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6-2 Receiver Section
LOW NOISE AMPLIFIER (LNA)
The low noise amplifier featuring 1.5dB and 16 dB
gain amplifies a weak signal received from the
base station to obtain the optimum signal level.
DOWN CONVERTER (MIXER)
First local signal is applied to this down converter.
The down converter transfers the signal amplified
at the LNA into 85.38 MHz IF signal. 85 MHz IF
signal is made by subtracting 881
signal from 966
12.5MHz first local signal.
RX IF AUTOMATIC GAIN CONTROLLER
(AGC) AMP
85.38 MHz IF signal is applied to IF AGC amp, the
IF AGC output level is applied to BBA (Baseband
Analog ASIC). The IF AGC amp (U302) keep the
signal at a constant level by controlling the gain.
Dynamic range is 90 dB, up gain +45dB, and down
gain -45dB.
RF BAND PASS FILTER (BPF)
The RF BPF (F302) accepts only a specific
frequency (881
12.5MHz) from the signal
received from the mobile station. The band width
is 25 MHz.
IF SAW BAND PASS FILTER FOR AMPS
IF SAW BPF (F304) is used for AMPS system
having 30 kHz channel spacing and
band width. The filter also eliminates the image
product generated at the mixer.
Samsung Electronics - Contents may change without notice.
IF SAW BAND PASS FILTER FOR CDMA
IF SAW BPF (F303) is used for CDMA system
having 1.23 MHz wide band and
width. The filter also eliminates the image product
generated at the mixer.
BUFFER
Buffer (Q342) amplifies signal to be applied to the
local input of the down converter (U301) when a
12.5 MHz RF
phase is locked between VCO (U341) and PLL IC
(U342).
VOLTAGE CONTROLLED OSCILLATOR
The VCO (U341) generates the signal having 966
MHz center frequency and
with the voltage control. PLL IC (U342) controls
this signal.
PHASE LOCKED LOOP (PLL)
Input reference frequency is generated at
VC_TCXO (U343) and the divided signal is
generated at VCO (U341). PLL compares the two
signals and generates the desired signal with a
pre-programmed counter which controls voltage.
VOLTAGE CONTROLLED TEMPERATURE
COMPENSATED CRYSTAL OSCILLATOR
It provides 19.68 MHz reference frequency to the
15 kHz
mobile main set. A correct frequency tuning is
made by the voltage control.
THERMISTOR
The thermistor (U371) detects temperature. It is
used to compensate active component
characteristics due to the temperature difference.
Circuit Description
630 kHz band
12.5 MHz deviation
6-5
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