RF Matching Network Range

This post will show you how to measure the Range of an RF Matching Network in 9 easy steps.


Step 1 - Connect an inline power meter, the Octiv Mono ( mono 1) to the output of a 50Ω load. We are going to measure the range with power applied so make sure the load can handle the power. The power meter is optional but it will be useful if you want to measure the Efficiency of the Network.
mono match

Step 2 - Connect the impedance meter, an Octiv Mono ( Mono 2 ), to the input of the Match Network. Yes! the input, we are putting the power through the Matching Network the wrong way.

Step 3. - Connect the impedance meter to an RF power supply. In this example we are using a 13.56 MHz generator.

Step 4. - Set the generator to the maximum power that the generator can tolerate in reflected power. In this example we use 50W.

Step 5. - Set the power and impedance meters to 10 samples per second and start the trend mode on both meters.

Step 6. - Sweep the tune capacitor on the Matching Network though its full range slowly so that the meter records lots of points.

Step 7. - Sweep the load capacitor on the Matching Network through its entire range from min to max.

Smith Chart

Step 8 - Sweep the tune capacitor back to its starting position.

Step 9 - Sweep the load capacitor back to its starting position.

The full test will take a few minutes to complete. The impedance data can now be plotted. First we look at the impedance of the inverted Matching Network on a Smith chart. The impedance measured looking into the Matching Network is the complex conjugate of the load impedance.

To get the Load or Plasma impedance save the data from mono 2 to an excel file and reverse the sign of the imaginary component of the impedance. Now plot the impedance on a x-y plot with x being the real resistance and the y being the imaginary impedance.

Match Load Impedance Range

So there we have it. The range of the Matching Unit is the enclosed area. We can now work out the Matching Network Quality . The resistance of the load ranges from 3Ω to 10Ω, so the quality Q, ranges from 2 to 4. We can show that the efficiency of the Matching Network is a function of the Q factor.