User Guide

NPM-10 (3595)
Troubleshooting - RF CC Technical Documentation
Page 4 ©2004 Nokia Corporation Confidential Issue 2 03/2004
Always make sure the measurement set-up is calibrated when measuring RF parameters
on the antenna pad. Remember to include the loss in the module test jig when realigning
the phone.
Most RF semiconductors are static-discharge sensitive. Use ESD protection during
repair (ground straps and ESD soldering irons). Mjoelner is moisture-sensitive, so parts
must be pre-baked prior to soldering.
Apart from key components described in this section, there are a lot of discrete compo-
nents (resistors, inductors, and capacitors) for which troubleshooting is done by checking
whether the soldering of the component is done properly, and whether the component is
missing from the PWB. Capacitors can be checked for short-circuits and resistors for
value by means of an ohmmeter, but be aware that in-circuit measurements should be
evaluated carefully.
In this chapter, both GSM and GSM 850 will be used for the lower band and both PCS
and GSM 1900 will be used for the upper band.
General Description of the RF Circuits
Figure 1 and Figure 2 include different colors in the block diagrams. The GSM 850 signal
route is red, the GSM 1900 route is green, and the common signal lines are blue. Control,
supply voltage, and unused lines are shown in black.
Receiver Signal Path
The signal from the antenna pad is routed to the front end module (N700). The GSM 850
signal passes through the switch inside the FEM to TGSM_Rxout, and the GSM 1900
signal passes through the switch inside the FEM to PCS_Rxout.
Figure 1: Receiver signal path
From the FEM PA, the GSM 850 signal is routed to the SAW filter (Z602). The purpose of
the SAW filter is to provide out-of-band blocking immunity and to provide the LNA in
Mjoelner (N600) with a balanced signal. The front end of Mjoelner is divided into an LNA
and a pre-gain amplifier before the mixers.
1/
2
1/
4
2
INP
L
INM
L
INP
M
INM
M
RXQ
P
RXI
P
VANTL / VANTM/ VANTH
SAW
Z60
2
SAW
Z60
1
R
X
R
X
T
X
T
X
PC
S
GSM
V
D
D
R
X
B
B
Mjoelner
N600
VR
X
INP
H
INM
H
RXI
M
RXQ
M
3
V
D
D
R
X
F
RX85
0
RX190
0
VR
6
VDDDI
G
3
LN
A
PRE
-GAI
N
LN
A
BIA
S
R
XSUPPL
YFILTE
R
BBAM
P
LPF
1
FEM
N700
LN
A
LN
A
DCN
1
AG
C
LPF
2
BIQUA
D
DCN
2
RX180
0
222
LPF
2BIQUA
D
DCN
2
BBAM
P
LPF
1
DCN
1
AG
C
R
FCONTROL
S
PRE
-GAI
N