User Guide

CC Technical Documentation Troubleshooting - RF
NPM-10 (3595)
Issue 2 03/2004 ©2004 Nokia Corporation Confidential Page 5
The output from the mixer is fed to the Mjoelner BB where the signal is amplified in the
BBAMP, and the low pass is filtered in LPF1 before the DC compensation circuits in
DCN1. The DCN1 output is followed by a controlled attenuator and a second low pass
filter (LPF2). The output from LPF2 is DC centered in DCN2 before being fed to the BB for
demodulation.
The GSM 1900 signal chain is similar to GSM 850, but the signal is routed through the
SAW filter (Z601).
Transmitter Signal Path
The I/Q signal from the BB is routed to the modulators for both 850 MHz and 1900 MHz.
The output of the modulators is either terminated in a SAW filter (Z603) for GSM 850 or
a balun (T602) for GSM 1900. The amplitude’s limited signal is then amplified in the PA
of the FEM (N700). The internal FEM detector, some discrete components, and the
Mjoelner IC (N600) make up the transmitter gain control circuitry. In order to establish
the right Tx output power level, a sample of the signal is taken from the FEM detector
and used in the gain control loop. The Tx signal from the FEM is routed to the antenna,
which depends on the internal switch setting of the FEM.
Figure 2: Transmitter signal path
PLL
The phase-locked loop (PLL) supplies local oscillator (LO) signals for the Rx and Tx mixers.
In order to generate LO frequencies for the required GSM and PCS channels, a regular
synthesizer circuit is used. All PLL blocks (except for the VCO, reference X-tal, and loop
filter) are located in the Mjoelner IC.
1/2
1/4
OUTHP
OUTHM
OUTLP
OUTLM
PWC
DET
VANTL / VANTM / VANTH
PA
TXC
TXP
VBATTRF
VTXLOL
TXIP/
TXIM
TXQP/
TXQM
2
2
2
2
2
2
3
PLFB1
PLFB2
VPCH/VPCL
2
SAW Z603
VTX
VTX
TXC
TXP
VDDT
X
Suppl
y
filter
VR2
VTXBH
VDDDIG
VDDRXBB
DET
RF
Controls
RF
Controls
Balun
Loop
filter
FEM N700
RX
RX
TX
TX
PCN
GSM
3
Mjoelner
N600
S
w
i
t
c
h