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S-Parameter Stuff


S-Parameters have been with us a long time but few of us really have a good feel for them. A modern RF engineer would be "up the creek" if he or she could not manipulate / use / and understand s-parameters.

This page provides links to s-parameter tutorials, application examples, s-parameter tools / demos and manufacturer's s-parameter data files. We hope you will find enough material here to help you get over any "fear" of this important subject!

Contents of This Page

S-Parameter Tutorials
S-Parameter Application Examples
S-Parameter Tools & Demos
S-Parameter Files
S-Parameters Explained
Reference Books on S-Parameters
Explore SSS Online


See Also: Smith Chart Stuff


See Also:
RF Globalnet
RF Globalnet's Demo Software Files
Page with Lots of FREE Design, Analysis and
Modeling "Goodies" inclucing APLAC and RFCAD!



S-Parameters Explained

Tutorial on S-Parameters
Scattering Parameters are the reflection and transmission coefficients between the incident and reflection waves. They describe completely the behaviour of a device under linear condition at microwave frequency range. Each parameter is typically characterised by magnitude, decibel and phase. The expression in decibel is 20log(Sij) because s-parameters are voltage ratios of the waves.

S11: input reflection coefficient of 50W terminated output.
S21: forward transmission coefficient of 50W terminated output.
S12: reverse transmission coefficient of 50W terminated input.
S22: output reflection coefficient of 50W terminated input.

The advantage of s-parameters does not only lie in the complete description of the device performance at microwave frequencies but also the ability to convert to other parameters such as hybrid (H) or admittance (Y) parameters. Additionally, stability factor (K) and many gain parameters can be computed using the following equations:

  • Stability Factor, K: 
         1 + |S11 * S22 - S12 * S21|2 - |S11|2 - |S22|2
K =  ----------------------------------------------
                       2|S12| * |S21|
  • Maximum Stable Gain, MSG 
          |S21|
MSG = -----    (if K < 1)

      |S12|
  • Maximum Available Gain, MAG 
          |S21|
MAG = ----- * (K - SQR(K2 - 1))  (if K > 1)
      |S12|
  • MAXIMUM Unilateral Transducer Power Gain, Gu 
                   |S21|2
Gu = ---------------------------
     (1 - |S11|2) * (1 - |S22|2)
  • Forward Current Gain, h21 
                      - S21
h21 = ---------------------------------
      (1 - S11) * (1 + S22) + S12 * S21

    • Thanks to OKI for this note!



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    S-Parameter Tutorials:

    HP

    Download Agilent's Classic S-Parameter Interactive Tutorial (1400K -- pdf + QT Movie)

    Download Agilent's Classic S-Parameter Interactive Tutorial (1300K -- pdf file only)



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    S-Parameter Application Examples:


    Agilent's Index of Application Notes on S-Parameters


    Agilent's Wireless Design Tips, including application notes and other literature to help the designer. To get here from the link, press "Library" in the small blue box, then "Wireless Library" and scroll down to the bottom


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    S-Parameter Tools & Demos:


    RF Globalnet
    RF Globalnet's New Design Software Files Page


    RF Globalnet
    RF Globalnet's TOP 25 Design Software Downloads Page
    Take the link, then press "Software Downloads" in the middle column. Press "Top 25" and you're there.


    HP

    Agilent's Interactive JAVA-based "Impedance Matching Game"



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    S-Parameter Files:


    RF Globalnet
    RF Globalnet's Online S-Parameter Files Page
    Take the link, then press "Software Downloads" in the middle column. Press "S-Parameters" in the Modeling box on the right and you're there.



    Agilent logo

    Download Agilent's RF & Microwave S-Parameter Data Files
    From this link, press "Library" in the small navy box, the "Wireless Library"; then scroll down the page to "Models" and follow the link to S-Parameter files.



    RFMD

    Download RF Micro Devices' RF & Microwave S-Parameter Data Files


    Infineon's S - Parameters and SPICE Parameters

    Murata S-Parameter Download Service

    Coilcraft S-Parameter and PSPICE Model Files

    Minicircuits S-Parameters





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    Reference Books on S-Parameters:

    Click on a Title Below for a Direct Link to Purchase

    cover
    Buy This Book
    		 Electromagnetic Waves in Stratified Media (Ieee/Oup Series on Electromagnetic Wave Theory), by James R. Wait. Hardcover - 372 pages Reprint edition (July 1995). Our Price: $69.95

    		cover
    Buy This Book
    		 Microwave Circuit Design Using Linear and Nonlinear Techniques , by George Vendelin, Anthony M. Pavio, & Ulrich L. Rohde. Paperback - 784 pages Reprint edition (May 1992). Our Price: $79.95
    cover
    Buy This Book
    		 Microwave Field-Effect Transistors : Theory, Design, and Applications , by Raymond S. Pengelly. Hardcover 3rd edition (December 1995). Our Price: $79
    Shop at Amazon.com!
    		SSS Online is proud to be an Amazon.com affiliate.

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