Impedance matching networks
Design L-networks (both topologies, both solutions), Pi and T networks for a chosen Q, single shunt-stub matches and quarter-wave transformers for any load, with component values at the frequency, the loaded Q and bandwidth, and a check of the resulting input impedance.
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How to use it
Enter the frequency, the source resistance and the load (R + jX). Each tab designs a network and checks it by computing the input impedance of the result.
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L-network — two elements, two solutions (Pozar, Microwave Engineering, §5.1). When the load resistance is above the source, the shunt element goes across the load; when it is below, the series element goes next to the load. The loaded Q is fixed by the resistance ratio. A low-pass solution (series L, shunt C) also attenuates harmonics.
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Pi network — two L-networks back to back through a virtual resistance lower than both ends, so you choose the Q (and with it the bandwidth and harmonic attenuation). The classic amplifier output tank.
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T network — the dual, through a virtual resistance higher than both ends.
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Single stub — the distance from the load and the open- or short-circuit stub length, in wavelengths and centimetres for your cable’s velocity factor (Pozar §5.2).
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Quarter-wave transformer — Z₁ = √(Z₀·RL) and the bandwidth for a chosen maximum |Γ| (Pozar eq. 5.48).
Check value: matching 200 − j100 Ω to 100 Ω at 500 MHz gives 0.92 pF shunt with 38.8 nH series, or 46.1 nH shunt with 2.61 pF series — Pozar’s Example 5.1.
Related: Smith chart (watch the match step by step), feedline and SWR, winding the inductors.
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