User Guide

NMM-3 Company Confidential
7 - System Module & UI CCS Technical Documentation
Page 7-44 Copyright  2003 Nokia Corporation Issue 1 (11/2003)
Company Confidential
gain curve for both AGCs covering the entire dynamic range. This ensures that when the
TX power level is changed both AGCs are adjusted simultaneously.
WCDMA receiver
Figure 8: WCDMA RX block diagram
The receiver is based on direct conversion architecture.
The received RF-signal is fed from the WCDMA antenna to the duplexer. In a WCDMA
system both the receiver and transmitter are on at the same time. The main function of
the duplexer is to filter the signal and noise of its own transmitter from the received sig-
nal. The typical attenuation for TX noise in the RX band is 45 dB and to the TX signal is
50 dB.
After filtering the signal is converted from single-ended to differential using a balun. The
differential signal is then fed to the integrated LNA in REX. The LNA has three gain steps.
The maximum gain step is 18dB, the middle is 6 dB and the lowest is –9dB. The LNA gain
is controlled via RFBus. The current consumption of the LNA can be dropped to half its
nominal value depending on the defined received signal strength level. The drawback of
this is that it affects the LNA gain. This effect is calibrated for in production alignment.
After amplifying the signal is routed out from REX to the SAW filter. The main function of
the RX band filter is to filter out more of the TX signal and to improve the out of band
attenuation performance. The attenuation of the duplexer to frequency ranges outside of
its own band can be very low. The RX SAW filter improves the out of band attenuation to
guarantee the required attenuation for out of band blocking signals.
Duplexer
TX signal
WRXI_P
WRXI_N
WRXQ_P
WRXQ_
N
Balun
RXVCO
Balun
REX
ANT signal
2
PLL
IQ demodulator