The "partial resistive divider" (PRD) is often overlooked when selecting a power divider circuit. This article compares its attributes with those of resistive, reactive and Wilkinson divider circuits. Figure 1 shows the basic resistive, reactive, partial resistive divider (PRD) and Wilkinson divider circuits. There are 1 through N equal output branches.
Pros and Cons of the Approaches
Resistive dividers offer minimum size and a perfect match without transformers. The tradeoffs are a path loss twice the split loss, isolation only twice the split loss, a low (1 to 100 mw) input power limit, and only an equal power split.
The PRD match is limited only by the input transformer, which has an impedance ratio of approximately half the number of outputs. The path loss is less than 3 dB more than the split loss. Isolation is twice the path loss and up to 6 dB better than the resistive and reactive divider isolation. The input power handling is more than twice that of the resistive divider, but less than the reactive and Wilkinson circuits. As with the resistive divider, it is limited to equal power divisions.
The reactive divider input power is limited only by the transmission lines; the output power split can be unequal. Its input match is limited only by the input transformer, but that has an impedance transformation twice that of the PRD. Its output VSWR is almost twice the number of outputs. Also, a failure at one of the output loads can short out all the outputs.
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