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Circuit Description
5-2 RF Part
5-2-1 Transmitter
(For CDMA (800MHz))
ANTENNA
Antenna sends the signal to the base station and
receives the signal from the base station.
DUPLEXER
The duplexer (F401) passes RF signal with the
frequency of 836.49 ± 12.5 MHz through power
amp output to antenna, and receives RF signal
with the frequency of 881.49 ± 12.5 MHz from
antenna to LNA input.
POWER AMP
The power amplifier module (PAM, U447) amplifies
the power of the RF signal sent to the base
station through the antenna.
RF Band Pass Filter (Tx RF SAW Filter)
The RF BPF (F400) pass only specific frequency
(836.49 ± 12.5MHz) signal. This filter eliminates the
image products generated by the up-converter.
TX Automatic Gain Control Amp
The TX AGC amp within RFT6122 controls its gain
by adjusting the control voltage in order to deliver
the suitable power needed at the input stage of
Driver amp. Dynamic range is 90dB, and its control
voltage varies from 0.2V to 2.5V.
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5-2-2 Receiver
(For CDMA (800MHz))
LOW NOISE AMPLIFIER (LNA)
The low noise amplifier included in RFR6122
amplifies a weak signal received from the base
station to obtain the optimum signal level.
RF BAND
PASS FILTER (RX RF SAW
FILTER)
The RF BPF (F300) passes only specific frequency
(881.49±12.5 MHz) signal.
RX Automatic Gain Controller (AGC) AMP
RX AGC amplifier within RFR6122 keeps its output
power at a constant level by controlling the gain
within the dynamic range of 90dB, maximum gain
45dB and minimum gain -45dB.
5-2-3 PLL Block
FREQUENCY SYNTHESIZER CIRCUIT
While both RX PLL block and TX PLL block are
embedded in RFT6122, only the RX VCO block is
embedded
in
RFR6122.
frequency is generated from VC-TCXO (OSC301),
and the RF local signal from VCO. PLL compares
the reference with the VCO output divided by
multiples preprogrammed in counters through SBI
interface, and, if the difference is found, adjusts
the DC voltage which controls the frequency of
VCO output signal.
5-4
The
input
reference
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