Tait TB9100, Инструкция по установке и эксплуатации, Страница: 109 / 144

TB9100 Installation and Operation Manual Technical Description 109
© Tait Electronics Limited May 2006
8.3 PA Module Operation
The TB9100 PA is a modular design with the circuitry divided among
separate boards which are assembled in different configurations in different
models. Interconnect boards are used in certain models to connect boards
that are physically separated on the heatsink. The 5, 50 and 100 W PAs are
available for operation on 28 VDC, while the 5 and 50W PAs are also
available for operation on 12 VDC.
Figure 8.12 on page 111 shows the configurations of a 100W 28V PA and a
50W 12V PA, along with the main inputs and outputs for power, RF and
control signals.
RF Circuitry
The RF output from the reciter is fed first to the 6 W driver board. In the
100 W model the output from the 6 W driver board is fed into a –3 dB
hybrid coupler on a separate splitter board and then to two 60 W final boards
in quadrature. The outputs from these two boards are then combined by
another –3 dB hybrid coupler on a separate combiner board before being fed
to the low-pass filter (LPF)/directional coupler board.
In the 50W model, the output from the 6 W driver board is fed to one 60 W
final board and then to the LPF/directional coupler board. In the 5W
model, the output from the 6W driver board is fed directly to the LPF/
directional coupler board.
Control Circuitry
The microprocessor located on the control board monitors and controls the
operation of the PA. There are no manual adjustments in the PA because all
the calibration voltages and currents required to control and protect the PA
are monitored by the microprocessor. The software also automatically
detects the PA configuration and controls the PA accordingly.
If any of the monitored conditions exceeds its normal range of values, the
microprocessor will generate an alarm and reduce the output power to a
preset level (foldback). If the measured values do not return within the
normal range after foldback, the PA will be shut down.
The alarms and diagnostic functions are accessed through I
2
C bus messages
on the system control bus via the reciter, control panel and CSS. Some
measurements are logged by the microprocessor and this information can
also be accessed through the system control bus.
The operation of the cooling fan mounted on the front panel is determined
by the temperature limits set in the PA software.
Power Supply
The 100 W PA operates off a 28VDC external power supply only, while the
5 and 50 W PAs can operate off a 28VDC or 12 VDC external power supply,
depending on the model. The 12V PAs are fitted with an internal boost
regulator board (refer to
“Boost Regulator” below).