Nokia Customer Care
7 - RF Description and Troubleshooting
Company Confidential
RH-47
Issue 1 05/04
Copyright
©
2004 Nokia Corporation
Page 37
Company Confidential
necessary AFC value is written into the RefOSCAFC register in Mjoelner.
VCO
The VCO is able to generate frequencies in the range of 3296.8 MHz to 3979.6 MHz
when the PLL is working properly. The frequency of the VCO signal is divided by 2 or by 4
in Mjoelner RF-ASIC. This allows the generation of all the frequencies in the GSM850
and the GSM1900 bands, both RX and TX.
The output frequency of the VCO is controlled by a DC voltage (VC) of the PLL loop filter.
The valid range of VC is 0.7V– 3.8V when the PLL is in steady state. The typical tuning
sensitivity is 240MHz/V. Even if the PLL is not working properly (VC outside the valid
range) a frequency at the output of the VCO can be detected between 3GHz and 4 GHz
(if the VCO itself is OK).
Troubleshooting for PLL synthesizer
It is important to note that the power supply of the VCXO (VR3) is only switched off in
the so-called ‘Deep Sleep Mode’ and the power supply of the VCO G701 (VR7) is switched
off in so-called ‘Sleep Mode’.