Broadband impedance matching network is used in almost all kinds of microwave/RF circuits, in order to reduce reflection, or increase output power.

Here is a TRUE free software (free of charge, also free of tedious registration) dedicated for broadband impedance matching network design and optimization. This software is named IMNLab. It is a numerical based optimization tool and can match any complex-valued port impedance to the ideal impedance (50/75 Ohm or any other special target impedance) over a broadband.

Here is the homepage located at WordPress:
https://imnlab.wordpress.com/

You can download IMNLab installer package and tutorial documents freely from the homepage.

 

Just some comments. IMNLab can be used to solve two common RF engineering problems:
1. Reduce power loss between two RF blocks;
2. Control returnloss for the front-connectors.

More details can be found in the homepage:
https://imnlab.wordpress.com/