RF Filter Designer & S2P Viewer
Design ideal lumped LC filters, graph S-parameters and import or export Touchstone files.
RF Filter Designer & S2P Viewer
How to use the RF Filter Designer & S2P Viewer
Choose the filter response, topology, order, impedance and cut-off frequencies. Review the calculated ladder and S-parameter graph, or import an S2P file for comparison.
How it works
The filter designer starts with a normalised Butterworth or Chebyshev low-pass prototype, applies the selected frequency and impedance transformation, and calculates a lumped LC ladder. It can substitute the nearest E6, E12, E24, E48 or E96 preferred component values. Its S-parameters are evaluated by cascading the ABCD matrix of every selected series and shunt element.
Example: A third-order 100 MHz Butterworth low-pass in a 50 Ω system produces a three-element LC ladder. Selecting E12 changes its calculated 79.6 nH inductors to available 82 nH values and its 63.7 pF capacitor to 68 pF; the graph and Touchstone export then show the response of those selected values.
What to keep in mind
This is a first-pass synthesis and simulation tool, not a substitute for electromagnetic or production validation. Real inductors and capacitors have finite Q, self-resonance, parasitic reactance and tolerance. PCB transmission lines and grounding become increasingly important as frequency rises.
Frequently asked questions
What does filter order mean?
The order is the number of reactive prototype sections. A higher order creates a steeper transition but uses more components and is usually more sensitive to loss and tolerance.
What is the difference between Butterworth and Chebyshev?
Butterworth has a maximally flat pass band. Chebyshev accepts a selected amount of pass-band ripple to obtain a sharper transition for the same order.
What is an S2P file?
It is a Touchstone two-port data file containing S11, S21, S12 and S22 values across frequency. It can be opened by many RF design and measurement applications.
Which preferred-value series should I choose?
E12 and E24 are common practical starting points. E48 and E96 offer finer choices when suitable precision RF components are available. Always confirm the required value, tolerance, Q and self-resonant frequency with the component supplier.
Can I manufacture directly from these values?
Use the results as a starting point. Round to available component values, include realistic component models, and validate the layout with an RF simulator or network analyser.
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