2: System Overview
2-8
PRC1099A-MS
First LO - MX1
Transmit
Down-converts 75 MHz IF signal
to selected channel frequency.
Inputs 75 MHz IF from75 MHz
filter Y1.
Inputs 76.6 to 105 MHz LO1 from
Synthesizer board at SYN1.
Output to transmit current
regulator U1.
Receive
Up-converts selected channel
frequency to 75 MHz IF signal.
Inputs 20W receive signal at the
selected channel frequency from
the Audio/Filter board.
Inputs 76.6 to 105 MHz LO1 from
Synthesizer board at SYN1.
30 MHz
Low-Pass Filter
Transmit
Filters transmit/receive signal for
unwanted image and spurious
responses above 30 MHz.
Input transmit signal at selected
channel frequency from MX1
mixer.
Output to transmit amplifier U1.
Receive
Inputs receive signal at selected
channel frequency from
Audio/Filer board.
Outputs to MX1 mixer.
MMIC Transmit
Amplifier - U1
Transmit
Amplifies 1.6 to 30 MHz transmit
signal.
Inputs transmit signal from
30 MHz LPF.
Outputs to PA board through
J1-A2.
Voltage Regulator
- Q3
Transmit
Provides a constant current
source to transmit amplifier U1 in
transmit mode.
12V from the Junction
board.
Outputs constant 100 mA to U1.
Power Amplifier Board
Predriver - U1
Transmit
Class A amplifier amplifies
transmit signal to the necessary
level for Q2 and Q3 drivers.
Inputs transmit signal from Mixer
board.
Outputs amplified transmit signal
to driver amps Q2 and Q3.
Driver Amps - Q2,
Q3
Transmit
Push-pull amplifiers in class AB
configuration; drive the signal for
power amplifiers.
Inputs transmit signal from
predriver U1.
Outputs to transmit signal to RF
power amps Q3 and Q4.
Power amplifiers -
Q4, Q5
Transmit
Power amplifiers in class AB
configuration; provide final RF
output of 5 or 20W.
Inputs transmit signal from driver
amplifiers Q2 and Q3. Output to
LP filters on Audio/Filter board.
Table 2-1 Board Functionality (continued)
Function
Path
Description
I/O