Introduction To Rf - Nokia RH-47 Series Rf Description And Troubleshooting

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RH-47

7 - RF Description and Troubleshooting

Introduction to RF

The RF front-end is a dual-band direct conversion transceiver. Using direct conversion, no

intermediate frequencies are used for up- or down -conversions.

The VCO oscillates on the doubled respectively quadruplicated frequency of the wanted

RX or TX frequency, depending on the band used. 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 base band. 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. ADC control section is

included to power and/or control GSM850 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 realized via the serial interface port of Mjoelner.

The UPP is supplied by the 26 MHz reference clock of Mjoelner.

The phone supports GPRS (General Packet Radio Service), meaning multi-slot operation.

This will not require special equipment or procedures in repair situations.

The following diagrams show the RF frequency scheme and the RF block diagram.

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