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2-4
Theory of Operation
: UHF1 Transmitter
2.3.2
MODB/VSTBY Supply
The supply to the MODB/VSTBY pin varies depending on the conditions listed in
.
2.3.3
Audio/Signaling
The audio/signalling/filter/companding IC (ASFIC) and the audio power amplifier (
) form the main components of the audio/signalling section of the controller board. Inputs
include a 16.8 MHz clock from the synthesizer, recovered audio and squelch, MCU control signals,
and external or internal microphones. Outputs include a microprocessor clock (CLK), modulator
output to the synthesizer, and amplified audio signals to an internal or external speaker.
2.4
UHF1 Transmitter
The UHF transmitter consists of the following basic circuits as shown in
• Power amplifier (PA).
• Antenna switch/harmonic filter.
• Antenna matching network.
• Power control integrated circuit (PCIC).
Table 2-4. MODB/VSTBY Supply Modes
Condition
Circuit Operation
Radio On
Vddd supply voltage via CR411
Radio Off
• Vddd turned off
• Q416 gate pulled low by R462
• Q416 switched on
• U410 supplies 3.2V to MODB_VSTBY
Primary battery removed
• Vddd turned off
• Q416 gate pulled low by R462
• Q416 switched on
• Lithium-ion battery provides 3.2V to MODB_VSTBY
Figure 2-3. Transmitter Block Diagram
PCIC
Antenna
P A
Antenna Switch/
Driver
Harmonic Filter/
Vcontrol
Vcontrol
From VCO
Jack
PA-Final
Stage
Matching Network
Содержание PR860
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Страница 17: ...1 4 Introduction Radio Model Information Notes ...
Страница 51: ...2 34 Theory of Operation Voltage Control Oscillators VCO Notes ...
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