User Guide

RM-4/RM-5
Engine Module CCS Technical Documentation
ISSUE 1 02/2004 COMPANY CONFIDENTIAL 33
Copyright © 2003 Nokia. All Rights Reserved.
General description of the RF circuits
In the following general description the different parts is described at block level.
Receiver signal path
The signal from the antenna pad is routed to the RX/TX switch (Z700). If no control voltages
are present at VANT2 and VANT1, the switch works as a diplexer and the GSM900 signal is
passed through the RX/TX switch to the GSM-RX and the GSM1800 signal to PCS-RX.
From the RX/TX switch, the GSM900 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 I Mjoelner
(N600) with a balanced signal. The front end of Mjoelner is divided into a LNA and a Pre-Gain
amplifier before the mixers.
The output from the mixer is fed to the baseband part of Mjoelner, where the signals are am-
plified in the BBAMP and lowpass filtered in LPF1 before the DC compensations circuits in
DCN1. The DCN1 output is followed by a controlled attenuator and a second lowpass filter
LPF2. The output from LPF2 is DC centered in DCN2 before being feed to the BB for demod-
ulation.
The GSM1800 signal chain is similar to GSM900, the SAW filter is numbered Z601.
Transmitter signal path
The I/Q signal from the BB is routed to the modulators for both 900 and 1800 MHz. The output
of the modulators is either terminated in a SAW filter (Z603) for GSM900 or a balun for
GSM1800.
The signal is then amplified in the PA (N700) where the gain control takes place. The TX signal
from the couplers is fed to the RX/TX switch, used to select which signal to route to the antenna.
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NDIV
ADIV
ϕ
charge
pump
RDIV
1/2
1/4
CPOUT
2
2
2
2
1/2
1/4
loop
filter
26MHz
INPL
INML
INPM
INMM
RXQP
RXIP
LPF1
DCN1
PWC
RBEXT
RF
Controls
RF
Controls
VANT1 / VANT2
VXO
BBAMP
BBAMP
SAW
TXC
TXP
RESET_X
Ant Switch
RX
RX
TX
TX
PCN
GSM
V
D
D
R
X
B
B
Mjoelner
Buffer
VBEXT
VRX
INPH
INMH
AGC
LOCNT
REFCNT
Lock
detect
TXIP/TXIM
TXQP/TXQM
2
2
2
2
2 2 2 2
XTALM
XTALP
REFOU
T
2
2
LPF2
RXIM
LPF1
DCN1
AGC
LPF2
RXQM
2
2
VPLL
VDDCP
VDDPRE
LO
buffer
VDDLO
VDDPLL
V
D
D
R
X
F
VDDXO
VREF1
VDDDL
VDDDIG
VDDBBB
VBB
CTRL
VTX
RX900/850
RX1800
RX1900
BIQUAD
BIQUAD
2,7k
DCN2
DCN2
TXC
TXP
SENSE
VCP
RESETX
VCCVCO1
VCCVCO2
VVCO
VDDTX
Hitachi PA: 33k
Philips PA: 56k
RFMD PA: 82k
REFOUT
RFBUSCLK
RFBUSX
RFBUSDA
3
SAW