Plot a load, build a matching network, and inspect its impedance and frequency response.
Move over the chart to inspect Z, Y, and Γ.
Arrow keys move the inspection cursor; Enter applies the selected click action. Chart labels are normalized. Grid changes do not rotate the physical load point.
Calculation order: load → element 1 → element 2 → generator. The schematic shows physical order from input to load.
Electrical lengths are specified at the design frequency. Physical length = (θ / 360°) × c × VF / f₀. VF changes the displayed physical length, not a length already entered in degrees.
| Stage | Impedance Z (Ω) | Normalized z | |Γ| | Return loss (dB) |
|---|
Manual sweep holds the entered load impedance constant. L/C reactances and electrical line lengths change with frequency.
Response plot shows input reflection magnitude in dB (negative), the effective one-port S11. Return loss is its positive counterpart. Plot floor: −60 dB.
| Marker | Frequency | Zin (Ω) | VSWR | Return loss (dB) |
|---|---|---|---|---|
| Select a frequency and pin a marker to compare points. | ||||
Design links include manual inputs, matching elements, and sweep settings. Imported measurements stay local and must be re-imported by the recipient.
Set the real system impedance Z₀ and design frequency. Enter Z, Y, or reflection data, or import a Touchstone trace. Open and short circuits can be entered as |Γ| = 1 at 0° and 180° respectively.
z = Z / Z₀ y = Y × Z₀
Γ = (Z − Z₀) / (Z + Z₀)
Z = Z₀ × (1 + Γ) / (1 − Γ)Add series/shunt inductors or capacitors, a lossless line, or an open/short shunt stub. The matching path and stage table update at the selected frequency. L-match suggestions target a real Z₀ and are recalculated from the current network input.
Zseries = Z + jX
Yshunt = Y + jB
Γin = ΓL × e^(−j2βℓ) when Zc = Z₀A manual sweep assumes the same complex load at every frequency; it does not predict an antenna’s changing impedance. Import measured S11/S22 to use the measured frequency dependence. Imported data is evaluated at its actual sample frequencies, without extrapolation.
VSWR = (1 + |Γ|) / (1 − |Γ|)
Return loss = −20 log₁₀ |Γ|
Reflected power = |Γ|² × 100%Export the chart as SVG, numerical results as CSV, or the transformed one-port response as S1P. Then verify with real component models and a VNA. Ideal exact matches can show infinite return loss; this is a mathematical limit.
Supported files: Touchstone legacy 1.x or 2.0, 1/2-port single-ended full matrices, RI/MA/DB, common real port reference. Noise sections, mixed-mode/triangular matrices, active selected-port responses, and unequal port references are rejected with an explanation.
This is a passive, linear, ideal one-port matching tool. It excludes component Q/ESR, self-resonance, tolerances, PCB parasitics, line attenuation and dispersion, and active-device gain/noise/stability optimization. Matching a complex source for maximum power is a separate problem; the target here is the real chart reference Z₀. Total reflection has infinite VSWR. At a perfect match the reflection phase is undefined. Accepted power and mismatch loss are not antenna efficiency.
Open stubs add +j tan(βℓ)/Zc susceptance; shorted stubs add −j cot(βℓ)/Zc. For a general lossless line, Zin = Zc (ZL + jZc tan βℓ) / (Zc + jZL tan βℓ). Increasing length need not follow a constant-|Γ| circle when Zc differs from chart Z₀.
Technical references: Ohio State: chart geometry · Microchip AN4061: matching · IBIS: Touchstone specification
← More RF calculatorsAlso available for iOS, Android, and Windows.
Screenshots and app details →
