User Guide

RH-25
System Module CCS Technical Documentation
Page 32 ©Nokia Corporation Confidential Issue 1 10/2003
Note, that in this point, term linear means -33dB ACP. The required LO power is about
-6dBm. The LO signal is fed from Taco.
Before power amplifier RF signal is filter in band filter. The typical insertion loss is about
-2.7dB, and maximum less than -3.0dB. The input and output return losses are about
-10dB.
Power amplifier is 50W/50W module. It does not have own enable/disable control signal,
but it can be enabled by bias voltage and reference bias current signals. The gain window
is +27 to +31dB and linear output power is +30dBm (typical condition) with -28dB ACP.
The nominal efficiency is 50%.
PCS Band
At operation in PCS band, the IF signal is routed outside from Taco to be filtered in TX IF
strip filter, and after that back to Taco, to the up-converter mixer. The LO-signal to the
mixer is buffered and balanced inside Taco. The mixer output is enabled by TXP2 TX con-
trol signal. The maximum linear (balanced) RF signal level to 50W load is about +7dBm.
After Taco balanced RF-signal is single-ended in 1:1 balun and then filtered in SAW fil-
ter. The typical insertion loss is about -4.0dB, and maximum less than -5.0dB. This filter
hasrelatively high pass band ripple about 1.0-1.5dB, largest insertion being at high end
of the band. The input and return losses are about -10dB.
Power amplifier is 50W/50W module. It does not have own enable/disable control signal,
but it can be enabled by bias voltage and reference bias current signals. The gain window
is +31 to +36dB and linear output power is +30dBm (typical condition) with -28dB ACP.
The nominal efficiency is 40%.
Power Control
For power monitoring, there is a power detector module (PDM) build up from a (dual)
coupler, a biased diode detector and an NTC resistor. RF signals from both bands are
routed via this PDM. The RF isolation between couplers is sufficient not to loose filtering
performance given by duplex filters.
The diode output voltage and NTC voltage are routed to BB A/D converters for power
control purpose. The TX AGC SW takes samples from diode output voltage and compares
that value to target value, and adjust BB I-and Q-signal amplitude and/or Taco PGA set-
tings to keep power control in balance.
NTC voltage is used for diode temperature compensation and for thermal shut down
when radio board's temperature exceeds +85°C.
False TX indication is based on detected power measurement when carrier is not on.
The insertion loss of coupler is -0.42dB (max) at cellular band and -0.48dB (max) at PCS
band. Typical values for insertion losses are about -0.2dB. The filtering performance of
diplexer is taken in account in system calculations.