General Description Of The Rf Circuits; Receiver Signal Path - Nokia NPM-10 Series Troubleshooting Instructions

NPM-10
Troubleshooting Instructions RF
• LF (Low frequency) and DC measurements should be done with a 10:1
probe and an oscilloscope. The probe used in the following is 10MΩ/
8pF passive probe. If using another probe, then bear in mind that the
voltages displayed may be slightly different.
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 realign-
ing the phone.
Most RF semiconductors are static-discharge sensitive. ESD protection must be taken
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
if soldering of the component is done properly and checking if the component is missing
from PWB. Capacitors can be checked for short-circuiting and resistors for value by
means of an ohmmeter, but be aware that in-circuit measurements should be evaluated
carefully.
In the following, both the name GSM and GSM850 will be used for the lower band and
both PCS and GSM1900 will be used for the upper band.

General Description of the RF Circuits

In the following general descriptions, different colors are used in the block diagram. The
GSM850 signal route is shown in red, the GSM1900 route in green, and the common sig-
nal lines are shown in blue. Control, supply voltage, and unused lines are shown in black.

Receiver Signal Path

The signal from the antenna pad is routed to the Antenna switch (Z700). If no control
voltage is present at VANT2 and VANT1, the switch works as a diplexer for the RX signal:
the GSM850 signal passes through the switch to GSM RX and the GSM1900 signal
passes through the switch to PCS RX.
ANTENNA
SAW
SWITCH
Z602
Z700
INPL
RX850
RX
INML
GSM
TX
INPM
RX
RX1900
PCS INMM
SAW
Z601
TX INPH
RX1800
INMH
2
2
VANTL / VANTM
Page 6
FILTER
LNA
PRE-
BIAS
GAIN
LNA
LNA
PRE-
GAIN
2
LNA
1/2
VDDDIG
RF
CONTROLS
Figure 1: Receiver signal path
Nokia Corporation
CCS Technical Documentation
DCN1
LPF1
BBAMP
LPF1
BBAMP
DCN1
2 2 2
1/4
Confidential
VR6
LPF2
AGC
BIQUAD DCN2
RXIP
RXIM
RXQP
DCN2
RXQM
LPF2
AGC
BIQUAD
Mjoelner
N600
Issue 1 03/2003