Samsung SCH-i830 Service Manual page 9

Circuit Description
2-3. CDMA Section
2-3-1. Receiver
Low Noise Amplifier(U1000)
The low noise amplifier(It is included FC7510: U1000) amplifies a weak signal received from
the base station to obtain the optimum signal level.
RF Band Pass Filter(F1000)
The RF BPF(F1000) passes only a specific frequency(881.49±12.5 MHz) from the signal
received from the mobile station. The bandwidth is 25 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 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.
VC-TCXO(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.
2-5
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