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Nokia Customer Care
22
COMPANY CONFIDENTIAL
Issue 2 06/2005
Copyright © 2005 Nokia. All Rights Reserved.
General description of the RF circuits
In the following general desriptions different colours are used in the block diagram. The Low-
band signal route is shown in red, the Highband route in green and the common signal lines
are shown in blue.
■
Receiver signal path
The signal from the antenna pad is routed to the Front End Module (FEM - N700). The FEM
contains a diplexer and a switch system controlling the direction of the signals, either routing
the TX signal from the Power Amplifier (PA) to the antenna or routing the received signal from
the antenna to either the Lowband (850/900 MHz) or the Highband (1800/1900 MHz) input on
the RF IC (N600).
Figure 14:Receiver signal path
The Lowband signal from the FEM is routed to the SAW filter (Z602). The purpose of the SAW
filter is to provide out-of band blocking imummity and to provide the LNA in Mjoelner (N600)
with a balanced signal. The front end of Mjoelner is divided into a LNA and Pre-Gain amplifier
before the mixers.
The output from the mixer is fed to Baseband part of Mjoelner where the signals amplified in
the BBAMP aand low pass filteret in LPF1 before the DC compensation circuits in DCN1. The
DCN1 output is followed by a controlled attenuator and a second lowpass filter LPF2. The out-
put from LPF2 is DC centeret in DCN2 before being feed to the BB for demodulation.
The Highband signal chain is similar to the lowband.
■
Transmitter signal path
The I/Q signal from the BB is routed two the modulators for both Lowband and Highband. The
output of the modulators is either terminated in a SAW filter (Z603) for the Lowband or a balun
for the Highband. The signals from the SAW and Balun are then amplified in the Power Ampli-
fier (PA) located in the Front End Module (FEM - N700) where the gain control takes place. In
INPL
INML
INPM
INMM
RXQP
RXIP
V
D
D
R
X
B
B
Mjølner
VRX
INPH
INMH
RXIM
RXQM
Rx
supply
filter
VR6
SAW
RX850/
900
SAW
RX1800/
1900
1/2
1/4
2
2
2
2
1/2
1/4
LPF1
DCN1
BBAMP
BBAMP
AGC
LPF2
LPF1
DCN1
AGC
LPF2
V
D
D
R
X
F
BIQUAD
BIQUAD
DCN2
DCN2
LNA
LNA
LNA
Pre-gain
Pre-gain
LNA
Bias
Diplexer
RX/TX switch
PA and detector
Ant
GSM RX
PCS RX
ASIC
