RF Circuit Studio
Draw a two-port RF circuit, edit component values and see its ideal S-parameter response update live.
RF Circuit Studio
How to use the RF Circuit Studio
Drag or tap parts into the schematic, then connect their terminals with Wire mode. Select any part to edit its value and orientation; the ideal two-port response updates automatically once P1, P2 and ground form a valid circuit.
How it works
RF Circuit Studio is a visual first-pass simulator for passive two-port networks. Parts placed on the schematic are converted into a nodal admittance model at every sweep frequency. Resistors, ideal inductors and capacitors use their frequency-dependent impedances; a transmission line uses its characteristic impedance, physical length and velocity factor. Selectable voltage probes can add realistic resistive and capacitive loading while reporting node magnitude and phase under a defined source and termination. The resulting two-port admittance matrix is converted into S11, S21, S12 and S22 for the selected reference impedance.
Example: The starting example is a 100 nH series inductor followed by a 10 pF shunt capacitor between 50 Ω ports. Drag either part, select it to change its value, or add another part and connect it with Wire mode. The insertion-loss and return-loss traces move immediately, and the same sweep can be downloaded as an S2P file.
What to keep in mind
The simulation deliberately uses ideal components and lossless transmission lines. Probe presets use a simplified parallel input-resistance and input-capacitance model, plus a first-order bandwidth estimate for the displayed probe output. Ground-lead inductance, compensation networks and detailed frequency-dependent input impedance are not included. Use it to explore topology and measurement loading, then repeat the design with manufacturer models and verify the physical assembly with suitable instruments.
Frequently asked questions
What do P1 and P2 represent?
They are the input and output reference planes of a two-port network. Each must connect to the circuit, and the circuit also needs a ground reference.
How do I connect parts?
Select Wire, then choose two terminals. You can also drag a terminal close to another terminal to make a snapped connection. A green terminal is connected; an open terminal is not.
Why does the graph say the circuit is incomplete?
The simulator checks for exactly one P1 and one P2, a ground reference, useful passive parts and a valid electrical path. This prevents a plausible-looking graph from being shown for a floating, shorted or disconnected drawing.
How is the transmission-line delay calculated?
Electrical length is calculated from physical length, frequency and the chosen velocity factor. Use the cable or substrate manufacturer’s value when available.
Do voltage probes change the simulated circuit?
Yes, unless Ideal is selected. A loaded probe adds its selected resistance and capacitance from the test node to ground, so the S-parameters and node voltage can both change.
What does a TP graph trace show?
Each TP trace plots RMS tip-voltage magnitude in dBV, where 0 dBV equals 1 V RMS. It shares the graph with S-parameters for convenient frequency comparison, but dBV is an absolute voltage level while an S-parameter is a ratio.
What does the Will’Tek 1205 preset model?
It uses the published 500 ohm nominal RF loading and a conservative 1 pF capacitance, together with 10:1 voltage attenuation and a 3 GHz specified-bandwidth estimate. The original specification states less than 1 pF at 1 MHz, so the preset can be edited when better fixture or measured data is available.
Can I use the downloaded S2P file in another RF program?
Yes. The export is a standard Touchstone two-port file in magnitude-angle format. It represents this tool’s ideal simulated circuit and selected sweep, not a measured device.
Does this replace KiCad or an electromagnetic simulator?
No. It is a quick schematic and ideal network simulator. KiCad remains appropriate for capture and PCB layout, while electromagnetic and circuit tools with vendor models are needed for production-level RF verification.
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