Formula used
Series impedance uses Z = R + j(ωL − 1/ωC). Parallel circuits first calculate admittance, then invert it. Resonance occurs when inductive and capacitive reactance cancel.
The reflection coefficient is Γ = (Zin − Z0)/(Zin + Z0). Return loss equals −20 log10|Γ|. VSWR equals (1 + |Γ|)/(1 − |Γ|).
A lossless transmission line uses Zin = Z0(ZL + jZ0 tan βl)/(Z0 + jZL tan βl). Matching values use classical real-resistance L-network approximations. Production designs require electromagnetic verification.
How to use
- Select a simulation mode and RF circuit type.
- Enter operating frequency, source, load, and component values.
- Configure sweep, transmission-line, noise, and matching options.
- Add custom elements when modelling a cascaded RF network.
- Run the simulation and review impedance, gain, VSWR, plots, and warnings.
- Copy results or export CSV, PDF, history, and configuration data.
Example data
| Application | Frequency | R | L | C | Reference Z |
|---|---|---|---|---|---|
| 100 MHz series resonator | 100 MHz | 2 Ω | 100 nH | 25.33 pF | 50 Ω |
| 433 MHz matching study | 433 MHz | 5 Ω | 18 nH | 7.5 pF | 50 Ω |
| 2.4 GHz transmission line | 2.4 GHz | 0 Ω | 0 nH | 0 pF | 50 Ω |
Frequently asked questions
What does this RF simulator calculate?
It estimates impedance, admittance, gain, return loss, VSWR, resonance, matching values, transmission-line behaviour, noise, stability, and simplified S-parameters.
Is it a replacement for professional RF software?
No. It is an educational lumped and transmission-line calculator. Production designs need measured component models and electromagnetic simulation.
Why can results differ from laboratory measurements?
Real components include package parasitics, self-resonance, layout coupling, conductor loss, dielectric loss, connector effects, and manufacturing tolerance.
What reference impedance should I use?
Most RF systems use 50 Ω. Some broadcast and video systems use 75 Ω. Use the impedance required by your equipment.
What does a low return loss mean?
A low positive return-loss value indicates a larger reflection. Higher return loss generally means a better impedance match.
What VSWR is acceptable?
Requirements vary by system. Values near 1:1 are best. Many practical systems target below 2:1.
How is resonant frequency calculated?
For ideal L and C values, f0 = 1/(2π√LC). Losses and parasitics shift the measured resonance.
What is Rollett stability factor?
Rollett K helps assess two-port stability. K greater than one is normally considered with the determinant condition.
Can I design an L matching network?
Yes. The calculator suggests ideal series and shunt reactances for positive real source and load resistances.