Power dividers and power splitters differ in how their splitting resistors are arranged:
- A power divider forms a symmetrical three-resistor network, each resistor being 50⁄3Ω (≈ 16.67Ω).
- A power splitter uses two 50Ω resistors in a symmetrical configuration.
Impedance Analysis
In a power divider, every port is loaded by a 50⁄3Ω resistor. Looking into any port with the other ports terminated with 50Ω, we will see an impedance of 50Ω:
\begin{aligned}
Z_{\text{in}}
&=\frac{50}{3}\Omega+\Bigl(\bigl(\tfrac{50}{3}\,\Omega+50\,\Omega\bigr)\parallel\bigl(\tfrac{50}{3}\,\Omega+50\,\Omega\bigr)\Bigr)\\[4pt]
&=\frac{50}{3}\Omega+\frac{\Bigl(\tfrac{50}{3}\,\Omega+50\,\Omega\Bigr)}{2}=50\,\Omega
\end{aligned}
In a power splitter, only the output ports carry 50Ω resistors. Looking into the input port from the signal generator, with the two output ports terminated in 50Ω, the impedance seen will also be 50Ω:
\begin{aligned}
Z_{\text{in}}
&=(50\Omega + 50\Omega) \parallel (50\Omega + 50\Omega)\\[4pt]
&= \frac{50\Omega + 50\Omega}{2}=50\Omega
\end{aligned}However, if we look into either output port of the power splitter with the remaining ports terminated with 50Ω, the impedance will be:
\begin{aligned}
Z_{\text{in}}
&=50\Omega+\bigl((50\Omega+50\Omega)\parallel50\Omega\bigr)\\[4pt]&=50\Omega+\bigl(100\Omega\parallel50\Omega\bigr)\\[4pt]
&=50\Omega+\frac{100\Omega\cdot50\Omega}{100\Omega+50\Omega}=50\,\Omega+33.\overline{3}\,\Omega=83.\overline{3}\Omega
\end{aligned}
Practical Applications and Usage Guidelines
If a power divider is used for leveling or ratio measurements — where one half of the split signal is monitored and the other drives the device under test — the impedance from the source to the splitting node is 50⁄3Ω, resulting in a 3 : 1 VSWR and a significant mismatch.
In contrast, when a power splitter is used, no resistor lies between the signal source and the splitting node. Therefore, the source can be treated as an ideal zero-impedance source, and the VSWR becomes 1:1.
Use the three-resistor power divider when you simply need to split power; choose the two-resistor power splitter for ratio measurements and leveling applications.
Please note that Mini-Circuits power splitter/combiners are power dividers as defined in this article. When every port is terminated with the reference impedance (e.g. 50Ω or 75Ω), each port will also present the reference impedance.
Mini-Circuits power splitter/combiners are ideal for laboratory test setups, system signal distribution, antenna beam-forming, and any application requiring wideband, low-VSWR power division with excellent amplitude and phase balance.
For assistance in selecting the best device for your application, please contact us. Our team is ready to support you at every stage of your project.