TB8100 Installation and Operation Manual Circuit Description 19
© Tait Electronics Limited June 2005
System Interface
Board
The reciter can be fitted with an optional system interface board which
provides the links between the reciter’s internal circuitry and external
equipment. The circuitry on the system interface board provides additional
signal processing so that the outputs meet standard system requirements.
Several different types of system interface board are available, although only
one board can be fitted to a reciter at any one time. Each system interface
board can identify itself to the reciter control circuitry.
Power Supply The reciter operates off a +28 VDC (nominal) supply. The supply is fed to
two separate power supplies, one on the RF board and a second on the
digital board. The power supply on the RF board also powers some of the
circuitry on the system interface board.
The power supply on the RF board provides 5.3V and 8.5V regulated
supplies. This 5.3V supply is boosted to 23V and also provides a 3.3V
regulated supply. The power supply on the digital board provides 3.3V and
5.3V regulated supplies. It is also fed through to provide a 2.5V supply.
2.2 PA
The TB8100 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 5W, 50W and 100W PAs
are available for operation on 28VDC, while the 5W and 50W PAs are also
available for operation on 12VDC. Figure 2.3 on page 21 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 6W board. In the 100W
model shown in Figure 2.3, the output from the 6W board is fed into a
–3dB hybrid coupler on a separate splitter board and then to two 60W
boards in quadrature. The outputs from these two boards are then combined
by another –3dB 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 6W board is fed to one 60W board
and then to the LPF/directional coupler board. In the 5W model, the
output from the 6W 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.
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