Samsung SPH-A900 Service Manual page 8

Circuit Description
2-1-4. RF Interface Part
CDMA Data Interface
- TX_Q_P, TX_Q_N, TX_I_P, TX_I_N (U402) : Tx analog signal used during CDMA
- RX_I_P, RX_Q_P, RX_I_N, RX_Q_N (U301) : RX analog signal used during CDMA
RF Interface
- TX : TX_AGC_ADJ(ucp102) is used to control the TX power,
PA_ON_PCS(ucp102) is used to control the PCS power amplifier and
PA_ON_CELL(ucp102) is used to control the CDMA power amplifier.
- RX : TRK_LO_ADJ(ucp102) is used to adjust the TCXO module.
2-1-5. Audio Part
The MSM6500 device integrates a stereo wideband voice/audio CODEC into the Mobile Station Modem.
The integrated CODEC contains all of the required conversion and amplification stages for the
audio front end.
The CODEC operates as a 13bit linear CODEC with the transmit(TX) and receive(RX) filters designed
to meet ITU-T G.712 requirements. The CODEC contains the software controlled amplifier for both the
receiving and transmitting sections. Also, the vocoding schemes used will be 13kbps QCELP and 8Kbps
EVRC. The QCELP vocoder is based in the MSM internally.
2-1-6. Tx Audio Path
The voice signal from the microphone is filtered and amplified by the internal OP-AMP and is converted
to PCM data by the internal CODEC in the MSM. And then these signals are applied to the the
MSM(ucp102)'s internal vocoder.
2-1-7. Rx Audio Path
The PCM data from the MSM(ucp102) is inputted to the internal CODEC and the data will be decoded
by the internal DAC. Audio levels are adjusted by the amplifier. And then audio is sent to the receiver.
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