Interactive Smith chart
The Smith chart looks confusing at first, but it is the key tool for matching. The interactive view shows where an impedance lies, how a line rotates it and how an L-network brings it to the centre.
Open in the browser
No installation, no sign-up needed.
What the page does
- Enter an impedance, see its position on the chart
- Reflection coefficient and SWR as a circle around the centre
- Line transformation as rotation
- L-network matching with component values
- Exercises with worked solutions
Background
Every point on the Smith chart corresponds to a normalised impedance z = Z / Z₀. The centre is a perfect match, the edge total reflection. A piece of lossless line rotates the point on a circle of constant SWR around the centre; half a wavelength is one full turn. An L-network of an inductor and a capacitor brings any load to the centre in two steps.
In practice
How it works: enter a load impedance, for example 25 + j15 Ω on a 50 Ω line. The point appears on the chart, and the circle around the centre shows the SWR. Lengthening the line moves the point clockwise on that circle. The L-network calculation suggests two paths to the centre and gives the required component values.
Frequently asked questions
Why do I need the Smith chart?
For matching antennas and amplifiers and for understanding what an antenna analyser shows.
Are component values calculated?
Yes, for L-network matching inductance and capacitance are given at the chosen frequency.