User's Manual

Innovator CU0TD-1/CU0RD-1 – CU4TD/CU4RD Board Descriptions
ATSC Transmitter/Regenerative Translator
Instruction Manual, Rev. 1 62
(A6-A3) Dual BLF888A Pallet Assembly (1315347)
This board is a UHF LDMOS power amplifier consisting of two pair of power
transistors operating in parallel. The board operates on a power supply voltage
of +48VDC. The voltage regulator U1 steps down the voltage to provide a bias
voltage to each pair of transistors. The diodes CR1 and CR3 are used to
temperature compensate the bias voltage that is applied to the Q1 and Q2 RF
transistor pairs. As the transistor pairs heat up, the diodes also heat up, causing
the voltage across them to drop, lowering the bias voltage to the RF transistors
so that the voltage remains constant with device temperature.
The board has a gain of approximately 18 dB. The RF input to the board is split
by HL1 and each output is connected through hybrid couplers to the Q1 and Q2
transistor pairs. The amplified outputs of the transistor pairs are connected
through hybrid couplers to the combiner HL2. The transistor pairs are operated
in quadrature, with one transistor pair operating 90° out of phase of the other,
which provides for a very good return loss across the UHF band on both the input
and output of the board.
(A6-A5) DC/DC Converter Board (1315335)
The DC/DC Converter Board provides the +12VDC needed to operate the 1 Watt
Amplifier board in the assembly. The DC/DC Converter Board acts as a switching
supply using U7 and the Q1 MOSFET. The switching voltage is applied to the
primary of the T1 Transformer. The AC output of the transformer is rectified by
CR1 and filtered before the +12 VDC is connected to the output of the board at
J3-3. A feedback path is provided through the other two coils of the transformer
which is fed to the IC U7 to maintain the oscillation.
(A7) Output Detector Board (1308685 or 1312207 in the CU0TD/RD-2 thru
CU0TD/RD-5)
The (1308685 and 1312207) output detector boards are identical in operation except the
(1312207) board can be used as either an average, for digital, or peak, for analog,
detector board using jumpers on J5 and J6. The (A7) Output Detector Board provides
forward (2V=100%) and reflected (2V=25%) power samples to the CU Control Board for
metering and monitoring purposes. R7 is the reflected power calibration pot and R23 is
the forward power calibration pot. A Forward power sample, -10 dBm, connects to J4 on
the board, which is cabled to the front panel sample jack of the drawer. The RF output
of the board, typically +46 dBm, is at J2, which is cabled to J9 the RF Output Jack of the
drawer.
(A8) Control Card, Innovator CX (1312543)
The Innovator CX control board provides the overall system control for the CXB system.
There are two main elements of the board, U7 and U9. U7 is a programmable logic
device that is loaded with firmware, which provides the overall system control. It
decides whether or not to allow the system to generate RF output power, and turns the
+32 VDC power supply on and off depending on whether or not it is receiving any faults,
either faults generated on board, or faults generated externally. The second major
component of the board is the microcontroller U9, which controls the front panel
indications and drives the display. The U9 microcontroller is not involved in the decision