To: File

From: Jon Hagen

Date: March 2, 2000

Subject: 4-way power splitters

The 4-way power splitters used in the IF system provide equal amplitude and equal phase outputs. The outputs are isolated from each other if the input is driven from a 50-ohm source.

These splitters are a simple tree of hybrids, as shown in Figure 1. The actual circuit is shown in Figure 3 and an equivalent circuit is shown in Figure 2. The right-hand hybrids use simple transformers. They have 50-ohm impedances at their output ports and a 25-ohm impedance at their input port. The left-hand hybrid uses transmission line transformers. Its input port has an impedance of 50-ohms while its output ports have 25-ohm impedances. Either one of these hybrids (or any hybrid, internally terminated for use as an equal-phase 2-way splitter or combiner) can be analyzed as follows: Referring to Figure 4, verify that if V2 = - V3 , then V1 will be zero. The currents at ports 2 and 3 will determine the Zout , the impedance of these ports. Then set V2 = V3 = 1 and calculate V1 . The input impedance will be given by

Zin = Zout V1 2 /2.