Notes on Power Combiner and Splitter Circuits

Overview

From APPLIED MICROWAVE & WIRELESS, VOL. 11, NO. 2, FEBRUARY 1999

A power combiner/splitter is either a combiner or a splitter, depending upon the direction the source of power takes. In one direction, it sums multiple sources into a common output; in the other direction, it divides a single source into multiple outputs. Figure 1 is a block diagram of a popular logic circuit. If power is applied to terminal H on the right, then half of the power will appear at terminals 1 and 2. Also, the voltages will have the same phase as that of the source (1=2). Terminal E is isolated from the rest of the circuit because of the choking action of the balun (balanced-to-unbalanced transformer). In-phase (common mode) currents are suppressed. [Some readers may rec ognize this circuit as an RF version of the classic telephone hybrid ed.]

Figure 1: Block diagram of a popular logic circuit.

If power is applied to terminal E, then half of the power will appear at terminals 1 and 2. In this case, however, the voltage at terminal 2 is 180 degrees out-of-phase with terminal 1(1= 2). Terminal H is now isolated from the rest of the circuit because the power splitter becomes a high-impedance choke for the balanced output of a balun.

Note that the 1:2 unun (unbalanced-to-unbalanced transformer) between H and the splitter is necessary...