User Guide

Table Of Contents

Issue 2 10/2004 COMPANY CONFIDENTIAL 5

NHL-12

7 - RF Description & Troubleshooting Nokia Customer Care

1. RF Description and Troubleshooting

The RF module performs the necessary high frequency operations of the GSM850/1800/1900

tripleband (EDGE) engine. Both the transmitter and receiver have been implemented 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 component

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)

• Antenna switch module

• Four SAW filters

• Three transformer baluns

■ RF key component placement

Figure 1:RF key components

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 information 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 the UPP, Helgo controls itself to the required mode of op-

eration and further sends control signals to the front end and power amplifier modules. In ad-

dition to the RFBus, there are still other interface signals for the power control loop and

VCTCXO control and for the modulated waveforms.