User Guide

NPL-3 Company confidential
System Module and User Interface CCS Technical Documentation
Page 38 ãNokia Corporation. Issue 1 3/03
RF Module Introduction
The RF module performs the necessary high frequency operations of the GSM850/1800/
1900 tripleband (EDGE) engine. Both the transmitter and receiver have been imple-
mented by using direct conversion architecture which means that the modulator and
demodulator operate at the channel frequency.
The core of the RF is an application-specific integrated circuit, Helgo. Another core com-
ponent is a power amplifier module which includes two amplifier chains, one for
GSM850 and the other for GSM1800/1900.
Other key components include
• 26 MHz VCTCXO for frequency reference
• 3290-3980 MHz SHF VCO (super high frequency voltage controlled oscillator)
• front end module comprising a RX/TX switch and two RF bandpass SAW filters
• three additional SAW filters
The control information for the RF is coming from the baseband section of the engine
through a serial bus, referred later on as RFBus. This serial bus is used to pass the infor-
mation about the frequency band, mode of operation, and synthesizer channel for the RF.
In addition, exact timing information and receiver gain settings are transferred through
the RFBus. Physically, the bus is located between the baseband ASIC called UPP and
Helgo. Using the information obtained from UPP Helgo controls itself to the required
mode of operation and further sends control signals to the front end and power amplifier
modules. In addition to the RFBus there are still other interface signals for the power
control loop and VCTCXO control and for the modulated waveforms.
RF circuitry is located on one side of the 8 layer PWB.
EMC leakage is prevented by using a metal cans. The RF circuits are separated to three
blocks.
• FM radio.
• PA, front end module, LNA and 1900 band SAWs.
• Helgo RF IC, VCO, VCTCXO, baluns and balanced filters.
The RF transmission lines constitute of striplines and microstriplines after PA.
The baseband circuitry is located on the one side of the board, which is shielded with a
metallized frame and ground plane of the UI-board.