RH-47
Company Confidential
7 - RF Description and Troubleshooting
Nokia Customer Care
Page 24
Copyright
©
2004 Nokia Corporation
Issue 1 05/04
Company Confidential
Figure 5: Rx signal paths
Antenna switch (RX/TX Switch)
Signal path of RF: From the antenna-pad (J800) the RF signal is fed through the antenna
low pass filter (C743, L610, C748) to the antenna switch (Z601).
The antenna switch has the function of a diplexer which consists of two paths for
GSM850 and GSM1900. The GSM850 input signals pass the switch to the GSM_RX out-
put. GSM1900 input signals pass to PCS_RX output. In receive mode both control signals
VC1 (VANTL) and VC2 (VANTH) have to be 0 V.
Signal paths:
GSM850: RX1-GSM output of the antenna switch
Æ
GSM850 SAW filter (Z604).
GSM1900: RX2-PCS output of the antenna switch
Æ
GSM1900 SAW filter (Z603).
The antenna switch including routed lines has following typical insertion losses:
GSM850: 1.3dB
GSM1900:
1.6dB
RX front-end
The RX front-end includes two SAW filters for GSM850 (Z604) and GSM1900 (Z603).
They are matched to the corresponding LNA inputs of Mjoelner RF ASIC (N601) with dif-
ferential matching circuits (LC-type). The SAW filters provide out-of-band blocking
immunity. The integrated LNAs provide the front-end gains. Each of the SAW filters has a
single-ended input and a balanced output.
The SAW filters have maximum insertion losses of:
GSM850: 3.5dB
GSM1900:
4.0dB
1/2
1/4
2
2
2
2
INPL
INML
INPM
INMM
RXQP
RXIP
LPF1
DCN1
RF
Controls
RF
Controls
VANTL /
VANTM
BBAMP
BBAMP
SAW
SAW
Ant
S
w
it
c
h
RX
RX
TX
TX
PCN
GSM
V
D
D
R
X
B
B
Mjølner
VRX
INPH
INMH
AGC
LPF2
RXIM
LPF1
DCN1
AGC
LPF2
RXQM
2
VDDLO
V
D
D
R
X
F
RX850
RX1800
RX1900
BIQUAD
BIQUAD
DCN2
DCN2
LNA
LNA
LNA
Pre-gain
Pre-gain
Rx
supply
filter
VR6
VANTH
VDDDIG
LNA
Bias
2
VDDRXBB