Samsung SCH-i830 Service Manual page 7

Circuit Description
Rx Audio Path
The PCM data from the MSM(UCP800)'s internal is inputted to the internal CODEC and the data will be
decoded by the internal DAC and audio levels are adjusted by the amplifier. The final audio is then sent
to the audio receiver.
2-2. PCS Section
2-2-1. Receiver
LOW NOISE AMPLIFIER (U1000)
The low noise amplifier(It is included in FC7510:U1000) amplifies a weak signal received from
the base station to obtain the optimum signal level.
RF BAND PASS FILTER (F1001)
The RF BPF(F1001) passes only a specific frequency(1960±30 MHz) from the signal received from the
mobile station. The bandwidth is 60 MHz.
VOLTAGE CONTROLLED OSCILLATOR(VCO1000)
The VCO(VCO1000) generates the signal having center frequency 1715 ~ 1788MHz frequency
range with the voltage control. The PLL in RTR6300(U1102) controls this signal.
Frequency Synthesizer Circuit
The PLL(Phased Locked Loop) block consists of VC-TCXO(TCX1001), PLL in RTR6300 and
VCO(VCO1000). Input reference frequency is generated at VC-TCXO(TCX1001) and the RF
local signal is generated at VCO. PLL compares the two signals and generates the desired
signal with a preprogrammed counter which controls voltage.
VOLTAGE CONTROLLED TEMPERATURE COMPENSATED CRYSTAL OSCILLATOR (TCX1001)
The VC-TCXO (TCX1001) is a reference source of the frequency synthesizer. It provides 19.2MHz
reference frequency to PLL-IC. It is a voltage controlled temperature compensated crystal
oscillator having 19.2MHz ±2.5ppm frequency stability over all useful temperature range.
A correct frequency tuning is made by the control voltage.
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2-3
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