curve fitting for input and output matching

Hi, In this video (https://www.youtube.com/watch?v=3l6Xmtg558w) he says he used curve fitting for input matching. I came to know for broadband matching I should deal with impedance curves rather than points. Could anyone elaborate the idea of curve fitting for input and output matching and also how to synthesize the matching networks that fit the impedance curve or any detailed material?. Thanks

Use Stable_model() in Verilog-A.

If you use Keysight ADSsim, use Data Access Component.