CNI CNI-803D, Руководство пользователя, Страница: 4 / 16

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3. Circuit guide
A. RF circuit
CNI-803D circuit is composed of five parts such as power supply, antenna,
synthesis/modulation of frequency, transmission and reception.
1
power supply
Power supply is composed of voltage regulator and switching part. Voltage regulator
generates 3V of power supplied from VBB when the control of RF_EN switch is turned on.
When RF_EN is high, RF_VCC is regulated with 3V, and RF_VCC is supplied to PLL IC,
VCTCXO, OP-Amp(IC102), VCO, and Drive Amp(Q104).
When RX_EN is low, RX_VCC is turned on by Q202, and RX_VCC (3V) is supplied to
LNA, MIXER, IF AMP and IF IC.
When TX_EN is low, TX_VCC is turned on by Q201, and TX_VCC (3V) is supplied to
Buffer Amp(Q105) and OP-Amp(IC104).
The switch between TX mode and RX mode can be achieved by control of RX_EN(Q202)
and TX_EN(Q201).
2 Antenna
Antenna part is composed of antenna matching circuit, BPF, and Rx/Tx signal isolation
circuit.
CNI-803D adapts

/4 WHIP antenna to match to mid range frequency of communication.
TX/RX signal isolation circuit isolates signals of communication and is composed of
switching diode and inductor.
The signals received from antenna meet the send/receive path and then D1 is turned on
and the signals proceed only to receiving path. In receiving mode, signals from TX Power
Amp can not go through RX path because D101 is off. (refer to RF circuit diagram)
3 Frequency synthesizer and modulator
Frequency synthesizer consists of PLL part, VCO module and pre-modulation filter. The
PLL part is composed of phase detector, loop filter, and 12.6Mhz VCTCXO
VCO module generates 806~821Mhz frequencies in accordance with the voltage which is
from charge pump of PLL to loop filter. Programmable Divider in PLL makes the VCO
output frequency to any channel value according to the frequency data from Logic CPU.
Phase detector gets low and high frequencies from comparison of phase. Loop filter filters
the frequencies to get a value of voltage. The voltage is input to VCO to achieve phase
lock process.
Modulation is completed when modem IC signal of Logic part is input to VCO and
authorized.
4 Receiver