Nokia 9110 Service Manual
PAMS
Technical Documentation
RAE–2
BS8_RF
Page 3 – 16
Original 02/99
Figure 2.
Power control feedback loop
PA
DIR.COUPLER
DETECTOR
ERROR
AMPLIFIER
RF_OUT
RF_IN
TXC
R1
R2
DOMINATING
POLE
POLE
K
K
K
K
det
cp
PA
= –R1/R2
C
R
AGC strategy
The AGC–amplifier is used to maintain output level of the receiver almost
constant.
constant.
AGC has to be set before each received burst, this is called pre–monitor-
ing. The receiver is switched on before the burst begins, the DSP mea-
sures received signal level and adjusts RXC, which controls RX AGC–
amplifier or it switches off the LNA with PDATA0 control line. This pre–
monitoring is done in three phases and this sets the settling times for RX
AGC. Pre–monitoring is required because of linear receiver, received sig-
nal must be in full swing, no clipping is allowed and because DSP doesn’t
know, what is the level going to be in next burst.
ing. The receiver is switched on before the burst begins, the DSP mea-
sures received signal level and adjusts RXC, which controls RX AGC–
amplifier or it switches off the LNA with PDATA0 control line. This pre–
monitoring is done in three phases and this sets the settling times for RX
AGC. Pre–monitoring is required because of linear receiver, received sig-
nal must be in full swing, no clipping is allowed and because DSP doesn’t
know, what is the level going to be in next burst.
There is at least 60 dB accurate gain control ( continuous, analog ) and
one digital step in LNA. It is typically about 30...35 dB.
one digital step in LNA. It is typically about 30...35 dB.
RSSI must be measured on range –48...–110 dBm. After –48 dBm level
MS reports to base station the same reading.
MS reports to base station the same reading.
Because of RSSI–requirements, gain step in LNA is used roughly on –45
dBm RF–level and up to –10 dBm input RF–level accurate AGC is used
to set RX output level. LNA is ON ( PDATA0 = ”0” ) below –47 dBm. from
–47 dBm down to –95 dBm
dBm RF–level and up to –10 dBm input RF–level accurate AGC is used
to set RX output level. LNA is ON ( PDATA0 = ”0” ) below –47 dBm. from
–47 dBm down to –95 dBm
This accurate AGC in SUMMA is used to adjust the gain to desired value.
RSSI–function is in DSP, but it works out received signal level by measur-
ing RX IQ–level after all selectivity filtering ( meaning IF–filters,
RSSI–function is in DSP, but it works out received signal level by measur-
ing RX IQ–level after all selectivity filtering ( meaning IF–filters,
Σ∆±
con-
verter and FIR–filter in DSP). So 50 dB accurate AGC dynamic range is