Cmt Rf; Top-Level Description - Nokia RA-8 Rf Description And Troubleshooting

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RA-8

7 - RF Description and Troubleshooting

CMT RF

The RF module performs the necessary high frequency operations of theEGSM900/1800/1900

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, Honi. Another core component

is a power amplifier module which includes two amplifier chains, one for EGSM900 and the oth-

er for GSM1800/GSM1900.

Other key components include

• 26 MHz VCTCXO for frequency reference

• 3296-3980 MHz SHF VCO (super high frequency voltage controlled oscillator)

• Antenna switch module (ASM)

• Three SAW filters

• BAW-LNA module

The control information for the RF is coming from the baseband section of the engine through

a serial bus, referred later on as RFBus.

The whole RF circuitry is located on one side of the 8-layer PWB.

EMC leakage is prevented by using a metal shield with gasket. The RF circuits are separated

into two blocks.

• PA, ASM, TK balun

• Honi RF IC, VCO + balun, VCTCXO, BAW-LNA, Rx filter, Tx filter

The RF transmission lines constitute of striplines and microstriplines after PA.

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