Pll - Nokia NPM-10 Series Troubleshooting Instructions

NPM-10
Troubleshooting Instructions RF
Ant.
switch
2
Z700
RX
L704
GSM
TX
Dir.
coupler
RX
L709
PCN
TX
DET

PLL

The PLL supplies Local Oscillator (LO) signals for the RX and TX mixers. In order to be able
to generate LO frequencies for the required GSM and PCS channels, a regular Synthesizer
circuit is used. All PLL blocks except for the VCO, reference X-tal, and loop filter are
located in the Mjoelner IC.
The reference frequency is generated by a 26MHz Voltage Controlled X-tal Oscillator
(VCXO), which is located in Mjoelner. Only the X-tal is external. 26MHz is supplied to BB
where a divide-by-2 circuit (located in the UPP IC) generates the BB clock at 13MHz. The
reference frequency is supplied to the reference divider (RDIV) where the frequency is
divided by 65. The output of RDIV (400kHz) is used as reference clock for the Phase
Detector (ϕ).
The PLL is a feedback control system controlling the phase and frequency of the LO sig-
nal. Building blocks for the PLL are: Phase detector, Charge Pump, Voltage Controlled
Oscillator (VCO), N-divider, and loop filter. As mentioned earlier only the VCO, reference
X-tal, and loop filter are external to the Mjoelner IC.
The VCO (G600) is the component that actually generates the LO frequency. Based on the
control voltage input, the VCO generates a differential RF output. This signal is fed to the
Prescaler and N-divider in Mjoelner, these two blocks will together divide the frequency
Page 8
VANTL / VANTM
2
VANTH
VB_DET
VTXLOL
VTXLOH
VTXBH
VTXBL
PCS
Balun
V701
Buffer
VTX
PA
N700
SAW Z603
Buffer
GSM
V702
Loop
filter
2
VBATTRF
Figure 2: Transmitter signal path
Nokia Corporation
CCS Technical Documentation
VDDDIG
RF
Controls
VDDRXBB
RF
Controls
OUTHP
OUTHM
OUTLP
OUTLM
DET
PLFB1
PWC
PLFB2
VPCH/VPCL
Supply
filter
TXP
TXC
VR2
Confidential
1/2
1/4
2 2
2 2
Mjoelner
N600
2 2
Issue 1 03/2003