 X
02.62.6 X
02.60 X
2.6 2.6 0 X