SmVswrCircle

Draws a constant-VSWR (Voltage Standing Wave Ratio) circle — a circle centred on the chart origin that passes through a given impedance point. All points on the circle share the same VSWR as the specified impedance.

Demo

:res 0.50 :react 1.00 :stroke-width 2

:show-point

VSWR ≈ 4.266

Usage

<SmithChart>
  <SmVswrCircle :res="1" :react="1" stroke="#42b883" />

  <!-- Multiple circles -->
  <SmVswrCircle :res="0.3" :react="-0.5" stroke="blue" stroke-width="3" />

  <!-- Hide the impedance point marker -->
  <SmVswrCircle :res="2" :react="0.5" :show-point="false" stroke="red" />
</SmithChart>

Props

Prop	Type	Default	Description
res	Number | String	1	Normalised resistance of the impedance point.
react	Number | String	1	Normalised reactance of the impedance point.
showPoint	Boolean	true	When true, also renders a small marker dot at the impedance point itself.
stroke	String	'black'	Colour of the VSWR circle and the impedance point marker.
strokeWidth	Number | String	3	Width of the VSWR circle stroke in pixels.

How VSWR is calculated

The radius of the VSWR circle equals the distance from the chart centre to the impedance point in the normalised plane — that is, the magnitude of the reflection coefficient |Γ|:

$$ |\Gamma| = \sqrt{a^2 + b^2} $$

where a and b are the normalised Cartesian coordinates of the impedance point (see SmPoint).

VSWR relates to |Γ| by:

$$ \text{VSWR} = \frac{1 + |\Gamma|}{1 - |\Gamma|} $$

The demo above shows the live-computed VSWR value as you drag the sliders.