Axcera INNOVATOR, Инструкция по эксплуатации

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UHF Analog Driver/Transmitter/ Chapter 4, Circuit Descriptions
Translator
LX Series, Rev. 3 4-15
rejection mixer consisting of U1, U2, U3
and U6. The 44 MHz IF input is
connected to the board at J2, and then
to the image rejection mixer. This mixer
converts the 44 MHz input to an output
frequency of 1044 MHz. The output of
the mixer is amplified by U4 and applied
to a band pass filter consisting of C2-C4
and some microstrip line sections. This
filter rejects any LO leakage at 1 GHz
and also any unwanted out of band
products. The output of the filter is
amplified by U5 and then filtered before
exiting the board at J1.
4.4.4 (A4) Upconverter Control
Board (1304760; Appendix B)
This board performs a variety of
functions, which include an interface
between the other boards in the
upconverter and the rest of the
transmitter. It also has a
microcontroller U8, which controls and
monitors the functions of the other
boards in the assembly.
The microcontroller communicates via
an RS-485 interface with the
transmitter's system control module. It
reports any faults and metering
information and receives channel
information, which it passes along to the
PLLs on the L-Band PLL Board and the
First Conversion Board.
The board also generates various
voltages used by the rest of the boards
in the upconverter. U9 converts the
+12V input to the board to +20V. U15
co12V to +5V for the on board
10 MHz crystal oscillator. U12 converts
+12V to +9V for the L-Band PLL board
and the First Conversion board. U13
and U14 ge5V for the
microcontroller.
The board also selects whether the
internal or external 10 MHz reference
source will be used. There is an
onboard 10 MHz oscillator, U3, which is
used when no external 10 MHz source is
present. The Relay K1 is automatically
switched to the external 10 MHz reference
whenever it is present. The LED DS1
illuminates whenever the internal 10 MHz
reference is used. The diode detector CR1
detects the presence of the 10 MHz
external reference that connects to U2,
which compares the detected level to a
reference level and switches the relay
whenever the reference is present. It also
disables the internal oscillator whenever
the external 10 MHz reference is being
used.
The output of the relay is split to drive
multiple outputs, some internal and some
external. The external outputs leave the
board at J1-22C and J1-31B and are used
by the external receiver and modulator
modules.
The board also contains AGC circuitry,
which controls a pin diode attenuator on
the Downconverter Board. There are
three references used by the AGC circuit.
The first is the AGC reference #1, which
comes from the transmitter's driver
module. The second is the AGC reference
#2, which is a diode ORed sample of the
output stages of the transmitter. The IC
U5 normalizes the level of the AGC
reference # 1 and sets it at a level that is
0.2V less than the level of AGC reference
#2. The AGC reference #1 and #2 are
diode ORed with only the highest
reference used by the AGC circuit.
The highest reference is compared to the
ALC reference, whic h originated on the IF
processor module, and the error voltage
generated by U4D and applied to the
external pin attenuator. The AGC will try
to maintain a constant ratio between the
ALC voltages and the higher of the two
AGC voltages. If something in the output
amplifier of the transmitter fails, the AGC
reference #1 voltage will take over and
the power will be regulated at the output
of the driver.