User Guide
CCS Technical Documentation 7 - System Module & UI
Company Confidential NMM-3
Issue 1 (11/2003) Copyright 2003 Nokia Corporation Page 7-43
Company Confidential
The differential IQ signals from TIKU to TEX are in current mode. Before any processing
can be done they are converted to voltage mode by a current to voltage (I/V) converter .
Analog BB filtering (WCDMA and GSM) is then applied in TEX. The MUX (multiplexer)
switches the IQ signals to either WCDMA or GSM signal paths depending on which mode
is selected. After modulation the WCDMA signal is amplified by the AGC stage in TEX.
From TEX the differential signal is routed to the AGC driver amplifier HEX. The AGC
topology of HEX is very similar to TEX only the output signal level is higher. The gain of
HEX and TEX is controlled by TXA1 and TXA2 signals coming from 10bit Dacs in TIKU.
Both AGCs have about 50 dBs of dynamic range.
Before the PA the signal is filtered in a TX SAW filter. After filtering the signal is fed to
the two stage class AB PA. The PA bias current is coming partly from UEME (IPA1 4 bits
DAC) and partly from the TX feedback loop (PAbias). The value of IPA1 (fixed) is cali-
brated on production alignment. The feedback loop current PAbias varies depending on
the output power level set. The feedback loop current is generated by measuring the
voltage level at the output of the detector. This voltage is then converted to a current in
TEX and then added to the IPA1 control current.
The supply voltage to the PA varies depending on the output power level set. This is done
to minimize the current consumption of the PA at lower power levels. The TXC signal
from UEME is used to control output voltage of the PA SMPS (Switch Mode Power Sup-
ply). The supply voltage varies from 3.5V at 21dBm down to 1.5V at an ouput power
≤10dBm.
The isolator between PA and duplexer ensures that the output load of the PA does not
vary much thus restricting ACLR (Adjacent Channel Leakage power Ratio) variations
under mismatch conditions.
The power detector is needed
• to detect the suitable PA bias current
• to detect the max TX power (limit the max TX power)
• to detect the highest 10 dB power levels
TX power control
Open loop power control is used when creating a call (sending RACH signals). The trans-
mitted signal level is estimated from the received signal level. The accuracy demand cov-
ering RX and TX is ± 12 dB in extreme conditions.
In call mode the base station is adjusting the output power of the mobile upwards or
downwards (inner loop power control). The nominal power control steps sizes are ± 1…
±3 dB.
The defined TX dynamic range is 71 dB (21… -50 dBm). Taking into account the gain vari-
ations of the hardware in extreme conditions the TX dynamic range is actually 100 dB.
The whole dynamic range is divided fifty-fifty between the AGC stages in TEX and HEX.
The gain curves of both AGC stages are calibrated (modeled) in production alignment.
The TX power control algorithm calculates using two separate gain curves one common