Microwave Power Splitter Design using Resistors

In RF/microwave circuit design, when there are needs of splitting one signal power into two branches over a wide frequency band while the loss is somewhat tolerable, a resistive three-port network can be employed. This applet offers a means to choose the values of the three resistors according to the design goals in terms of return.insertion losses, under the given line impedances which can be different in general.

Brief User' Guide

The user needs to supply the following information:

  • Characteristic impedance at each port, Z01, Z02, and Z03
  • For each of {R1, R2, R3}, specify the range of the resistance value {minimum, maximum} and the number of data points to be sampled. NOTE: Any of the R values can be fixed by
    • enter the constant resistor value in the Rmin entry
    • set the number of points to "1"
  • The applet will choose a number of choices of combinations of {R1, R2, R3} according to the design goals. This number for choices needs to be provided, the default is: NChoice=20
  • The design goals are specified in terms of
    • return losses for S11, S22, and S33
    • insertion losses for S21, S31, and S32
    • NOTE: either a ">" or "<" sign is required in those requirements
    • each criterion is attched a weighting factor which represents the relative importance in the making the selections. A "0" value minimizes the importance of one particular goal

After setting all the input values, a click on the "Calculate" button will trigger a computation over all data points of {R1, R2, R3} while only the NChoice results are kept in arrays which are arranged in order of the degrees comforming to the design goals. And all the selections are plotted in return/insertion losses versus choice indices. A scrollbar offeres a way to inspect the particular selection in more details, i.e., the {R1, R2, R3} and all S-parameters will change according to the current choice index. A click on the "Clear" button erases all previous results.


[1] David M. Pozar, "Microwave Engineering", Chapter 5, Addison-Wesley, New York, 1990.

[2] Robert J. Weber, "Introduction to Microwave Circuits, Radio Frequency and Design Applications", pp.325-326, IEEE Press, New York, 2001.

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