Samsung SCH-570, Service Manual

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5-5
VOLTAGE CONTROLLED OSCILLATOR (VCO,
U341)
The VCO (U341) generates the signal having 966
MHz center frequency and 12.5 MHz deviation
with the voltage control. PLL IC (U342) controls
this signal.
ANTENNA
Antenna allows signals and sends to receive from
the base station.
PHASE LOCKED LOOP (PLL, U342)
Input reference frequency is generated at
VC_TCXO (U343) and the divided signal is
generated at VCO. PLL compares the two signals
and generates the desired signal with a pre-
programmed counter which controls voltage.
VOLTAGE CONTROLLED TEMPERATURE
COMPENSATED CRYSTAL OSCILLATOR (VC-
TCXO, U343)
It provides 19.68 MHz reference frequency to PLL.
A correct frequency tuning is made by the voltage
control.
DUPLEXER (F301)
Duplexer (F301) controls to transmit through the
antenna only the signals within acceptable Tx
frequency range (836 12.5 MHz) and to receive
through the antenna only the signals within
acceptable Rx frequency range (881 12.5 MHz).
It also matches LNA input in receiving part and
PA output in transmitter part with the antenna.
POWER SUPPLY REGULATOR (U123)
The power supply regulator generates a regulated
power.
THERMISTOR (R498)
The thermistor (R498) detects temperature. It is
used to compensate active component
characteristics due to the temperature difference.