User's Manual

IV-4
Power Divider/Combiner (internal to each TAU-500 enclosure)
A Wilkinson power divider and combiner are used to split the RF signal into, and combine the amplified
RF signal out of the (2) P300 final amplifier pallets. Flanged power resistors help ensure that any
differences between the inputs or outputs are balanced.
The Wilkinson design takes advantage of the fact that an impedance transformation can take place
across a quarter-wavelength transmission line if the line has different impedance than the source or
load impedances being matched. In this case, quarter-wavelengths of 75-ohm coaxial are used to
maintain 50-ohm impedances at the input and output of the Wilkinson divider/combiner. Due to its
electrical and mechanical symmetry, the Wilkinson design’s performance over moderate bandwidths is
superior to other types. This design maintains phase and amplitude equality, in addition to providing
isolation and matched outputs.
Circulator/Isolator (internal to each TAU-500 enclosure)
A circulator and load termination (popularly described as an isolator) is installed into each TAU-500
directly after the amplification stage and before the directional coupler. RF power will flow through the
isolator in one direction (from the amplifier stage to the directional coupler). RF power applied in the
opposite direction (back into the amplifier stage) will experience a high loss. Hence, the isolator isolates
the TAU-500 power amplifier enclosure from external influences. The potentially damaging reflected
power heading back towards the amplifier stage gets dumped into the flanged termination resistor. In
addition, these reflected signals cannot mix in the amplifier stage and produce intermodulation
distortion products.
Each circulator has a maximum insertion loss 0.5dB and a minimum isolation of 17dB. The load
termination is rated at 250 watts, 50-ohms.