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RP3000 Circuit Description
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3) Antenna Switch and LPF
Output signal from RF amplifier passes through a low-pass filter network and a transmit/receive
switch circuit comprised of D101, D201 and D202 before it reaches the antenna terminal. D201 and
D202 is turned on (conductive) in transmit mode and off (isolated) in receive mode.
4) APC
The automatic power control (APC) circuit stabilizes the transmit output power by detecting the
drain current of final stage amplifier FET. IC100 (2/2) compares the preset reference voltage with
the voltage obtained from final current. APC voltage is proportional to the difference between auto
detect voltage and reference voltage output from IC100 (1/2). The output voltage controls FET
power amplifier and keeps the transmitter output power constant. The output voltage can be varied
by the microprocessor, which hence controls the transmitter output power.
5. Signalling Section
The block diagram of signaling section is shown as figure 5.
D601
LIMITTER
X601
BASEBAND PROCESSOR
IC601
BBP_IRQN
BBP_RPL
SP
MIC
SW
Q700
AF PA
IC710
SW
Q710
MIC
AUDIO_EN
EXT
_
SPK+
EXT_MIC
BBP_CSN
BBP_CMD
BBP_CLK
Q701
SW
EXT
_
MIC_SEL
EXT
_
SP_SEL
IC605
BUFFER
Ver
Vbias
COMPANDER
IC603
BYPATH
MOD
MB
COMPRESSOR EXPANDER
AF PA
MIC_F
B
AUDIO
IC606
BUFF AMP
Vbias
IC611
FILTER
Fig.5 AF and Signalling Circuit
In the transmit section, CTCSS/CDCSS signaling are produced by MCU and DTMF/2-Tone/5-Tone
by IC601 under the control of MCU. Signalings then enter VCO together with AF signal from MIC
for modulation.
In the receive section, after buffer amplified together with IF demodulation signals, the signallings
enter CPU and IC601 respectively for decode.
Содержание RP3000
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