Nokia 9210i Servicehandbuch

PAMS

Technical Documentation

RAE-5 

3. RF+System Module KL8 

Page 3 – 47

Issue 1 04/02

VCO frequency is locked with PLL into stable frequency source, which is a
VCTCXO–module . The VCTCXO is running at 26 MHz.  The residual tempera-
ture, drift, Doppler and initial inaccuracy effects are compensated with AFC (
automatic frequency control ) voltage. The AFC locks the VCTCXO into fre-
quency of the base station

PLL is located in HAGAR RF–IC and is controlled via serial bus from MADLin-
da–IC, which is located in the system block.

LO–signal is generated by SHF VCO module. VCO has double frequency in
DCS1800 and x 4 frequency in E–GSM compared to actual RF channel fre-
quency. LO signal is divided by two or four in HAGAR (depending on system
mode).

Receiver is a direct conversion, dualband linear receiver.  Received RF–signal
from the antenna is fed via RF–antenna switch to 1st RX dualband SAW filter
and discrete LNAs (low noise amplifier). There are separate LNA branches for
EGSM900 and DCS1800.

After the LNA amplified signal ( with low noise level ) is fed to bandpass filter
(2nd RX dualband SAW filter).

These bandpass filtered signals are then balanced with baluns. Differential RX
signal is amplified and mixed directly down to BB frequency in HAGAR. Local
oscillator  signal is generated with external VCO. VCO signal is divided by 2
(DCS1800) or by 4 (EGSM900). PLL and dividers are in HAGAR–IC.

From the mixer output to ADC input RX signal is divided into I– and Q– signals.
Accurate phasing is generated in LO dividers. After the mixer DTOS amplifiers
convert the differential signals to single ended.

Next stage in the receiver chain is AGC–amplifier, also integrated into HAGAR.
AGC has digital gain control via serial mode bus from MADLinda IC.

Single ended filtered I/Q–signal is then fed to ADCs in COBBA–IC. Input level
for ADC is 1.4 Vpp max.

Transmitter chain consists of final frequency I/Q–modulator, dual–band power
amplifier and a power control loop.

I– and Q–signals are generated by baseband also in COBBA_GJP ASIC. After
post filtering ( RC–network ) they go into IQ–modulator in HAGAR.  After modu-
lator the TX–signal is amplified and buffered. There are separate outputs for
both E–GSM and DCS1800. HAGAR TX output level is +3 dBm minimum at 2.8
V modulator supply voltage.

Next TX signals are converted to single ended by discrete baluns. EGSM and
DCS1800 branches are combined with diplexer.

The final amplification is realized with dual–band power amplifier.  It has one 50
ohm input and two 50 ohm outputs.  PA is able to produce over 3 W (4.5 dBm