Fig 29 Simplified Synthesizer - Nokia RH-9 Series Ccs Technical Documentation

RH-9
System Module & UI
The receiver selectivity for out-of-band signals is defined by the RF front-end SAW filter.
The receiver ability to withstand large out-of-band signals is defined by the RF SAW fil-
ter and the large signal behavior of the LNA – pregain and mixer.
The inband selectivity is define by the 91 kHz channel filters in Mjoelner, and the in-band
large signal behavior is a combination of the RF front-end and the BB amplifier large sig-
nal behavior.
AGC
As the receiver is a linear type the AGC must keep the BB level form the receiver within a
certain range in order to stay within the dynamic range for the BB, even during fading.
The AGC has to be set before each received burst with pre-monitoring or without pre-
monitoring. In pre-monitoring, receiver is switched on roughly 130µs before the burst
begins, DSP measures received signal level and adjusts AGC-amplifiers via the serial bus.
RSSI must be measured accurately on range -48...-110 dBm. After -48 dBm level MS
reports to base station the same reading.
The AGC is a combination of gain controlled elements at both RF and BB frequencies.
In RF it is the LNA which is used as an AGC element with one step. The AGC step size of
the LNA will have different values between 900 MHz and 1800 MHz as well across the
band.
In BB the AGC has 12 steps, a combination of DCN_1 and AGC, with a resolution of ~6
dB giving a total BB AGC range of 72 dB.
mV
1350
1270
1000
360
316
100
32
10
3.2
-110 -100
DC-compensation
Page 80
Figure 31: Gain control
HW limit
DSP clip limit
Phone shall report RX-level accurately
Accurate Gain range (calibrated)
-90 -80 -70
ãNokia Corporation
CCS Technical Documentation
10 dB fading margin
LNA ON LNA OFF
Phone shall report a constant RX-level (63)
-60 -50 -40 -30
dBm
-48 dBm
dB/mV
62
60
53
50
6 dB
47
40
30
20
10
-20 -10
Issue 1 11/02