Rf In General - Nokia NEM-4 Series Troubleshooting Instructions

NEM-4
RF Troubleshooting

RF in general

The RF part is a triple-band direct conversion transceiver. Using direct conversion no
intermediate frequencies are used for up- or down- conversion.
The VCO is set to either twice or four times (depending on the band used) the wanted RX
or TX frequency. The VCO frequency is divided by either 2 or 4 and fed to the mixers
(down-conversion) or modulators (up-conversion). Up- or down- conversion is done in
one step, directly between RF frequency and DC. All up and down-conversion takes place
in the RF ASIC named Mjoelner (N601).
Mjoelner RF ASIC also contains PLL and LNAs for all used bands. A DC control section is
included in to power and/or control EGSM TX buffer, detector and antenna switch. The
Mjoelner RF ASIC is controlled via a serial bus.
Mjoelner RF ASIC contains an integrated VCXO which uses an external 26 MHz Xtal. No
analogue AFC signal is needed. AFC is done via the serial interface of Mjoelner.
The interface between Mjoelner RF ASIC, UPP and Bluetooth uses a 26 MHz reference
clock. An external 26 MHz reference clock buffer is used to drive Bluetooth module.
The RF supports HSCSD (High Speed Circuit Switched Data) and GPRS (General Packed
Radio Service), meaning multi-slot operation, this will not require special equipment or
procedures in repair situations.
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Company Confidential
Figure 7: Tx measurement points inside Mjoelner can
Copyright  2003 Nokia Corporation
Company Confidential
CCS Technical Documentation
Issue 1 09/2003