Nokia 6020b Service Manual
Issue 1 03/2005
COMPANY CONFIDENTIAL
49
Copyright © 2005 Nokia. All Rights Reserved.
RM-31
7 - System Module
7 - System Module
Nokia Customer Care
To switch the TX-GSM1800/1900 path both signals VANT2 and VANT3 have to be activated.
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 sep-
arate 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.
signal is fed to the antenna switch module where a diplexer first divides the signal to two sep-
arate 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 component, the
other two LNAs are integrated in the RF ASIC.
band pass on to the low noise amplifiers. The GSM1900 LNA is an external component, 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 con-
verter in UEM for further digital signal processing.
gain stage to an appropriate baseband level and passed on as I and Q signal to the A/D con-
verter 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 amplifiers of the power
control loop.
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 amplifiers of the power
control loop.
The power amplifier module contains power detectors. In GMSK mode, the power is controlled
by adjusting the DC bias levels of the power amplifiers. In EDGE mode, the power is controlled
by adjusting ALC in Helgo RFIC.
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, GSM1800 and
GSM1900 bands, both RX and TX range. The frequency synthesizer is integrated in the RF
ASIC (Helgo) except for the VCTCXO, VCO, and the loop filter.
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, GSM1800 and
GSM1900 bands, both RX and TX range. The frequency synthesizer is integrated in the RF
ASIC (Helgo) except for the VCTCXO, VCO, and the loop filter.
VANT_2
VC1
[Volt]
VANT_3
VC2
[Volt]
VANT_1
VC3
[Volt]
Rx1
GSM
850
Rx
Rx2
GSM
1800
Rx
Rx3
GSM
1900
Rx
Tx1
GSM
850
Tx
Tx2
GSM
1800/1900
Tx
0
0
0
X
0
0
0
X
0
2.6
2.6
X
0
2.6
0
X
2.6
2.6
0
X