From More Practical Filters and Couplers: A Collection from Applied Microwave & Wireless

Popular inductive circuits used for power combiners/splitters have the appearance of transmission line transformers but are they?

By Jerry Sevick



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...

Products & Services
Single Phase Transformers
Single-phase transformers output single-phase AC power, typically while stepping-up or stepping-down the voltage between two circuits.
Power Supplies
Power supplies are electrical devices that deliver electric power to one or several loads. They generate the output power by converting an input signal into an output signal.
Board Mount Transformers
Board mount transformers are transformers designed to be embedded in or mounted on computer boards.
DC Power Supplies
DC power supplies accept an input power and output the desired form of DC power. Common types of DC power supplies include linear power supplies, switching power supplies, DC-DC converters, and silicon controlled rectifier (SCR) type power supplies.
Small-Signal Bipolar Transistors (BJT)
Small-signal bipolar transistors (BJT) are semiconductors that amplify small AC or DC signals. They consist of a base n-type or p-type layer sandwiched between emitter and collector layers of the opposite type.

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