Nokia 6020b Service Manual
RM-31
Nokia Customer Care
7 - System Module
50
COMPANY CONFIDENTIAL
Issue 1 03/2005
Copyright © 2005 Nokia. All Rights Reserved.
The VCTCXO (Voltage Controlled Temperature Compensated Crystal Oscillator) generates the
clock frequency of 26 MHz. This frequency is buffered in the RF ASIC and fed to the UPP. Ad-
ditionally, it is used as the reference frequency for the RF PLL. The frequency of the VCTCXO
is locked into the frequency of the base station with the help of an AFC voltage which is gener-
ated in the UEM by an 11 bit D/A converter.
clock frequency of 26 MHz. This frequency is buffered in the RF ASIC and fed to the UPP. Ad-
ditionally, it is used as the reference frequency for the RF PLL. The frequency of the VCTCXO
is locked into the frequency of the base station with the help of an AFC voltage which is gener-
ated in the UEM by an 11 bit D/A converter.
The PLL (phase locked loop) locks the VCO frequency into a stable frequency source, given
by the VCTCXO. The PLL is located in the RF ASIC and is controlled through the RFBus.
by the VCTCXO. The PLL is located in the RF ASIC and is controlled through the RFBus.
The loop filter generates a DC control voltage for the VCO from the charge pump pulses of the
phase detector. The loop filter determines the step response of the PLL (settling time) and con-
tributes to the stability of the loop.
phase detector. The loop filter determines the step response of the PLL (settling time) and con-
tributes to the stability of the loop.
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Signal paths
Receiver signal paths
From the antenna-pad, the RF signal is fed directly to the antenna switch module. Depending
on the control signals VC1, VC2, VC3, the antenna port is connected to one of the Rx ports
RX1, RX2, RX3. From these ports the signal is passed on to the band filters:
on the control signals VC1, VC2, VC3, the antenna port is connected to one of the Rx ports
RX1, RX2, RX3. From these ports the signal is passed on to the band filters:
• GSM850: RX1-> GSM850 SAW filter
• GSM1800: RX2 -> GSM1800 SAW filter
• GSM1900: RX3 -> GSM1900 SAW filter
The antenna switch has the following typical insertion losses in the Rx mode from its input to
output ports:
output ports:
• GSM850: 1.3 dB
• GSM1800: 1.6 dB
• GSM1900: 1.6 dB
LB LP
FILTER
VCO Module
VR7
2 dB
Att
Balun
900 Rx
SAW
1800 Rx
SAW
BUILT-IN DC COMP.
AND AGC FUNCTION
LOW-PASS FILTERS
INTEGRATED
VBB
1900 Rx
SAW
Balun
VBB
GPIO
10mA
2.7V
VLO
by 2/4
Divide
Serial
Bi-directional
Interface
ESD
HB BP
LC
900 Tx
LC
LC
1900 Tx
LC
SCLK
SLE
SDATA
RESET
CTRL inputs
VDIG
VRF_RX
VLNA
Rx part of RF ASIC
VRF_TX,VBB,VLO,VTX
RXIP
RXQP
VF_RX
VCP
VR1
VR2
VRF_TX
LNAB_P
LNA_P
VDIG
VR3
VF_RX
VPAB_VLNA
VRF_RX
VR4
VLO
VPRE
VR5
VBB
VR6
Antenna
Switch
Module
Switch
Module
Rx part of RF ASIC