User Manual

System Components
Figure 9 – RF Final Circuit Board Layout
The RF. final Circuit board layout for an individual module is shown in Figure
9. Should the Final Stage ever require replacement, the entire assembly,
including the heat spreader, is easily replaced as a subassembly.
This combined output signal is fed to a low pass filter, which also incorporates
RF detector circuit to determine voltages from the forward and reflected
power levels at the output of PA. These detector outputs are used to provide
an alarm in the event that a high VSWR is present at the output of the power
amplifier.
The output of the low pass filter attenuates high frequency components of the
desired signal, (i.e. harmonics). The output of the low pass filter is connected
to semi-rigid coaxial cable, which is attached to the RF output N connector of
the amplifier.
The pre-amp stage generates about 12-16 Watts. The Pre-amp RF power
then passes through a dual splitter assembly to drive four final stages; each is
capable of generating up to 80 Watts to a total of 320 Watts of RF. power.
This output is then passed through a dual combiner stage and then through a
low pass filter to generate up to 250 watts of RF. power.
The design of the low pass filter utilizes special low loss high dielectric
constant materials with high thermal conductivity. The back of the low pass
board also employs a heat spreader to minimize the board surface
temperature. The inductive elements of the filter are simple half-loop
elements that are soldered directly to the circuit board. The directional
couplers for forward and reflected power measurement are etched into the
filter board design. The final output connector is soldered directly into the
filter assembly. The geometry of the low pas filter board is shown in Figure
10.
Version 3 3-13 07/18/01