Samsung SCH-A310 Service Manual page 30

Circuit Description
6-2 PCS Section
6-2-1 Receiver
LOW NOISE AMPLIFIER & DOWN
CONVERTER (U300)
U300 includes LNA and Down Converter and
supports Quad_mode CDMA & AMPS,GPS,PCS.
The low noise amplifier featuring 1.8dB Noise Figure
and 18dB gain amplifies a weak signal received from
the base station to obtain the optimum signal level.
The Gps RF signal is downconverted from 1575.42
MHZ to the common receive IF of 183.6 MHz .Its LO
is generates by a dual-band VCO and PLL circuit
whose other narrowband tunning range supports
both PCS and Cellialr operation.
RF BAND PASS FILTER (F300,F302,F305)
The RF BPF accepts only a specific frequency
(869.04~893.97MHz,1930~1990MHz,1575.42MHz))
from the signal received from the mobile station.
IF SAW BAND PASS FILTER FOR CDMA,FM
(F304,F301)
IF SAW BPF is used for CDMA system having 1.23
MHz wide band and ±630kHz band width. The filter
also eliminates the image product generated at the
mixer.F301 is IF saw band psaa filter for FM
VOLTAGE CONTROLLED OSCILLATOR(U382)
A dual-band VCO generates 1391.82MHz LO and
PLL circuit whose other narrowband tunning range
supports both PCS and Cellialr operation.
SAMSUNG Proprietary-Contents may change without notice
PHASE LOCKED LOOP (U340)
Input reference frequency is generated at VCTCXO
(U380) and the divided signal is generated at VCO.
The PLL compares the two signals and generates the
desired signal with a pre-programmed counter which
controls voltage.
VOLTAGE CONTROLLED TEMPERATURE
COMPENSATED CRYSTAL OSCILLATOR
(U390)
It provides 19.68Hz reference frequency to PLL (U340),
RFT3100(U400), and IFR3300(U300).
A correct frequency tuning is made by the voltage
control.
6-2-2 Transmitter
RFT3100 (U400)
The RFT3100 contains Up converter, Automatic gain
control amplifier(AGC),and Driver Amplifier.
RFT3100 accepts analog data signal, so there is no
need for additional Modulation Circuit.
Up Converter and Driver Amplifier's gain are
controlled through the Serial Bus Interface(SBI).
RF BAND PASS FILTER (F441)
RF BPF accepts only a specific frequency
(1850~1910MHz)from the signal received from the
RFT3100.
6-5