Theory of Operation: Main Board 3-3
3.1 Main Board
The main board performs the transmitter and receiver functions necessary to translate between
voice and data to modulated radio-frequency (RF) carrier at the antenna. The main board contains
all the radio’s RF circuits for the following major components:
• Receiver
• Transmitter
• Frequency Generation Unit (FGU)
• Controller
Figure 3-2, Figure 3-3, Figure 3-4 and Figure 3-5 illustrates the VHF, UHF1, UHF2 and 700/800 MHz
transceiver block diagrams.
Figure 3-2. Transceiver (VHF) Block Diagram (Power and Control Omitted)
FGU
Transmitter
Receiver
2nd
LO
Termination
Antenna Switch
coupler
Rev
Power
Detector
Current
Sense
FET
TRIDENT IC
LOOP
FILTER
PRESCALAR
BUFFER
RX SSI Data
16.8MHz
BUFFER
PRE
BUFFER
TX LO
TX
BUFFER
TX
RX
16.8MHz
RX SSI Clock
RX SSI Frame Sync
Indicates Sub-shield
Harmonic
Filter
Driver
Amplifier
Abacus
IF Filter
15dB Step Attn
RX VCO
TX VCO
VHF
LNA
VHF
Mixer
Circuit
Current
Sensor
Batt. DC Supply
o
DC Supply to FET PA & Driv. Amp.
Power Control Voltage (Vctrl)
VHF
RX LO
GPS
To Next Page
Loading...
Need help?
General
